UNIVERSITY OF CALIFORNIA 
 
 COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY, CALIFORNIA 
 
 CIRCULAR No. 284 
 April, 1925 
 
 THE ALMOND IN CALIFORNIA 
 
 By R. H. TAYLOR and G. L. PHILP 
 
 INTRODUCTION 
 
 The almond (Prunus communis) is supposed to be native to the 
 countries around the Mediterranean. It is related to the peach which 
 it resembles in manner of growth and character of blossoms and 
 leaves. The wood, however, is much harder and the tree lives longer 
 under equally favorable conditions. The fruit Jias a thin, leathery 
 pericarp or hull, which corresponds to the thick, fleshy portion of the 
 peach, and which splits upon ripening and generally opens when 
 dry, exposing the nut inside. 
 
 ALMOND PRODUCTION AND DISTRICTS 
 
 The production of almonds in the United States is confined almost 
 entirely to California, where over 99 per cent of the crop is raised. 
 With the 1915 crop the production entered upon what appears to be 
 a long prospective increase. The large acreage of almonds set out 
 in the past few years is the result of greatly improved market con- 
 ditions which are due to the successful work of the California Almond 
 Growers' Exchange. According to recent figures, 1 there are now 
 approximately 100,000 acres of bearing and non-bearing trees and 
 large acreages are still being planted. 
 
 Table 1 gives, by counties, the comparison of the number of acres 
 in bearing in 1909, with the bearing and non-bearing acreages for 
 1923. 
 
 * This circular is a revision, by the junior author, of California Agr. Exp. Sta. 
 Bull. 297, by R. H. Taylor. 
 
 i California Crop Eeport, Calif. State Dept. Agr., Special Publication 43, p. 21, 
 1924. 
 
2 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 TABLE 1 
 
 Comparison of Bearing Acres of Almonds in the Various Counties in 19092 
 with the Bearing and Non-Bearing Acres in 1923 
 
 
 Bearing acres, 
 
 Bearing acres, 
 
 Non-bearing acres, 
 
 County 
 
 1909 
 
 1923 
 
 1923 
 
 Alameda 
 
 246 
 
 400 
 
 
 Amador 
 
 
 14 
 
 7 
 
 Butte 
 
 1051 
 
 5133 
 
 572 
 
 Calaveras 
 
 
 23 
 
 7 
 
 Colusa 
 
 201 
 
 3200 
 
 5900 
 
 Contra Costa 
 
 2613 
 
 2500 
 
 522 
 
 Fresno 
 
 
 84 
 
 167 
 
 Glenn 
 
 359 
 
 2703 
 
 217 
 
 Kern 
 
 
 170 
 
 80 
 
 Kings 
 
 
 15 
 
 5 
 
 Lake 
 
 103 
 
 300 
 
 346 
 
 Los Angeles 
 
 962 
 
 1062 
 
 166 
 
 Madera 
 
 
 141 
 
 108 
 
 Marin 
 
 
 10 
 
 7 
 
 Mendocino 
 
 
 11 
 
 
 Merced 
 
 214 
 
 3321 
 
 599 
 
 Monterey 
 
 
 2400 
 
 150 
 
 Napa 
 
 234 
 
 20 
 
 23 
 
 Placer 
 
 144 
 
 389 
 
 20 
 
 Riverside 
 
 272 
 
 1432 
 
 53 
 
 Sacramento 
 
 829 
 
 2376 
 
 551 
 
 San Benito 
 
 87 
 
 130 
 
 8 
 
 331 
 
 26 
 
 San Bernardino 
 
 7 
 
 San Diego 
 
 185 
 
 San Joaquin 
 
 1212 
 
 5592 
 
 481 
 
 San Luis Obispo 
 
 116 
 
 8489 
 
 21,987 
 
 San Mateo 
 
 323 
 
 6 
 
 2 
 
 200 
 
 60 
 
 4 
 
 Santa Barbara 
 
 1 
 
 Santa Clara 
 
 160 
 
 Shasta 
 
 
 Siskiyou 
 
 
 3 
 
 3 
 
 Solano 
 
 1228 
 
 1776 
 
 126 
 
 Sonoma 
 
 
 25 
 
 15 
 
 Stanislaus 
 
 421 
 
 4170 
 
 1080 
 
 Sutter 
 
 769 
 
 2090 
 
 32 
 
 Tehama 
 
 411 
 
 662 
 
 24 
 
 Tulare 
 
 
 832 
 731 
 
 46 
 
 Ventura 
 
 57 
 
 Yolo 
 
 1862 
 
 5554 
 
 2000 
 
 Yuba 
 
 39 
 
 290 
 
 60 
 
 All other counties 
 
 827 
 
 
 
 The State 
 
 14,541 
 
 56,646 
 
 35,794* 
 
 * Estimated acreage planted in state, 1923, 5,921 not included. 
 
 2 Figures for 
 144, 1919. 
 
 1909 from Calif. State Board of Hort., Mo. Bull., vol. 8, no. 4, 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 It is interesting to note that the bearing acreage is confined mainly 
 to the upper part of the great interior valley, extending from Tehama 
 County on the north to Merced County on the south. The largest 
 proportion of the non-bearing acreage is confined to San Luis Obispo 
 County, where the almond is being extensively planted. Figure 1 
 shows the location of the almond plantings. 
 
 .S ( S K I YOU 
 
 MODOC 
 
 FT 
 
 S H A S T A I 
 
 l ' T E H _A 
 
 ^ t 
 *1 
 
 •\l 
 
 
 ALMONDS 
 ACREAGE III CALIFORNIA 
 
 EACH DOT = 500 ACHES. 
 Leading Counties by acres: 
 San Luis Obispo 30,476 
 
 Colusa 9,100 
 
 Yolo 7,544 
 
 San Joaquin 6,073 
 
 Butte 5,705 
 
 THE STATB (Bearing) 56,646 
 
 (Non-bearing) 35,794 
 
 * X V 
 
 SJPSSX& 1 f \ ° \ From California Crop 
 
 •^llV'o° tUMNE A^ *\ Report - 1923 
 
 
 N 
 
 -V 
 
 V 
 
 V 
 
 \ 
 
 Leading Counties 
 
 Based on Average Pro due- 
 tion 
 
 nta barbaraI *V \ 
 
 SAN B ERNARO I N 
 
 1st. Butte 
 
 2nd. Yolo 
 
 3rd. (San Joaquin 
 
 (San Luis Obispo 
 8th. Colusa 
 
 From California Crop Reporting Service 
 June 3, 1924. 
 
 IMPERIAL 
 
 Fig. 1. — Outline map of California showing the almond acreage by counties. 
 Each dot represents 500 acres. The leading counties based on average production 
 are also listed. 
 
 While California produces practically all the almonds grown in 
 the United States, there are millions of pounds imported into this 
 country every year. Table 2 gives the quantities of almonds brought 
 into the United States during the years 1917 to 1923, inclusive : 
 
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 TABLE 2 
 Almond Imports. Crops of 1917 to 1923a 
 
 Imports for 
 
 Crops of 
 
 Pounds 
 Unshelled 
 
 Pounds 
 Shelled 
 
 Total pounds 
 
 1917-18 
 
 1917 
 1918 
 1919 
 1920 
 1921 
 1922 
 
 4,278,990 
 6,733,512 
 7,355,894 
 6,622,340 
 4,637,002 
 4,719,348 
 
 19,561,155 
 23,594,915 
 26,326,245 
 13,816,044 
 26,705,621 
 22,973,337 
 
 23,840,145 
 30,328,427 
 
 1918-19 
 
 1919-20 
 
 33,682,139 
 
 1920-21 
 
 20,438,384 
 
 1921-22 
 
 31,342,623 
 
 1922-23 
 
 27,692,685 
 
 
 Since the cost of producing almonds in Europe and of transport- 
 ing them to the Atlantic seaboard is low, the Californian grower must 
 become thoroughly familiar with the most economical methods of 
 production and marketing. 
 
 HABITS 
 
 The almond is the first of the deciduous fruit trees to start growth 
 and come into bloom in the spring, and is normally the last one to 
 shed its leaves in the fall. In other words, it has a very short period 
 of rest. When the trees are forced into premature dormancy by mites 
 or lack of moisture, they reach the end of their normal rest period 
 before the winter season is over. Then the first warm weather in 
 spring will bring the trees into bloom. In some cases where moisture 
 and temperature conditions are favorable late in the fall, they may 
 actually blossom before the winter season begins. In young trees 
 that have become dormant unusually early, the rest period may term- 
 inate and the tips of the branches resume growth and continue slowly 
 to develop new leaves at the terminals throughout the winter. Trees 
 which have been kept growing until the leaves have been forced to 
 fall by the cold weather and frosts of winter, do not usually blossom 
 so early in the spring. 
 
 Young trees blossom somewhat later than older ones, and buds on 
 sucker growth blossom later than those on the more mature portions 
 of the same tree. The difference may amount to three or four days 
 or almost a week. Well grown trees carry large numbers of blossoms 
 over the entire tree. 
 
 3 Figures from the California Almond Growers ' Exchange. 
 
ClRC. 284] THE almond IN CALIFORNIA 5 
 
 The wood of the almond is very hard and strong, enabling the 
 tree to bear the weight of heavy crops where proper pruning has been 
 given during the first years of growth. As with other fruit trees, 
 the almond is subject to heart-rot and needs care to prevent the check- 
 ing and cracking of large wounds and consequent infection with decay 
 organisms. The hardness of the wood makes it excellent fuel, and 
 when old orchards are being dug up, the returns from the sale of 
 wood often more than pay for the expense of digging and cutting up 
 the trees and burning the brush. 
 
 The nuts are of two general classes — sweet and bitter. The former 
 is primarily the almond of commerce, though the latter is used largely 
 in the manufacture of almond oil and almond flavoring, as well as 
 in the manufacture of prussic acid. The bitter almond is also much 
 used in nurseries as a rootstock upon which to bud the almond and 
 some other fruits. 
 
 FACTORS LIMITING PRODUCTION 
 
 While the almond is in many ways an easy tree to grow it is 
 rather particular in certain pollination, climatic, and soil require- 
 ments. 
 
 POLLINATION 
 
 Tufts and Philp 4 found that all of the varieties of almonds they 
 tested are self-sterile. This list includes the Big White Flat, Califor- 
 nia, Drake, Eureka, Golden State, Harriott, I. X. L., Jordan, King, 
 Klondike, Languedoc, Lewelling, Ne Plus Ultra, Nonpareil, Peerless, 
 Princess, Reams, Sellers, Silver Shell, and Texas. 
 
 In addition certain almond varieties are inter-sterile. For 
 example, the I. X. L. and the Nonpareil proved practically inter- 
 sterile. The Languedoc and the Texas are inter-sterile as shown by 
 two seasons' work. 
 
 In order to insure cross-pollination it is necessary therefore to 
 interplant varieties which not only are inter-fertile but blossom at 
 about the same time. The accompanying chart (fig. 2) gives the 
 average blooming periods of certain almond varieties. The date of 
 bloom is of course dependent upon many factors, such as soil, season, 
 and location. 
 
 4 Tufts, W. P., and Philp, G. L., California Agr. Exp. Sta., Bull. 346, 1922. 
 
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 
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Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 Figure 3 gives the period of effective bloom of certain almond 
 varieties for the year 1917 growing under the same conditions. 
 Satisfactory pollinizers for various varieties are listed below : 
 
 1. For California — Nonpareil and Drake. 
 
 2. For Drake — California, Ne Plus Ultra, Nonpareil, and Texas. 
 
 3. For Eureka — Nonpareil. 
 
 4. For Harriott — Ne Plus Ultra. 
 
 5. For I. X. L.— Ne Plus Ultra. 
 
 6. For Languedoc — Drake. 
 
 Period oJ 
 
 Effective 
 
 FEBRUARY 
 
 fcl 
 
 OJJC 
 
 ming 
 
 c 
 
 f Almonclj- 
 
 MARCH 
 
 Ui\i\ 
 
 erji ty 
 
 K\riT| - 
 
 -m7. 
 
 
 12 
 
 13 
 
 14 
 
 15 lb 
 
 17 
 
 18 1? 
 
 20 
 
 21 
 
 22|23[2^|25 
 
 Zb 
 
 27!es 
 
 1 
 
 213 
 
 h 
 
 5 
 
 <o 7 
 
 8 
 
 IT 
 
 10 
 
 1 1 
 
 12 
 
 13 
 
 14 
 
 15 
 
 16 
 
 17 1 18 19 2021 
 
 22 
 
 :■:■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 NePfcw Ultra. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I.X.L 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Peerle«/j 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Jordan 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^^^^i 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Laurelling 
 California, 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Won pare il 
 Golden Jlafe 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 biwke 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 i , i 
 
 
 
 
 
 
 
 
 
 
 
 Laijcjueclec 
 
 Tex<w 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 K 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Iyeanu/ 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 12 
 
 13 
 
 \M 
 
 15 
 
 lb 
 
 17 
 
 16 
 
 \1 
 
 20 
 
 21 
 
 ■ ,- 
 
 2<< 
 
 25 
 
 24 
 
 27 
 
 25 
 
 i 
 
 2 1 3 h p| fe 7|6 ? 1 10 |ll |l2li3|i 1 ii;5 l lfe;i7 I8;i<? 20:2 1,22,23 
 
 Fig. 3. — The effective blooming period of certain almond varieties during the 
 season of 1917. The dates in this table cover the time each variety was in con- 
 spicuous bloom and therefore of maximum attraction to insects. From Bull. 346, 
 Calif. Exp. Sta. 
 
 7. For Ne Plus Ultra — California, I. X. L., Jordan, and Non- 
 pareil. 
 
 8. For Nonpareil — California, Drake, Jordan, Ne Plus Ultra, 
 Peerless, and Texas. 
 
 9. For Beams — Texas. 
 
 10. For Texas — Drake and Nonpareil. 
 
 There are a few other suggestions concerning pollination of 
 almonds which are listed below : 
 
 (a) Pollinizing agencies, such as the honey bee, are necessary to 
 set a good crop of nuts. 
 
 (6) One colony oi; honey bees to each acre of orchard insures a 
 proper transmission of pollen. 
 
8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 (c) To facilitate cross-pollination and convenience in harvesting, 
 it is best to plant two, three, or four rows of one kind and then a 
 similar number of the other variety. When a smaller number of the 
 pollinizer is desired, two rows to every four rows of the standard 
 variety can be planted. 
 
 (d) When it is desired to reduce the number of pollinizing trees 
 to the minimum, one tree in twenty-five is perhaps sufficient, although 
 at least one tree in eight is strongly recommended. This can be done 
 by planting the pollinizing variety as every third tree in every third 
 row. Such an arrangement, however, makes it difficult to avoid 
 mixing varieties in harvesting. 
 
 (e) Planting several varieties also assists greatly in lengthening 
 the harvest season and thus enabling an individual to handle larger 
 crops with fewer men and less equipment. For example, the four 
 best varieties, the Nonpareil, I. X. L., Ne Plus Ultra, and Drake, ripen 
 in the order named : the Nonpareil ripening about two weeks before 
 the I. X. L., the Ne Plus Ultra about a week after the I. X. L., and 
 the Drake about two weeks after, the Ne Plus Ultra. 
 
 CLIMATE 
 
 Heat. — Where the conditions of soil and moisture are favorable, 
 the almond will endure the intense heat of the interior valleys and 
 even of the Imperial Valley, provided it is pruned properly to shade 
 the main branches and prevent sunburn. If trees are opened up 
 suddenly to the intense heat of the summer sun, they are apt to sun- 
 burn, but if this opening up is done gradually, the bark will become 
 inured to the new conditions without danger. The nuts grow and 
 ripen more satisfactorily in the greater heat of the interior than 
 along the coast. 
 
 Frost. — The almond tree is hardy and can endure without injury 
 fully as much cold as the hardiest peach. Trees are found growing 
 well in Illinois, Nebraska, Ohio, New York, and other Eastern states. 
 In very favorable seasons they may even bear fruit, though this 
 happens very seldom, because of their habit of blooming before the 
 spring frosts are over. The first Avarm weather seems to start the 
 trees into bloom, especially where the enforcd dormant season of 
 winter is very long. 
 
 While the wood is relatively hardy, the blossoms on the other hand, 
 are very tender. There is a great range in the degree of frost which 
 causes injury, depending largely upon the condition of the tree 
 during the time that the fruit-buds are forming and developing, as 
 
CIRC. 284] THE ALM oND IN CALIFORNIA 9 
 
 well as upon the duration and severity of the frost. Buds and 
 blossoms on trees which have been forced into premature dormancy, 
 either by lack of moisture or by severe attacks of red spider, are much 
 more susceptible to frost injury than those on trees which have con- 
 tinued growth late enough in the fall to provide for the proper devel- 
 opment and maturity of the buds. After differentiation of fruit-buds 
 commences in the summer, the almond leaves should remain on the 
 tree until late into the fall in order to strengthen and develop the 
 fruit-buds and store up elaborated food material for their normal 
 development through the winter. Studies of almond buds gathered 
 from healthy trees which held their leaves until late fall frosts at 
 Davis, showed the first evidence of differentiation of fruit or flower- 
 buds about mid- August, while the flower was not completely developed 
 until early February of the next year, following. During the interven- 
 ing time, development proceeded unchecked through the winter even 
 though the tree was apparently dormant. During the time the crop is 
 ripening on the trees, little is done toward storing food material for 
 the buds. If the leaves turn yellow or drop soon after harvest, the 
 trees do not have the opportunity of storing a sufficient supply of 
 plant food for their normal requirements and the buds are insuf- 
 ficiently nourished during the winter period. The resulting buds are 
 weakened, and the indications are that they are unable to endure 
 unfavorable climatic conditions in the spring, such as light frosts, 
 continued cold weather, or sudden changes from warm to cold. 
 
 The most tender stage in the blossoming and development of the 
 young fruit seems to be immediately after the dropping of the calyx 
 lobes and when rapid growth begins. The blossom becomes more and 
 more tender as it opens. Blossoms with the petals exposed but not 
 yet opened have been known to stand a temperature of 24° F., and 
 blossoms with petals beginning to fall have stood 28° F. No records 
 are available as to the duration of these temperatures. In other cases, 
 blossoms with the petals falling have been killed by temperatures of 30° 
 and 31° F. It must be remembered in this connection that the almond 
 blooms earlier than other orchard fruits and, therefore, is often sub- 
 jected to much more severe frosts than occur during the blooming 
 period of the later fruits. The greatest injury is likely to occur when 
 the frost follows one or more days of warm weather. When the mean 
 temperature both day and night remains low, frosts that might other- 
 wise kill the flowers or setting fruit do no harm. This is what 
 occurred in February, 1917, at the University Farm, when repeated 
 frosts at blooming time did no harm whatever. 
 
10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Freedom from frost and adequate air drainage are closely related. 
 The lands along the lower foothills immediately above the floor of the 
 valleys and the lands along the built up banks of rivers are less 
 subject to frost because the cold air flows from them to the lower 
 lands adjacent. For this reason, the planting of almonds in the lower 
 lands of the valleys, no matter how large the valleys may be, should 
 be avoided. An exception may be the locality which has been 
 thoroughly tested as to frost occurrence for a long period of years 
 and has proved to be frost free, because of some peculiar situation 
 with favoring air currents or air drainage, such as might exist near 
 a natural draw in the hills where the settling of the cold air in some 
 portions of the adjacent valley might be prevented. Such locations 
 are generally confined to very small areas. Sometimes an opening or 
 draw in the hills may serve as an outlet for the drainage of much 
 colder air from considerably higher elevations beyond, and then the 
 danger from frost is very greatly increased. This is very common 
 where canons act as drains to conduct the cold air from the high 
 Sierras to the valleys below. 
 
 Variable weather conditions, especially as regards temperature in 
 the spring after growth commences, are undesirable. At this time 
 sudden changes of weather, even without frost, often destroy the 
 crop. However, it is probable that most of the dropping of fruit 
 when the size of peas or larger, is due to improper pollination. 
 
 Humidity. — Foggy or moist weather during ripening or harvest- 
 ing promotes the growth of molds and consequent darkening of the 
 shells, which then require much heavier bleaching. It also prevents 
 the rapid and thorough drying-out of the kernel, which when moist 
 absorbs sulfur fumes and sometimes become rancid in less than six 
 months. 
 
 Much damp weather in spring encourages the growth of "shot- 
 hole" fungus in the blossoms and fruit, often causing the loss of a 
 considerable portion of the crop. The loss of leaf surface from this 
 fungus is also sometimes so great as materially to affect the vigor and 
 vitality of the tree. 
 
 Rainfall. — The average amount of rainfall which will maintain the 
 trees and enable them to bear regular crops depends on its annual 
 variations, its distribution throughout the year, the time and intensity 
 of the rains, the character of the weather following, and the ability 
 of the soil to receive and retain them. Ordinarily, however, with the 
 above factors favorable, it is conceded that where the winter rainfall 
 averages sixteen inches, almonds can generally be grown, although 
 
ClRC. 284] THE ALM0ND IN CALIFORNIA 11 
 
 not always very satisfactorily, without irrigation, if the orchardist 
 exercises reasonable care in conserving the moisture for the use of 
 the trees. Where the rainfall is inadequate, some means of irrigation 
 must be found to make up the deficit. 
 
 In some sections the annual rainfall varies greatly from year to 
 year. Often it falls in such a way that a large proportion of it is 
 lost in the surface run-off. In many places the soil is so leachy that it 
 is incapable of holding sufficient water for the use of the trees 
 throughout the summer, much of the winter rainfall being lost in the 
 underground drainage. Under any of these conditions, forty inches 
 of rainfall might not be sufficient. 
 
 Continued rainy, damp, and cold weather at blooming time is apt 
 to destroy the pollen and thus prevent the fertilization without which 
 a crop is impossible. Such weather also prevents insects from work- 
 ing, particularly bees, which are the principal means of pollinating 
 almonds. 
 
 Soil. — The almond is a deep-rooting tree which draws heavily 
 upon the plant-nourishing elements of the soil. In ripening the large 
 number of fruits which it is required to do, the tree must draw upon 
 a considerable area of soil in order to supply the large amount of 
 mineral matter that is needed to develop and mature the seeds. 
 Analyses of almonds made by Colby 5 show, when compared with other 
 commonly grown fruits and nuts, that the almond tree leads in the 
 total quantity of mineral matters withdrawn from the soil. Colby 
 states that ' ' The stone fruits fall much below the almond in total ash 
 (mineral matter) excepting the olive, the ash of which, however, is 
 largely silica (nearly eight-tenths), an ingredient so plentifully dis- 
 tributed in all soils that it is of no pecuniary value." 
 
 Hardpan. — Compacted substrata in the soil, whether they be hard 
 clay layers or cemented layers of silicous, ferruginous or calcareous 
 origin, are objectionable. Not only do they keep the roots from 
 foraging to a considerable depth as they normally tend to do, but 
 they prevent proper drainage and aeration of the soil. If such 
 layers are comparatively thin, that is, not more than one or two feet 
 thick at the most, they may be shattered with dynamite so as to allow 
 the moisture, air, and roots to penetrate to better soil below. Hard- 
 pan, therefore, should be avoided when it is too thick to be broken 
 up or where it is not underlaid by desirable soil. 
 
 Humus. — A plentiful supply of humus in the soil is essential. It 
 not only improves the physical condition of the soil, but assists drain- 
 age and moisture retention and renders the plant food available for 
 
 s Colby, Geo. E., California Agr. Exp. Sta., Ann. Kept., pp. 142-159, 1898. 
 
12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 the use of the trees and for the maturing of full crops. Many 
 orchards are very light producers because of a deficiency of humus 
 in the soil. 
 
 Drainage. — The almond root is very particular as to its air and 
 moisture requirements in the soil. It suffers from standing water in 
 the soil especially during the growing season. Exclusion of air by 
 excessive moisture is believed to be one of the most productive causes 
 of "sour-sap." If allowed to continue for any considerable length 
 of time, such a condition will cause the death of many or even of all 
 the roots and, with them, the top. 
 
 Water Table. — A factor which is very commonly overlooked in 
 connection with the natural drainage of almond lands is the position 
 of the water table at different seasons of the year. Great care must 
 be exercised to choose a location where the water table does not rise 
 during the summer. This is a very serious problem in many irrigation 
 sections. Where the Avater table during the winter months is less than 
 twelve feet in depth, it is desirable to have as little fluctuation as 
 possible. Where fluctuations take place at a greater depth than 
 twelve feet, they are not generally serious. The ideal condition is one 
 where the water table is highest in the winter and quickly drops, after 
 the winter rains are over, to a depth of from ten to twelve or fifteen 
 feet, remaining at that point during the remainder of the growing 
 season. 
 
 The soil in addition to being well drained, must be sufficiently 
 retentive of moisture to supply the tree throughout a long, dry grow- 
 ing season. If the soil will not retain a sufficient amount of the winter 
 and spring rains, recourse must be had to irrigation to supply the 
 deficiency. 
 
 Alkali. — Alkali lands are unsuited to almond culture and should 
 be carefully avoided. 
 
 To summarize the soil requirements for almond culture : the ideal 
 almond soil is a deep medium loam, uniform in texture, or nearly so, 
 well drained, and yet retentive of moisture for the use of the tree 
 during the summer. Fortunately, some of the best almond soils are 
 situated along river banks where the land is relatively high, and is, 
 therefore, less subject to frost. 
 
 The various requirements of growth and production are those 
 mentioned above. Often these conditions may be approached in a 
 relatively shallow soil. It is essential to understand that trees, while 
 growing and bearing on shallow soils in some localities, do so because 
 of other exceptionally favorable conditions; either the soil is unusually 
 
CIRC. 284] THE ALM0ND IN CALIFORNIA 13 
 
 well drained and yet sufficiently retentive of moisture, or the humus 
 in the soil is plentiful and the roots are able to work into the partially 
 decomposed rock underlying it for moisture and for some plant food. 
 In such localities the trees may bear comparatively well because of 
 exceptional freedom from frost in the spring. They are generally 
 smaller, however, than those on the deeper, richer soils, and where 
 other conditions are equal, they bear crops in proportion to their size. 
 
 PROPAGATION 
 
 Orchard almond trees are never grown from seed, which do not 
 reproduce the type, but they are propagated by budding desirable 
 varieties on seedling roots in the manner commonly employed in 
 nursery practice for the peach and other stone fruits. The grower 
 should consider carefully what rootstocks to select. 
 
 Rootstocks. — There is still much to learn regarding the behavior 
 of the different roots under varying conditions when used as stock 
 for the almond, but sufficient information has already been gathered 
 to warrant certain recommendations. A survey of the California 
 nurseries in 1922 showed that 72 per cent of the almonds were propa- 
 gated on almond root and 28 per cent on peach root. 
 
 Almond Root. — Most almonds in this state are on almond roots. 
 Where favorable soil, moisture, and drainage conditions exist the 
 almond root is best. It will live in comparatively dry soils, but will 
 not make a tree of large size or bear good crops if the conditions are 
 too dry. 
 
 Where irrigation is not available, and the soil is deep and of 
 proper texture, sufficient moisture may be retained in most years to 
 enable the tree to grow and bear fruit. When extra dry years come, 
 though the almond root may not enable the tree to grow or produce 
 better than would another kind of root, it will carry the tree over a 
 few dry seasons as well as or better than any other. Then, when suf- 
 ficient moisture does come, the almond root is ready to start the tree 
 off on its normal course with the least loss of time. 
 
 The bitter almond is often recommended as being superior to the 
 sweet almond as a stock. This has never been proved. Experiments 
 indicate that there is as much variation among the bitter almond 
 seedlings grown from seed from different trees as there is among 
 seedlings from sweet almonds. Both are equally subject to attack by 
 gophers. There is no reason therefore for preferring one to the other 
 provided healthy, vigorous trees are obtained. 
 
14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 
 
 Peach Boot. — Where the soil moisture varies much in different 
 parts of the orchard, or from time to time during the growing season, 
 the peach root is sometimes the most satisfactory. Soils less than six 
 feet deep, or with gravelly or hardpan layers at lesser depths, are 
 often unsatisfactory for the almond root, and under these conditions 
 the peach root may be better. The peach root is a little better where 
 irrigation is practiced during the summer, and especially where there 
 is danger of an excess of water remaining too long in the soil. The 
 peach does not thrive with standing water around its roots, but will 
 better withstand fluctuating or temporary extremes in water supply 
 than the almond. Its union with the almond is entirely satisfactory. 
 
 Davidiana Root. — Within the past seven or eight years the United 
 States Department of Agriculture has introduced the seed of a 
 Chinese peach, Prunus davidiana, the root of which is more resistant 
 to alkali than that of the ordinary peach. This has been found to 
 unite readily with the almond, although experiments have not yet 
 gone far enough fully to determine its true value. It gives promise, 
 however, of being a desirable stock for sections where alkali may be 
 troublesome. 
 
 Unsuitable Boots. — The Myrobalan plum has frequently been 
 recommended as a stock for the almond on poorly drained soils. The 
 two make a strong union, but the plum root grows much more slowly 
 than the almond top, showing that the trees on Myrobalan root are 
 pinched-in below the union. Even young trees show the same effect. 
 Almond trees on Myrobalan root do not make such large trees nor do 
 they bear such satisfactory crops in any portion of the state where it 
 has been possible to compare them with the same varieties on other 
 roots in similar situations. 
 
 The apricot is occasionally recommended because of its strong, 
 thrifty growth, but the union is not satisfactory. The trees grow well 
 for awhile, but before they reach full bearing, they generally break off 
 at the union through the leverage of the swaying top in even moderate 
 winds. 
 
 Top-working Old Trees. — Where the varieties in an old orchard 
 are unsuitable it is often advisable to work over old trees to more 
 desirable varieties. This may be done by grafting or budding. The 
 general practice is to cleft-graft the large branches at a convenient 
 height from the ground with two or more scions, according to the size 
 of the limb. On branches where the scions fail to grow, it is advisable 
 to save several of the suckers and bud into these. Generally it is 
 advisable to leave a branch asa a sap puller, ' ' which may be removed 
 the year after the grafting. In windy sections where there is con- 
 
CIRC. 284] THE ALMOND IN CALIFORNIA 15 
 
 siderable danger of the scions being blown out, it is advisable to graft 
 about half of the tree, one season, leaving the other half of the top 
 to serve as a windbreak until the top-worked portion has a chance to 
 unite solidly. The other half of the tree may then be top-worked the 
 following year. 
 
 It is sometimes desirable to top-work the orchard with some other 
 fruit. Most stone fruits, particularly prunes, plums, and peaches, 
 unite readily with the almond. The apricot, however, cannot be suc- 
 cessfully top-worked on it. 
 
 CULTURE 
 
 Planting. — Before planting almonds the land should receive the 
 same careful preparation needed by other fruits. Special care must 
 be taken to insure thorough aeration of the subsoil by breaking up all 
 hardpan, plow-pan, or other compacted layers in the soil, where 
 possible. 
 
 Distance. — Almonds in most soils should be planted about thirty 
 feet apart. In rich, deep soils the trees quickly fill the intervening 
 space, the roots occupying the entire soil area long before the tops 
 touch. In poor, shallow soils, or soils deficient in available moisture, 
 the trees may not occupy the entire area above ground, but their roots 
 will require more lateral feeding space to enable the trees to attain 
 the size and bear the crops they should. 
 
 Trees planted too close together often exhaust the moisture of the 
 soil before the growing season is over. This shortage of moisture, 
 and mites — commonly called red spider — cause loss of the leaves 
 long before the normal period for falling. Under such conditions the 
 fruit-buds are unable to make the vigorous growth they should, and 
 are unable to endure without serious injury the degree of frost or 
 the other unfavorable conditions that stronger buds withstand. 
 
 The trees must have plenty of sunlight. If planted too close 
 together, they grow too high, each striving for the light which is avail- 
 able only from above. - In figure 4 the upward tendency of the trees 
 is clearly shown. Such trees, if properly pruned, have a much greater 
 tendency to send out numerous water-sprouts than trees which have 
 plenty of room for the tops to expand laterally. After the tops of the 
 trees interlock and shut out the sunlight from the lower portions, 
 the smaller branches and fruit spurs in these parts gradually weaken 
 and die, and eventually the entire crop is produced on or near the 
 tops of the trees, where alone direct sunlight is available. The exces- 
 sive upward growth of the trees, with the consequent forcing of the 
 
16 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 fruit bearing to the top, not only greatly increases the difficulty and 
 cost of pruning, spraying, and harvesting, but reduces the possible 
 bearing surface of the trees. 
 
 Setting the Trees. — To secure a uniform and vigorous stand, the 
 utmost care is necessary in setting out the trees. The holes should be 
 dug just deep enough and wide enough to accommodate the roots 
 without crowding, after they have been properly trimmed. The 
 actual size of hole will be determined by the size of the average root 
 
 Fig. 4. — Almonds planted twelve feet apart. Trees in very weak condition 
 and almost entirely defoliated by mites before harvest. The few nuts ripening 
 on the trees are small ' ' sticktights. ' ' Photograph taken September 21, 1915. 
 
 system. As a rule, for the medium sized, one-year-old tree, a hole 
 about fourteen inches wide and about the same depth is sufficient. 
 If the ground has been properly prepared, large holes, except in cases 
 of replants, are of no advantage. In fact, they are a disadvantage 
 for very often the tree will settle and be too deep. The most impor- 
 tant precaution in planting a tree is to get the soil well firmed around 
 the roots. The soil should be worked in around the roots and firmed 
 with the feet. The tree should be planted so that it will be at about 
 the same depth as it stood in the nursery. Do not plant the tree too 
 deep. 
 
 / 
 
ClRC. 284] THE AIjM OND IN CALIFORNIA 17 
 
 Cultivation. — The general methods of cultivation suitable for other 
 orchard fruits may be used with almonds. Some people have thought 
 that since the almond will withstand prolonged periods of drought, it 
 will thrive under careless cultural treatment. This, however, is not 
 the case. 
 
 A suitable method of soil handling would be somewhat as follows : 
 Plowing should be done in the spring. If cover crops are grown, 
 they should be allowed to grow high in order to provide large quan- 
 tities of humus. Care must be exercised, however, especially where 
 irrigation is not possible, to prevent the vegetation from exhausting 
 the moisture from the upper soil. The plowing should be done early 
 enough to be followed by one or more good rains. The depth of plow- 
 ing should be varied from year to year in order to prevent the forma- 
 tion of an impervious plow pan. After plowing, the ground should 
 be worked down, generally with a disc, before the plowed surface has 
 a chance to bake. The conditions and type of soil will determine 
 whether it will be necessary to harrow or possibly roll to firm the soil 
 and break up clods. ^ 
 
 Subsequent cultivations will be determined by weed growth and 
 type of weeds. Sufficiently frequent cultivations should be given to 
 keep down weed growth, and if morning-glory is present, it will be 
 necessary to use a weed cutter. By using a weed cutter once a week 
 throughout the season, the morning-glory may be practically eradi- 
 cated in one season. It is absolutely necessary in order to kill the 
 morning-glory plants, not to allow them to show above ground. It 
 should be remembered that weeds in an orchard, especially an unirri- 
 gated orchard, are detrimental, because they extract much moisture 
 from the soil. 
 
 Recent investigations indicate that very little moisture is lost 
 through direct evaporation from the soil surface under California 
 conditions. The greatest loss is from transpiration through the leaves 
 of the trees and weeds. 
 
 When the land has been plowed and brought to a good state of 
 tilth, little cultivation will be needed through the remainder of the 
 summer, except to kill weeds, and put the soil in good condition after 
 an irrigation. Excessive cultivation continued after the surface has 
 been put in good condition is probably a useless expense. 6 
 
 Cover Crops. 7 — Constant cultivation throughout the summer pro- 
 motes the destruction of the humus and, by hindering the growth of 
 
 s California Agr. Exp. Sta., Ann. Eept., 1922, p. 104. 
 
 7 For additional information on cover crops see California Agr. Exp. Sta. Cir. 
 255, 1922, and also California Agr. Exp. Sta. Cir. 257, 1923. 
 
18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 vegetation, prevents the addition of a natural supply of humus to 
 replace that which has been lost. 
 
 The plowing under of annual winter cover crops does not entirely 
 replace the humus burned out in the summer, but reduces the annual 
 net loss and at the same time improves the texture of the soil. 
 
 Melilotus indica (yellow sweet-clover) is one of the good orchard 
 cover crops. To secure satisfactory growth, it must be planted early 
 (September), a factor which practically prevents its use where irri- 
 gation water is not available. 
 
 Very often vetch (Vicia sativa) will make a good stand when late- 
 planted, though this is not always the case. 
 
 In some sections burr-clover is the best crop which can be used. 
 It often reseeds and comes up year after year, especially where fall 
 irrigation is practiced or in regions of early autumn rains. Where 
 no irrigation water is available, the safest crop is probably barley or 
 rye. A rather new but promising cover crop is the small-seeded horse 
 bean which generally grows well in the cold winter months. 
 
 In addition to the winter cover crops named above, alfalfa is being 
 successfully used by some growers as a permanent cover or shade 
 crop in old orchards where irrigation is practiced. Too many 
 growers, forgetting that the almond trees are their main crop, irrigate 
 and care for the alfalfa at the expense of their trees. 
 
 In some situations alfalfa in almond orchards increases the 
 humidity of the atmosphere sufficiently to aggravate the trouble with 
 shot-hole and brown rot. 
 
 The following quantities of seed to the acre should give good 
 results : Melilotus, 20-25 lbs. ; burr-clover, 20 lbs. ; vetch, 50 lbs. ; small 
 seeded horse bean, 35-45 lbs. ; barley or rye, 50 lbs. 
 
 Irrigation. — Almond growers are becoming more convinced that in 
 numerous orchards irrigation is advisable. This is especially true in 
 bearing orchards where there is a light rainfall. Trees in heavy bear- 
 ing require more water, necessitating the addition of irrigation to 
 supplement rainfall. Where irrigation is practiced judgment must 
 be used in the amount and frequency of application of water. While 
 definite directions cannot be given as to either, it is probably safe 
 under all conditions to give at least a light irrigation (about two 
 acre-inches) in the fall for seeding the cover crop and also for the 
 benefit of the buds. In early spring if it is found that the winter 
 rainfall has not wet the ground to a depth of six feet, the deficiency 
 should be made up by irrigation. Whether it will pay to irrigate in 
 summer has not been definitely determined, but keeping up the vigor 
 
ClRC. 284] THE almond IN CALIFORNIA 19 
 
 of the trees throughout the season would no doubt materially aid in 
 controlling the red spider. In dry years a large percentage of the 
 hulls fail to open, making hulling impossible. When the hulls begin 
 to split it is advisable to irrigate. This reduces the number of " stick- 
 tights. " 
 
 The above discussion applies to middle-aged and old trees. Young 
 trees, eight to ten years old, may do very well without any irrigation 
 whatever if the average rainfall is sixteen inches or more. 
 
 Numerous methods of applying water may be used. The check 
 and furrow systems are most generally employed. 8 
 
 Fertilization. — Little or no systematic work has been done up to 
 the present time in the use of commercial fertilizers on almonds. The 
 use of barnyard manure is desirable wherever obtainable. The value 
 of almond hulls as fertilizer is doubtful, because of the difficulty of 
 bringing about their thorough decay. Because of the high percentage 
 of tannin they contain, it is inadvisable to use more of them than 
 would naturally fall from the tree. The use of lime to correct soil 
 acidity and to improve the texture of heavy soils is desirable if the 
 cost is not prohibitive. 
 
 PRUNING^ 
 
 Pruning properly begins with the training of the young tree 
 the first summer in the orchard. At the time of planting the tree 
 is generally cut back to a whip about twenty-seven inches long. In 
 rare cases, when good nursery laterals occur where wanted, they 
 may be saved and shortened to eight or ten inches. As a rule, how- 
 ever, all the nursery laterals are cut off. The framework branches 
 must be grown from dormant buds or from adventitious buds which 
 arise around the wounds caused by removing the nursery laterals. In 
 the spring (April or May) much good work in training the framework 
 may be done by going over the trees carefully and selecting the 
 branches desired for the framework. At this time the growth is only 
 a few inches long, and the undesirable twigs are easily subdued by 
 pinching out their terminals. This will encourage the growth of those 
 selected for framework branches. These should be allowed to grow 
 untouched. The undesirable branches should not be removed entirely 
 because their leaves manufacture plant food and by shading help to 
 prevent sunburn of the trunk. 
 
 s For methods of applying water see U. S. Dept. of Agr. Farmers' Bull. 8S2, 
 1917. 
 
 o For additional data on priming see California Agr. Exp. Sta. Bull. 313, 1922, 
 and also California Agr. Exp. Sta. Bull. 386, 1925. 
 
20 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 If a tree is allowed to grow the first summer without this treat- 
 ment, three to five of the uppermost buds will develop into good strong 
 branches by the end of the growing season, while only short twigs 
 will develop from the buds lower down on the trunk. The latter can- 
 not be used as framework branches. In this case, it will be necessary 
 to select the three framework branches all arising from practically 
 the same point on the tree, a condition which in later years causes 
 crowding and the formation of water pockets (fig. 5). 
 
 Fig. 5. — The result of selecting branches arising from one point on a main 
 trunk. In this so-called water pocket note the entire blade of the knife is under 
 water. This photograph is of a ten-year-old almond tree. The trouble is only 
 just beginning, and unless immediate steps are taken for its remedy the usefulness 
 of the tree will be shortened many years. From Bull. 313, California Exp. Sta. 
 
 The best type of head is one in which the branches are spaced as 
 far apart as possible along the trunk. The ideal is to have three 
 branches (with more it is impossible to avoid crowding), spaced about 
 six inches apart and arranged spirally around the trunk, forming 
 equal angles of about 120 degrees. The only way to get strong 
 branches where they are desired is to pinch the tips of all badly 
 
CIRC. 284] THE ALMOND IN CALIFORNIA 21 
 
 placed shoots. This diverts the growth into those suitably placed. It 
 is advisable to go over the orchard again in June to subdue additional 
 undesirable growth. 
 
 Pruning One-year-old Trees. — The first winter's pruning may be 
 done at any time after the leaves fall, approximately one year after 
 planting. If summer pinching has been done, there will be very little 
 to do except to cut back the three scaffold branches to from fifteen to 
 thirty inches to a lateral if possible — according to the variety of 
 almond, and the growth the tree has made. 
 
 On account of its spreading habit of growth a Drake will have to 
 be headed more severely than an upright variety such as the Ne Plus 
 Ultra or I. X. L. In cases where trees have made a very vigorous 
 growth during the first summer in the orchard, it may be desirable 
 to head them when they have made a growth of fifteen to thirty 
 inches. A secondary branching may thus be secured during the first 
 summer. In this case the first winter's pruning will consist of a 
 thinning only, since a sufficient number of framework branches have 
 been secured (five-seven at about five feet from the ground). If the 
 trees have, for some reason, made very poor growth during the first 
 season, they should receive no pinching out in the summer and little 
 or no pruning in the first winter so that they may have as much leaf 
 surface as possible to build up the tree and make a strong healthy 
 growth the second season. 
 
 Figure 6 shows a Nonpareil almond, before pruning, after one 
 season's growth in the orchard. At the time of planting the nursery 
 laterals were saved and headed at "A." Figure 7 shows the same 
 tree as figure 6 after pruning. 
 
 Pruning During the Second Season. — When growth starts the 
 second spring, numerous sprouts will be produced around pruning 
 wounds and also from dormant buds where they are not wanted. It 
 is a good plan to go through the orchard in early May or whenever 
 these sprouts are eight to ten inches long and pull off or cut out those 
 not wanted and pinch back those which will make desirable fruit 
 spurs (the less vigorous ones). The removal at this time of undesir- 
 able branches which are likely to grow at the expense of the desirable 
 ■framework branches is also recommended. Since the almond makes 
 numerous lateral branches it is not usually necessary or even desir- 
 able to give any heading to the framework branches the second season. 
 
 If no spring pinching has been given during the second spring 
 and summer, it will be necessary to remove the watersprouts and ill- 
 placed branches. Occasionally, when a tree has made an unsym- 
 
22 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Fig. 6. — One-year-old Nonpareil before pruning. At the time of planting the 
 nursery laterals were saved and headed at "A. " 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 23 
 
 metrical growth, a watersprout may be used to advantage for a frame- 
 work branch if growing in the proper position to fill a vacancy. Gen- 
 erally no heading is necessary, especially if the tree has five to seven 
 branches and sufficient spread. 
 
 Fig. 7. — Same tree as fig. 
 laterals headed moderately. 
 
 6 after pruning. Thinned to laterals and the 
 
 Pruning the Third and Fourth Years. — If the trees have been 
 pruned as above outlined (it is assumed that soil, moisture, etc., are 
 favorable for good vigorous growth), the only pruning necessary will 
 
24 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 be a thinning out with no heading (fig. 8). These trees should 
 produce a considerable crop of nuts the fourth summer and should 
 thereafter be handled as bearing trees. 
 
 Pig. 8. — Nonpareil almond. Three years old. After pruning. Thinned only. 
 
 Pruning Bearing Trees. — If young almond trees have been prop- 
 erly trained and pruned, the bearing trees should not be hard to 
 prune. The commercial practice in almond pruning consists mainly 
 in the removal of watersprouts and branches averaging one-half inch 
 
Cmc. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 25 
 
 in diameter, no attention being given to the one-year-shoots (fig. 9). 
 Occasionally it will be necessary to remove a larger branch as it begins 
 to interfere or cause crowding. It is necessary to keep the trees open 
 so that the sun can filter down through the leaves and maintain a 
 healthy condition in the lower buds and fruit spurs — otherwise the 
 fruiting area will be confined to the outer area of the tree. This 
 practice also facilitates harvesting. Normally, bearing almond trees 
 are not expected to make more than from eight to fifteen inches of 
 
 w 1 
 
 
 \ :■/(/'/ 
 
 ,A * 
 
 Fig. 9. — Six-year-old Nonpareil. ' ' Moderately pruned. ' ' 
 
 new wood growth each year. If trees are making much more growth, 
 it may be advisable to cease pruning for several years. This is likely 
 to throw the trees into heavy production and thus slow down vegeta- 
 tive growth. After regular bearing is established, a moderate pruning 
 should be given to get the trees back into proper shape. On the other 
 hand, if they are making little or no growth, some of the fruiting 
 branches should be removed. This will invigorate the trees (fig. 10). 
 Very often, however, the lack of growth is due to soil moisture con- 
 ditions and cannot be materially influenced by pruning alone. 
 
26 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 KEJUVENATION OF OLD TKEES 
 
 Through one cause or another, old trees sometimes reach a con- 
 dition where production is so low that they are no longer profitable. 
 The question which confronts the grower is what to do with the trees 
 to get them back to profitable production. If the trees are sound, 
 that is, not affected with severe infections of crown gall or heart rot, 
 and not growing under adverse conditions such as shallow soil, under- 
 lying hardpan, or lack of moisture, they can very often be rejuvenated 
 by cultural treatment. 
 
 Fig. 10. — Twenty-seven-year old Ne Plus Ultra after having been severely 
 thinned. This tree had not been pruned for six or eight years. 
 
 Sometimes a thorough spraying to destroy the pests and the addi- 
 tion of irrigation is sufficient. Very often a more or less severe prun- 
 ing will be necessary. Generally this pruning should consist of the 
 removal of a considerable number of rather large branches. In order 
 to prevent sunburn, the thinning out and opening up of the trees 
 should be gradual. Frequently the removal of a larger number of 
 smaller branches all over the tree is more advisable than removing a 
 large limb here and there. 
 
 Under certain conditions it may be best to dehorn the trees about 
 six feet from the ground and form a new head from the suckers which 
 arise near the end of the stubs. This method is not always satis- 
 
ClRC. 284] THE ALMOND IN CALIFORNIA 27 
 
 factory, especially in windy sections. The new shoots do not have a 
 very strong union with the stubs and after they come into bearing 
 will, from time to time, blow off. 
 
 ORCHARD HEATING FOR FROST PREVENTION^ 
 
 On account of their early blossoming habit the almonds are fre- 
 quently injured by frost. Recently considerable interest has been 
 shown in methods of protecting them from this danger. The use of 
 orchard heaters in some districts has become a common and successful 
 practice. It is possible economically to control several degrees of 
 frost for three or four or possibly more nights by a judicious use of 
 heaters. 
 
 The best type of heater 10 for almond orchards has not been 
 thoroughly worked out as yet. Both the "lardpail" or open type and 
 the improved stack type of heater are being used. 
 
 At least seventy-five one or two-gallon lardpail heaters to the acre 
 are necessary to control temperatures as low as 27 or 28 degrees F. 
 Probably not over 100 pots to an acre would be needed at most. A 
 smaller number of the stack heaters are sufficient. Double the number 
 of pots should be placed around the outside especially on the wind- 
 ward side. 
 
 The gravity of oil best suited for orchard heating is between 20 
 and 25 degrees Baume. It is essential that it be as free as possible 
 from impurities such as sulfur. During the spring of 1917, orchard 
 heating was done very extensively in some districts of the state while 
 the trees were approaching full bloom. As the season progressed, it 
 became apparent that some serious injury had been done by the heat- 
 ing, for the bulk of the blossoms fell off and the leaves turned yellow in 
 streaks as if burned by an acid. It seemed as though the pistils of the 
 flowers and the young leaves had absorbed sulfur dioxide gas (a 
 product of oil combustion, where sulfur is contained in the oil), which 
 in uniting with the dews had formed sulfurous acid, which had done 
 the damage. Had the heating been done only after the trees had 
 passed full bloom, a much heavier set of nuts might have been secured, 
 since the small fruits, where they had formed, seemed to have been 
 uninjured, only the pistils of the flowers having been affected, prob- 
 ably preventing pollination and fertilization of the ovules. 
 
 The time of heating is therefore a very important point. Almond 
 blossoms become progressively more tender to frost as they advance 
 
 io Additional information may be obtained from the Almond Growers' Ex- 
 change Bulletin entitled, " Frost Protection— Orchard Heating," pp. 1-8, 1923. 
 
28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 in development. With their petals on, they are not nearly so tender 
 as they are after the petals have fallen. They reach their most tender 
 stage after the calyx shucks have fallen and before the fruits are the 
 size of a pea. Ordinarily, orchard heating before the trees have 
 passed full bloom is a waste of time and material and is often 
 injurious. The most necessary time for heating is usually during the 
 two or three weeks after the bulk of the petals have fallen, unless 
 temperatures below 28 to 29 degrees are encountered before that time. 
 The most complete treatise on orchard heating is U. S. D. A. Farmers' 
 Bulletin No. 1096, entitled " Frost and the Prevention of Damage 
 by It." 
 
 CEOP HANDLING 
 
 Harvesting. — The harvesting of the crop should begin as soon as 
 the hulls have opened to their fullest extent, and no time should be 
 lost in completing the work. The nuts in the center of the tree are 
 the last to ripen and so may be used as indicators. If harvesting is 
 begun too early, the nuts will cling to the tree rather tenaciously and 
 require very vigorous knocking to loosen them. On the other hand, 
 if they are allowed to hang too long after ripening, a number of 
 difficulties may be encountered. They may be blown to the ground 
 by light winds and the cost of gathering be increased, as quite com- 
 monly occurs with the Peerless ; or the hulls may dry up and in doing 
 so close around the nuts to a greater or less extent and add to the cost 
 and difficulty of hulling. This is most noticeable with the Nonpareil. 
 Strong winds will break off a great many of the nuts of any of the 
 varieties, and promptness is doubly essential where there is any like- 
 lihood of such winds occurring during the harvest season. Depreda- 
 tions by birds may cause serious losses, especially with the soft and 
 paper-shell varieties. Infestation by worms may often be quite 
 serious in the papershell varieties, when they are allowed to hang too 
 long. In case of damp or foggy weather, the shells turn dark and 
 sometimes commence to mildew, requiring heavier bleaching to 
 brighten them sufficiently for market demands. Rain stains can never 
 be removed entirely by ordinary bleaching. 
 
 The crop is harvested by knocking the ripened nuts and hulls with 
 long poles onto sheets spread on the ground under the trees. The 
 knocking should be done near the portions of the trees where the nuts 
 are borne and by striking a number of light, quick blows, rather than 
 by a heavy blow aimed to jar a large branch. This method avoids 
 injury to the bark by bruising and will accomplish the work in less 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 29 
 
 time. The blows should always be delivered squarely against the 
 branch. A glancing blow will tear the bark and break off a great 
 many fruit spurs, thus reducing the bearing surface for the next year. 
 For this reason harvesters must be watched closely all the time to 
 insure the proper use of the poles. The sheets, two in number, are 
 spread under the trees so they will overlap and catch all the nuts that 
 fall (see fig. 11). When sufficiently loaded with nuts to make 
 dragging the sheets from one tree to another difficult, they are 
 emptied into lug boxes or bags and sent to the huller. 
 
 Fig. 11. — Harvesting almonds by knocking onto sheets spread on ground. 
 
 The character of the harvesting equipment may vary consider- 
 ably, according to the acreage, character of trees and ground, time 
 required, capital available, and the ideas of the owner. Some growers 
 use heavy poles of pine, spruce, or fir, while others prefer the lighter 
 bamboo poles. The heavy poles are from 1% to 2 inches in diameter 
 at the base and from % to 1 inch in diameter at the top. Experience 
 has shown that poles of this type over 20 feet in length are unwieldy, 
 and not only swing slowly but do more damage because of the greater 
 difficulty of control. Most growers prefer 16-foot poles with a few 20- 
 
30 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 foot ones for use in the tops of the taller trees. Where the tops cannot 
 be reached with these, the men climb into the trees with shorter poles. 
 The bamboo poles used are about 24 feet long, and because of their 
 lightness, can be used with greater speed. Bamboo poles with short 
 internodes should be selected, as they are less likely to break. Break- 
 age may also be reduced by storing the poles in a cool place where 
 drying-out will not be excessive. 
 
 The sheets, which are made of 7 to 12-ounce duck, range in size 
 from 12 by 24 to 24 by 48 feet. They need not be much longer than 
 the longest diameter of the tree. To prevent mildew and rotting of 
 the fabric, the sheets should be boiled in a solution of tannin before 
 being used. Sheets thus treated last much longer. 
 
 Some growers have contrivances by which sheets are mounted on 
 sleds or wheels. The principal objection to such an arrangement 
 is that the sled or wheeled frame must be made in two sections, one 
 for each side of the tree, which increases the cost of the operation 
 because the horses can be used for nothing else while the harvesting 
 is in progress. On the other hand, when moved by dragging on the 
 ground, sheets will wear out in two or three seasons, while with the 
 sled or wagon method they will last from six to ten years longer. The 
 two wagons shown in figure 12, each 12 by 24 feet, cost between $60 
 and $70 about the year 1914. The canvas portion is of 8-ounce duck. 
 
 Fig. 12. — Portable almond sheets mounted on wheels as used by N. J. Lund, 
 Oakdale, California, 1916. 
 
CIRC. 284] THE ALMOND IN CALIFORNIA 31 
 
 By this method the knockers can gather ten lug boxes before empty- 
 ing. The work can be done much faster with wagons. When sleds 
 are used, one sheet is fastened lengthwise on the right side of the 
 left-hand sled and another on the left side of the right-hand sled. 
 More recently, single sleds have been devised with the two sheets 
 extending lengthwise on either side of the tree. The Division of 
 Agricultural Engineering of the University of California have avail- 
 able plans and specifications for such a sled. 
 
 Hulling. — After harvesting, the almonds, hulls and all, are taken 
 to the huller while still moist. If they become dry before hulling they 
 must be dipped in water or the shells will be broken. All hulling was 
 formerly done by hand, and this is still done where only small lots 
 are to be handled. The invention of machinery for this purpose has 
 reduced the cost of hulling from 60 to 80 per cent, for most outfits 
 separate the hulls from the nuts before they leave the machine. Some 
 of the hand hullers consist simply of the hulling portion of the large 
 power machine without the separating screens. These cost about 
 one-sixth or one-seventh as much as the large machines, and where 
 a man has a small acreage and is too far away to haul to a large 
 huller, a hand machine will greatly facilitate the work, even though 
 the final separation must be done by hand. 
 
 There are many different kinds of hulling and separating machines 
 now in operation in California, all invented by California almond 
 growers. The first one made was the Read " Sure-Pop'' almond 
 huller. This is now manufactured in three sizes by the Schmeiser 
 Manufacturing Company, Davis, California. The No. 3 huller, which 
 is generally best for orchards of less than ten acres, may or may not 
 be equipped with a separating device. If it has no separator, it may 
 be operated by hand; otherwise a small engine or motor is needed. 
 The No. 2 hullers both hull and separate and are operated only by 
 power. They should pay in orchards of ten acres or more. The 
 No. 1 is the largest made and is for use in orchards of 100 acres or 
 more. 
 
 The Beach huller is of more recent origin, having been in use only 
 since 1895. It was invented by J. E. Beach of Fairoaks, California, 
 and is being manufactured by him. Both sizes of this machine are 
 power outfits ; they are doing satisfactory work at the present time. 
 
 A third huller is that made by C. U. Reams of Suisun. More 
 recently, hullers have been invented and are being manufactured as 
 follows : 
 
32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 The Miller Huller, manufactured by L. L. Miller, Ripon, Cali- 
 fornia. 
 
 The Stephens Huller, manufactured by the Bean Spray Pump 
 Company, San Jose, California. 
 
 The Martinette Huller, manufactured by F. L. Martinette, Chico, 
 California. 
 
 The Vaughan Huller, manufactured by L. K. Vaughan, Wood- 
 land, California. 
 
 An unnamed huller, manufactured by Smith Manufacturing Com- 
 pany, San Jose, California. 
 
 The efficiency of these hullers depends largely upon the speed of 
 the machine and upon the condition of the almonds in the hulls. If 
 the machine runs too fast, the almonds are broken and injured, and 
 if it runs too slowly, many of the almonds are not hulled. If the 
 almonds are allowed to hang on the trees too long, the hulls become 
 dry and leathery, and the difficulty of hulling is greatly increased. 
 Dipping in water in such cases may help to overcome this difficulty 
 to a limited extent. 
 
 The papershell varieties, notably the Nonpareil, are much more 
 difficult to hull without breaking the shells than are the harder shelled 
 varieties. The Nonpareil hull has a tendency to close around the nut 
 on drying, making hulling very difficult. 
 
 Often when the moisture supply in the soil is exhausted before the 
 nuts are ripe, or when the loss of leaf surface due to mites is serious 
 before ripening, the hulls open only slightly or not at all, but dry 
 onto the shell of the nut. Such "stick-tights" can be disposed of 
 profitably only by allowing them to dry thoroughly, after which they 
 are cracked and sold as ' ' meats. ' ' 
 
 After the hulling operation, all almonds must be gone over by 
 hand to remove pieces of hulls and inferior or gummy nuts. Where 
 canvas drapers are not available for sorting directly from the huller, 
 the nuts are piled in hoppers and sorted on benches beneath them. 
 
 Drying. — Immediately after the sorting, the nuts are spread on 
 trays and thoroughly dried in the sun. In the interior valleys during 
 hot, dry weather the nuts will sometimes dry so quickly that by the 
 time the sorting from hoppers is completed, the nuts are sufficiently 
 dry. The grower must be certain, however, that such is the case 
 before the almonds are delivered to the warehouse. The nuts are 
 sufficiently dry when the kernels will break without bending. Quick 
 drying seems essential to prevent the excessive darkening of the shell. 
 
CIRC. 284] THE A L M OND IN CALIFORNIA 33 
 
 Bleaching. — The trade demands an almond with a bright golden- 
 yellow shell. In the earlier history of the almond industry, the 
 growers bleached their own almonds. As a consequence, there was no 
 uniformity in the product. At the present time the associations 
 advise that the almonds be delivered unbleached, as they have per- 
 fected machinery for bleaching and are thus able to produce a uni- 
 formly bleached product. 
 
 Their method in general consists of subjecting the almonds to a 
 low steam pressure for 10 to 20 minutes in order to moisten the shell. 
 They are then exposed to sulfur fumes for 10 to 30 minutes. One to 
 three pounds of the best grade of flowers of sulfur is necessary to 
 bleach one ton of almonds. Proper bleaching does not affect the 
 almond in any way. However, over-bleaching produces a sickly 
 yellow or whitish colored shell and also causes the kernel to deterior- 
 ate and become rancid. 
 
 Sacking. — During the preliminary handling of almonds, ordinary 
 grain sacks are commonly used. After bleaching, in which condition 
 they are ready for market, they are put in standard almond bags, 
 measuring 20 by 40 inches and weighing 1% pounds. The weight 
 of a bag of almonds varies not only with the variety but also with 
 the year and locality in which it is produced. For selling purposes 
 the California Almond Growers' Exchange estimates weights of differ- 
 ent varieties to be as follows : Nonpareil, 85 pounds to the bag ; I. X. 
 L., 80 pounds; Ne Plus Ultra, 75 pounds; Drake, 90 to 100 pounds; 
 Languedoc, 100 pounds; and hardshell almonds, 100 to 120 pounds. 
 The bags will be changed with the 1924 crop, and will measure 
 28 by 40 inches, and weigh, when filled, about as follows : Nonpareil, 
 I. X. L., and Ne Plus Ultra, 85-90 pounds; Drake, 100 pounds; Texas, 
 105-110 pounds; hardshells, 120-130 pounds. 
 
 Shelling. — The increasing popularity of shelled almonds, and the 
 limited market for unshelled ones during the past few years, have 
 made it imperative to give attention to methods of shelling. The 
 California Almond Growers' Exchange has perfected machinery 
 which together with increased tariff duties has enabled it to market 
 large quantities of shelled almonds during the 1923-24 season. Thus 
 there was but little carry-over into the 1924 crop season and none 
 into the 1925. A small proportion of the shelled almonds marketed — 
 usually not more than thirty pounds to the ton — are accidentally 
 shelled during the hulling process. 
 
 Recently a large proportion of the Texas variety has been shelled 
 and sold successfully. 
 
34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Papershells, however, are the varieties most commonly marketed 
 in this way, for two reasons : (1) their kernels do not break so readily 
 in the shelling process, and (2) the percentage of kernel is much 
 higher than in the harder shelled varieties. 
 
 Grading. — Though grading almonds for size is not practiced at 
 present, it probably will be within the next few years. Grading for 
 quality, however, is done regularly by testing an entire lot rather 
 than by attempting to separate inferior nuts. All lots free from 
 worms or gummy nuts and having a required percentage of good 
 kernels — 90 to 95 per cent, according to the conditions of the market 
 and of the crop as a whole — are considered standard grades, and are 
 sold on guarantee. All lots which cannot pass this test are sold on 
 sample, and therefore, on their own individual merits. 
 
 MARKETING 
 
 Exchange Organization. — The marketing of the almond crop of 
 California is at present on a firmer basis than at any time in the past. 
 Before 1910 there was little or no cooperation among growers, and 
 the buyers had everything their own way. In May of that year, how- 
 ever, Mr. J. P. Dargitz, an almond grower near Acampo, California, 
 successfully organized the California Almond Growers' Exchange, 
 consisting of nine local sub-associations, with a total membership of 
 230 growers. The Exchange started business with $1000, borrowed 
 capital, personally guaranteed by the directors. On June 1, 1918, 
 there were twenty-two sub-associations representing about 2000 grow- 
 ers, and controlling about three-fourths of the crop. On April 1, 
 1924, the association had a membership of 3359, controlling 70 per 
 cent of the crop. All members are on a five-year contract basis. The 
 Exchange now is not only out of debt but has assets of about $400,000, 
 including warehouses, a central shelling plant, and other property. 
 At the same time, the growers have been receiving about 50 per cent 
 more for their almonds then before the Exchange was organized. 
 
 The success of the Exchange, with the consequent higher prices 
 to the grower, has resulted in a large increase in the acreage of 
 almonds in California. This increase is making it necessary to 
 develop new markets to absorb the consequent greater tonnage, which 
 can be done satisfactorily only by cooperative effort. 
 
 Until 1923, California almonds were marketed chiefly in the shell, 
 though a small quantity had been cracked annually to supply west- 
 
ClRC. 284] THE ALMOND IN CALIFORNIA 35 
 
 ern brokers and confectioners. Virtually all of these were sold west 
 of the Rocky Mountains. During the 1923 crop season, however, the 
 Exchange sold over 1,300,000 pounds of shelled almonds. 
 
 European Competition. — European growers who send their crops 
 to the United States largely as "meats" had practically a monopoly 
 of the shelled almond business until 1923. The unshelled Tarragonas, 
 Princess, etc., shipped to America come into direct competition with 
 the I. X. L., Drake, Languedoc, and other California almonds, all of 
 which are unshelled. The amount of unshelled almonds imported is 
 about equal to the California production. The Jordan, Valencias, 
 and other varieties constituting the bulk of the importations, how- 
 ever, come shelled. The Jordan, because of its superior quality, is 
 almost in a class by itself and does not at present cause serious com- 
 petition with the California product. The Princess and other almonds 
 of the same type are very similar to the California shelling varieties 
 and are serious competitors when offered in the same markets. 11 
 
 Storing. — Almonds become rancid if stored in warm or damp 
 places. If they have been properly cared for during the handling 
 process to prevent worm infection, and have been thoroughly cured, 
 however, they will keep satisfactorily in suitable storage for a year or 
 more while awaiting removal or sale. The places where they are 
 stored should be uniformly cool, dry and with ample ventilation. 
 
 COST OF PBODUCTION 
 
 The amount and kind of equipment of the average almond orchard 
 is extremely variable. The larger and more progressive orchards are 
 usually w T ell equipped with all the necessary tools and power. Many 
 small growers, however, can not afford all the machinery necessary 
 for running their places. Most orchardists have their own tillage 
 and harvesting equipment, though some prefer to depend upon their 
 neighbors to do their hulling by contract. 
 
 In addition to the ordinary orchard equipment, the almond grower 
 needs special equipment for harvesting, hulling, and drying. This 
 includes canvas sheets, poles for knocking, lug boxes or sacks, a huller, 
 sorting tables or bins, trays, and sacks for delivery to the warehouse. 
 Sheets cost from $20 to $100 according to the size and quality ; poles 
 15 cents or more; lug boxes 35 cents; hullers $150 to $1200; trays 
 
 ii The increasing popularity of shelled almonds makes it advisable that the 
 American markets be made familiar with the California shelled product, and that 
 its sale be extended as quickly as possible. This is indeed necessary because it has 
 been found impossible to dispose of the whole of the present annual production 
 in the shell, and the prospects are for a greater production in the near future. 
 
36 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 about 75 cents; sacks about 15 cents; sorting tables or bins are gen- 
 erally made by the grower at the cost of material and making. 
 
 The average cost of harvesting (knocking, gathering, and deliver- 
 ing to the huller) is about three cents a pound, and the cost of hulling 
 and drying about two cents a pound. The harvesting costs vary 
 greatly, largely according to the size of the crop. The smaller the 
 crop the greater the proportionate cost. 
 
 The cost of orchard operations varies with the prevailing wages. 
 Cultivation, including plowing, probably costs $15 an acre; spraying 
 about $10 an acre; pruning and burning brush, about $7; and irri- 
 gating, if practiced, about $8 an acre. 
 
 To these costs must be added taxes, insurance, upkeep of tools, 
 depreciation on equipment and buildings, cost of feed, and interest 
 on the investment. 
 
 Yields. — The yield of almonds in different years and in different 
 orchards is probably more variable than that of any other of the 
 common orchard fruits. While the fluctuations from year to year 
 are largely due to climatic conditions, the variations in orchards are 
 due largely to variety, care given the trees, character of soil, and frost 
 conditions. 
 
 Almonds begin bearing at from two to four years, the first crop 
 ranging from one or two nuts up to a hatful, or possibly more. At 
 three to five years, they should yield a crop which will pay for har- 
 vesting. Ordinarily, the first crop that it will pay to harvest is not 
 obtained until near the latter age, though this depends upon the type 
 of soil in which the trees are growing and the moisture conditions 
 surrounding them. On the hill lands the trees begin to mature much 
 earlier than in the rich bottom lands, and consequently come into 
 bearing earlier. It must be borne in mind that a crop which it will 
 pay to harvest does not necessarily mean a paying crop. It does not 
 become a "paying crop" until it covers the cost of maintenance as 
 well as of harvesting and handling. Almond orchards, as a rule, 
 reach this point in from five to seven years. From this time the trees 
 should continue to increase in production from year to year, allowing 
 for failures due to frost and unfavorable conditions, until they are 
 from twelve to twenty years old. Under the common methods of care 
 that most orchards receive, the trees begin decreasing in production 
 after twenty-five to thirty years, and in some cases earlier. On the 
 other hand, orchards that are well cared-for often continue their 
 maximum production even longer. The age at which an orchard will 
 not longer pay ranges from thirty years upward. The limit is still 
 unknown. 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 37 
 
 Investigations carried on during 1913-1 4 12 brought out the follow- 
 ing facts : The average production of almonds in California is between 
 700 and 800 pounds per acre ; if care is exercised in the selection of 
 a proper location for an orchard and if good judgment is used in 
 managing it, 1000 pounds per acre would be a safe estimate for 
 business purposes; in many years competent orchardists may expect 
 to obtain 1500 pounds per acre, but this would not be likely for a 
 ten-year average. The possibilities are indicated by the crop from 
 one acre, on the University Farm at Davis, California, of ten-year-old 
 trees which produced nearly 2800 pounds in 1917. 
 
 TABLE 3 
 
 Net Prices (in Cents per Pound) Realized by the Exchange Members for 
 
 Different Varieties for the Years 1910 to 1923, Inclusive 
 
 Year 
 
 Nonpareil 
 
 I. X. L. 
 
 Ne Plus Ultra 
 
 Drake 
 
 1910 
 
 14.00 
 16.50 
 13.25 
 17.25 
 18.00 
 13.00 
 17.25 
 17.50 
 24.00 
 26.00 
 18.50 
 18.00 
 20.00 
 15.00 
 
 13.00 
 15.50 
 12.25 
 16.25 
 15.00 
 12.00 
 14.75 
 16.00 
 22.00 
 24.00 
 18.50 
 17.00 
 18.00 
 13.00 
 
 12.00 
 14.50 
 
 11.25 
 15.25 
 14.50 
 11.00 
 13.75 
 15.00 
 21.00 
 21.00 
 16.50 
 16.00 
 16.00 
 13.00 
 
 10.00 
 
 1911 
 
 12.00 
 
 1912 
 
 9.50 
 
 1913 
 
 13.25 
 
 1914 
 
 11.50 
 
 1915 
 
 9.25 
 
 1916 
 
 13.00 
 
 1917 
 
 12.50 
 
 1918 
 
 17.00 
 
 1919 
 
 14.00 
 
 1920 
 
 9.00 
 
 1921 
 
 9.00 
 
 1922 
 
 11.00 
 
 1923 , 
 
 8.00 
 
 
 
 Average 
 
 17.73 
 
 16.23 
 
 15.05 
 
 11.36 
 
 
 
 Returns. — Prices paid to growers have fluctuated considerably on 
 account of the great variation in both the Californian and European 
 crops from year to year. Table 3 shows the average price paid to the 
 growers for the four principal varieties marketed through the Almond 
 Growers' Exchange since its organization. 
 
 Table 4 shows the average price per pound paid to the growers 
 for all almonds (unshelled), including all qualities and the entire crop 
 handled by the Exchange during the years 1910 to 1923 inclusive. 
 
 From these figures it has been found that the average return per 
 pound for all varieties for fourteen years based on the crop tonnage 
 
 12 California Agr. Exp. Sta., Cir. 121, 1914. 
 
38 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 for each year, 1910 to 1923, inclusive, was 13.98 cents. It is interest- 
 ing to note that the 1923 crop is the largest produced in the state and 
 also that the average price paid growers is practically three cents less 
 than the average for the fourteen years. 
 
 TABLE 4 
 
 Average Prices per Pound Paid Growers for all Unshelled Almonds for the 
 Years 1910 to 1923, Inclusive 
 
 Year 
 
 Price per Pound, 
 
 Cents 
 
 California Crop, 
 Tons 
 
 1910 
 
 12.00 
 13.50 
 11.00 
 15.50 
 14.05 
 10.75 
 13.97 
 14.23 
 19.81 
 19.01 
 13.48 
 13.40 
 14.06 
 10.98* 
 
 3,300 
 
 1911... 
 
 1,450 
 
 1912 
 
 3,000 
 1,100 
 2,250 
 
 1913 , 
 
 1914 
 
 1915... 
 
 3,500 
 3,400 
 
 1916 
 
 1917 
 
 4,000 
 
 1918 
 
 5,100 
 
 1919 .. 
 
 7,250 
 
 1920 
 
 5,500 
 
 1921 
 
 5,500 
 
 1922 
 
 8,500 
 
 1923 
 
 11,000 
 
 
 
 
 Average . 
 
 13.98 
 
 4,632 
 
 
 
 Estimated. 
 
 ALMOND DISEASES AND PESTS AND THEIR CONTROL 
 
 DISEASES 
 
 Crown-Gall. — This disease, which is also known as root-knot or 
 black-knot, is one of the most serious with which the grower has to 
 contend. It is found practically everywhere that almonds are grown, 
 and either greatly reduces the vitality of the trees affected, or kills 
 them, according to the seriousness of the attack. The name "root- 
 knot" is more commonly applied to root swellings caused by nema- 
 todes. 
 
 Crown-gall is caused by a bacterial organism, Bacterium tume- 
 faciens S. & T., that seems to be native to most California soils. It 
 is characterized by large swellings on the root crown or main roots 
 just below the surface of the ground, though milder infections may 
 sometimes be found also on the smaller roots. When cut open, the 
 
CIRC. 284] THE ALMOND IN CALIFORNIA 39 
 
 knots appear spongy as if the bark and wood were mixed together in 
 one mass. They are most serious when spread over a large surface, 
 either partially or completely girdling the root or crown of the tree. 
 Control methods are of two kinds : 
 
 (1) Nothing but clean, healthy nursery trees, free from all trace 
 of galls, should be planted. All broken or injured roots should be 
 carefully trimmed off, leaving nothing but smooth, clean cut ends 
 which will heal over readily with the minimum opportunity for infec- 
 tion. 
 
 (2) Galls on orchard trees may be cut out to clean, healthy wood 
 with a sharp knife or gouge chisel. The wound should be thoroughly 
 disinfected with a strong (5 to 10 per cent) copper-sulfate solution 
 or a mixture of corrosive sublimate and mercury cyanide, 1 part of 
 each to 500 parts of water by weight, and painted when the surface 
 is dry with a protective covering such as a lead and oil paint or 
 melted asphaltum, or it may be covered directly with Bordeaux paste. 
 The earth should be replaced over the roots. The trees must be 
 reinspected carefully and any new galls which have formed at the 
 wound margin removed and the new cuts disinfected. 
 
 The use of resistant stocks has been suggested as a means of avoid- 
 ing infection, but no such stock suitable for the almond has yet proved 
 to be sufficiently resistant under average conditions to be safely recom- 
 mended. The greatest hopes for future success in combating this 
 disease, however, lie in this direction. 
 
 Oak Fungus. — This is one of the most difficult diseases to control 
 because it works and spreads beneath the surface of the ground in 
 the roots of trees. In some sections of the state it is very serious. 
 
 The disease, often called root-rot, is caused by a fungus, Ar miliaria 
 mellea, commonly called "toadstool" fungus. It is known as oak 
 fungus because the disease is most commonly found on land where old 
 oak trees have stood. Where orchards have been planted on such 
 land, spots appear in which the trees gradually die, the disease spread- 
 ing from tree to tree, in ever-widening circles which take in ordinarily 
 about one row of trees each year. During the winter, clusters of 
 toadstools may be seen at the base of the affected trees. The fungus 
 lives over in the old oak roots for many years and, as the orchard 
 becomes well established, spreads to the almond roots. If not checked, 
 the spot will eventually involve the entire orchard and prevent 
 further growth of almonds on the land for many years. 
 
 The only remedy known is to construct barriers around diseased 
 spots, and thus prevent the infection from passing beyond through 
 
40 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 the roots. The spread of the disease may sometimes be held in cheek 
 by grubbing out a row or two of healthy trees outside the affected 
 area and taking care that all of the large roots are removed to a depth 
 of several feet. 
 
 There are no resistant stocks known at present upon which the 
 almond can be worked, but the fig, pear on French stock, and walnut 
 on Northern California Black Walnut stock may safely replace the 
 almond in affected spots. 
 
 Shot-hole Disease. — There are three different fungi that produce 
 the shot-hole effect on the leaves of the almond. 
 
 (1) Coryneum beijerinckii Oud, or peach blight, is the most com- 
 mon form. It is not so serious on the wood of the almond as it is on 
 that of the peach, but in seasons of damp spring weather it does 
 much damage to the blossoms, fruits, and leaves. Affected blossoms 
 are killed outright, the flowers turning brown and dropping much 
 as if killed by frost. The young fruit is spotted by the fungus, which 
 causes malformation, gumming, and shriveling of the nuts, varying 
 with the severity of the attack. On the leaves many small dead spots 
 appear, the dead tissue soon falling out and giving the shot-hole effect. 
 Where the twigs are affected, small dead spots appear during the 
 the winter, most often at the buds. This causes the death of the buds 
 and often the ends of the twigs, During the spring, after growth 
 starts, gumming occurs at these spots. 
 
 Only two sprays are known to give effective control — Bordeaux 
 mixture and lime-sulphur (winter strength). One or the other should 
 be given in the fall, as soon as the trees become dormant, and again 
 just before the buds open in the spring. Both the fall and the spring 
 sprays must be thoroughly applied to be effective. 
 
 (2) Cercospora circumscissa Sacc. is another fungus causing 
 much the same effect as the Coryneum. It is difficult for an un- 
 trained person to distinguish between them. The same sprays used 
 for Coryneum are effective in controlling the 'cercospora, though if 
 this form alone is present the spring spraying alone should be 
 sufficient. 
 
 (3) Gloeosporium amygdalinum Brizi, while apparently uncom- 
 mon in this state, has been found to exist in some places. Its behavior 
 and the most satisfactory methods of control are not exactly known, 
 but it is believed that the control measures mentioned for the other 
 forms of ''shot-hole" are also applicable to this. 
 
 Brown Rot (Sclerotina cinerea Wor.) is a fungous disease which 
 attacks all stone fruits including almonds. The flowers are susceptible 
 
CIRC. 284] THE ALMOND IN CALIFORNIA 41 
 
 when the petals show in the buds and remain so until the "jackets" 
 (calyx and other flower parts) are shed from the fruit. The fungus 
 grows down through the fruit into the twig. The inner bark turns 
 brown, and copious amber gumming generally occurs. Long shoots 
 may thus be killed by girdling. The fungus remains alive in the dead 
 twigs which serve as a source of infection the following spring. The 
 disease is rarely serious except near the coast and then only in seasons 
 when wet weather comes at the critical time. 
 
 During the fall all dead twigs should be cut out and destroyed. 
 Where the disease is serious, a Bordeaux 8-8-50 or a lime-sulfur 1-10 
 spray should be applied during the bud stage as the petals are show- 
 ing. (Lime-sulfur is preferable, especially when the twig borer and 
 almond mite eggs are present.) 
 
 Prune Bust (Puccinia Pruni Pers.). — This fungus is worst in the 
 southern coast sections where almonds are not extensively grown. 
 It is not serious on thrifty trees well supplied with moisture. It is 
 characterized by reddish pustules on the under sides of the leaves, 
 appearing generally about July or August and causing a premature 
 yellowing and dropping of the leaves. No method of control is 
 known. 
 
 Heart Rot. — This is one of the most insidious of tree diseases, for 
 it works inside beneath an apparently healthy exterior until the decay 
 has progressed so far that the tree commences to break down, and 
 then it is too late for remedial measures. The almond is not so 
 susceptible to this as most other kinds of orchard trees, but where 
 large wounds have been exposed to the weather, infection may take 
 place readily ; and after it is once well started, it continues at a com- 
 paratively rapid rate. Decay is caused in most cases by one or more 
 of about a dozen different fungi, of which the oyster-shell fungus is 
 by far the most common. 
 
 Control consists in taking care to leave no open wounds exposed 
 to the air to dry and crack and thus permit the entrance of decay 
 organisms. Much of this can be avoided by care in pruning the young 
 tree so that the removal of the large limbs will not be necessary later 
 on. Where such wounds must be made, measures should be taken 
 to prevent infection. This can be done best by making smooth, clean 
 cuts close to the part from which the branch arises. Such cuts heal 
 over more quickly than stubs which dry and crack and sometimes do 
 not heal over at all. All such wounds which do not heal over the 
 first season should be covered with some good disinfectant, such as 
 corrosive sublimate, 1 part to 1000 parts of water, or Bordeaux paste. 
 
42 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 When well dried the wound should be painted over with some elastic 
 coating, such as "Flotine," grade D asphaltum, or a good white lead 
 paint applied with a brush. The entire wound must be covered or 
 the work is largely wasted. 
 
 Die-back. — This is often serious in orchards where the moisture 
 is insufficient to carry the trees through the growing season. Unfavor- 
 able soil conditions, such as hardpan, gravel or sand, may be the 
 direct cause of such moisture shortage. Lack of soil fertility is also 
 a common cause. Control measures consist in remedying the defective 
 conditions. Where this cannot be done economically, it is better to 
 abandon further attempts at almond culture on such land. 
 
 Sour-sap. — This is one of the so-called "physiological diseases " 
 and is quite common in the almond. It is most frequently found 
 where trees are planted in heavy or poorly drained soils. The fact 
 that the almond cannot endure standing water around its roots for 
 any length of time, particularly after growth commences in the spring, 
 renders it especially liable to soursap in soils where excess water from 
 the late winter and spring rains cannot be readily drained away. 
 Sudden changes in weather from warm to cold after growth com- 
 mences are the direct cause of the trouble. The flow of sap is checked 
 very suddenly and stagnation, cracking of the bark, and fermentation 
 ensue. With an unusually strong flow of sap in trees in wet soils, 
 such climatic changes cause unusually severe disturbance in the 
 normal functioning of the trees. 
 
 The affected trees ordinarily show the disease first in the spring, 
 when gum may be seen oozing from the bark of the trunk or main 
 branches, and sometimes even from the smaller ones. Small or large 
 branches, and in severe cases, the whole tree, may die soon after begin- 
 ning to leaf out strongly. When the bark is cut through to the wood 
 and peeled back a strong sour odor is noticeable. The cambium 
 layer appears brownish or reddish in color, and often masses of gum 
 are found between the bark and the wood. Mild cases may not be 
 serious enough to show on the outside of the tree and only portions 
 of the cambium layer may die. The sudden dropping of the blossoms 
 or young fruit may in some instances be attributable to sour-sap. 
 
 All affected parts on smaller branches should be cut back to 
 healthy wood, while on the main branches or trunk, where only a 
 small portion or one side is affected, it is best to clean out the dead 
 bark and paint the bared wood with a protective covering until new 
 bark can cover the spot. At the same time, every effort should be 
 made to remedy the soil moisture conditions which were largely 
 responsible for the trouble in the first place. 
 
CIRC. 284] T H E ALMOND IN CALIFORNIA 43 
 
 Fruit-drop. — The same conditions which cause sour-sap may cause 
 fruit drop. Lack of pollination due to improper mixing of varieties 
 or to rain during the blossoming may be another cause. Frost may 
 also produce the same thing by killing the germ in the young fruit. 
 In such cases, the fruit may not fall from the tree for one or two 
 weeks after the injury occurs, and in some instances, may even appear 
 to continue its development for a short while. 
 
 INSECT PESTS 
 
 Mites. — Commonly called red spiders. 13 There are three kinds of 
 mites that do much damage in almond orchards, the brown or almond 
 mite, the common red spider or two-spotted mite, and the European 
 red mite. 14 These are common in all parts of the state and the first 
 two are the worst pests the almond grower has to face. 
 
 The brown mite (Bryobia praetiosa Koch), which does not spin 
 a web, is dark red or brown in the adult stage, has very long front 
 legs, and a flattened back. It works on the green bark of the small 
 twigs as well as on the leaves, sucking the plant juices from beneath 
 the bark. The leaves become mottled and eventually fall, although 
 not to such an extent as when attacked by the two-spotted mite. The 
 injury to the tree is just as great because of the serious drain on its 
 vitality and because of the earliness of the attack, most of the injury 
 being done in the spring and early summer. This mite may spend its 
 entire life on the tree ; the very small, round, red eggs being laid most 
 often on the under-side of the branches and in cracks and crevices 
 in the bark and twigs. These remain on the tree throughout the 
 winter and hatch early in the spring soon after the trees have their 
 leaves half developed, leaving the white egg-shells in place. 
 
 The brown mite may be controlled satisfactorily in the egg stage 
 by means of a dormant spray of lime-sulfur solution, one gallon to 
 nine gallons of water, applied just before the buds open in the spring. 
 Crude oil emulsion as a dormant spray is also effective, if thoroughly 
 applied over the entire tree under high pressure. The lime-sulfur 
 spray should be used in the same way. 
 
 During the growing season a milder material must be used. Dry 
 dust sulfur, using only the very finest grade of ''flowers of sulfur," 
 is often very effective, provided weather conditions are satisfactory. 
 It must generally be applied several times, however, if the best results 
 
 13 See also California Agr. Exp. Sta., Bull. 347, 1922. 
 
 14 Formerly called the citrus mite. 
 
44 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 are to be obtained. The work is done by blowing the sulfur dust into 
 the tree with blowers in the early morning when there is little or no 
 wind. 
 
 A more satisfactory method is to use 5 pounds of sulfur, % pound 
 of casein spreader, and 2 gallons of liquid lime-sulfur to 100 gallons 
 of water in cases where no winter treatment has been used, or where 
 there are no serious attacks of either of the other two species of red 
 spiders. 
 
 The common red spider or two-spotted mite (Tetranychus telarius 
 Linn) is of a pale yellow color with occasionally a reddish tinge and 
 sometimes two darker spots on either side of the body. It is a web- 
 spinning species. Unlike the brown mite, it spends the winter and 
 early spring on weeds and hardy cultivated plants. During the warm 
 days of early summer, generally in June, the mite makes its appear- 
 ance on the trees, spinning a fine web on the leaves, generally on the 
 upper surface, and then working under this web. The mite sucks the 
 plant juices from the leaves, giving them a yellowish mottled appear- 
 ance. These leaves soon die and drop to the ground. In serious 
 infestations the trees are often almost completely defoliated by the 
 end of August (see fig. 13). 
 
 The use of dormant sprays is not effective for controlling the 
 yellow mite, but the summer sprays mentioned above are all satis- 
 factory, and for the best results must be applied under high pressure, 
 preferably 200 pounds or more. 
 
 The citrus mite (Paratetranychus pilosus Can & Tanz) spins a 
 web, but is generally less abundant on almonds than either the brown 
 or the two-spotted mite. The life-history of this mite is similar to 
 that of the brown mite in that the winter is spent in the egg stage 
 on the host of the previous summer. 
 
 This mite is of a deep red color and is much smaller than the 
 almond mite. It is almost too small to be seen with the unaided eye. 
 The sprays mentioned above will control the citrus mite. 
 
 Peach Twig Borer 15 (Anarsia lineatella Zeller). — In the larval 
 stage these borers work on the young buds, shoots, and fruits. In the 
 early spring they are especially troublesome in newly planted orchard 
 trees when a comparatively small number may kill most of the new 
 shoots which are needed to make the desired framework of the tree. 
 In some years they may be serious in large trees also. Dormant spray 
 of lime-sulfur, 1-10, applied under high pressure just as the buds are 
 opening in the spring will generally control the borers. However, in 
 
 is See also California Agr. Exp. Sta., Bull. 355, 1923. 
 
CIRC 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 45 
 
 Fig. 13. — Nonpareil almonds. Branch on left free from Red Spider and 
 holding its full supply of leaves in green, healthy condition; branch on right 
 defoliated by Two-spotted mite. Note premature ripening of nuts on defoliated 
 branch. 
 
46 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 serious infections the addition of three pounds of basic arsenate of 
 lead to every 100 gallons of spray is advisable. This same spray may 
 be used to control the brown mite, thereby accomplishing double 
 control. 
 
 California Peach Borer (Aegeria opalescens Hy. Edw.). — The 
 larvae are serious in many parts of the state where they burrow just 
 under the bark near the surface of the ground. They may be detected 
 by the small bits of frass and gum at the entrance to their burrows. 
 If allowed to continue, they will eventually girdle the tree. 
 
 The surest means of control is to dig out the worms with a knife 
 or to kill them with a wire probe. This work should be done system- 
 atically in the fall and spring and the wounds painted with a good 
 asphalt paint. Use para-clichlorobenzine in summer and fall. 16 
 
 Thrips (Taeniothrips inconsequens Uzel.). — These are most serious 
 on the almond leaves, their attacks sometimes causing considerable 
 defoliation in late spring or early summer. They may be controlled 
 by spraying with distillate, to which has been added ' ' Black Leaf 40 ' ' 
 (40 per cent nicotine) at the rate of 1 part to 1500 parts of water or 
 other spray mixtures. It is possible that some insects other than the 
 pear thrips do similar damage, but the spray described above should 
 be effective against all. 
 
 Scale, aphis, diabrotica, and other insects are sometimes found on 
 the trees, but are generally not sufficiently troublesome to require 
 special attention. Most of them are held in check by the control 
 measures used for the more serious pests. 
 
 Indian Meal Moth (Plodia inter punctella Hln.). — The larva of 
 this moth feeds on the kernels of the harvested almonds after they 
 are stored. Infestation usually takes place in storerooms or ware- 
 houses in which the nuts have been placed for a time. The ware- 
 houses become infested from old grain bags which have been kept 
 there previously. So far as known, infestation does not take place in 
 the field. The larvae continue to work in the stored almonds for a 
 long time, doing a great amount of damage. They may be controlled 
 by thoroughly cleaning out the corners of the warehouse and 
 thoroughly disinfecting. The nuts should be disinfected with carbon 
 bisulphide (explosive when in the form of a gas mixed with air), or 
 by other means used to control insects in grain. Prevention is far 
 easier than cure in this case. 
 
 16 See also California Agr. Exp. Sta. Cir. 265, 1923. 
 
CIRC. 284] THE ALM0ND IN CALIFORNIA 47 
 
 SPEAY PEOGEAM 
 
 Under most conditions the following spray program is recom- 
 mended : 
 
 First Application. 
 
 In late winter before the buds open, with commercial lime-sulfur, 
 winter strength, for almond shot-hole fungus, brown mite (red spider) 
 eggs, moss and lichens and soft-bodied insects. Crude oil emulsion is 
 more effective against red spider eggs than is lime-sulfur solution. 
 
 Second Application. 
 
 In summer when two-spotted mite (red spider) appears, about 
 June 1 : 
 
 Flowers of sulphur — 5 pounds. 
 
 Casein spreader — % pound. 
 
 Liquid lime-sulfur — 2 gallons. 
 
 Water to make — 100 gallons. 
 
 Spray early, before red spider become numerous and as often as 
 necessary. 
 
 Additions or Modifications. 
 
 In certain sections where shot-hole fungus is serious a fall appli- 
 cation of Bordeaux mixture is recommended. 
 
 Where the peach twig borer is serious it is advisable to delay the 
 late winter lime-sulfur spray and add 3 pounds of basic arsenate of 
 lead powder per 100 gallons of solution. 
 
 OTHEE PESTS 
 
 Grasshoppers. — Grasshoppers have been serious in orchards in 
 outlying foothill districts in some years, and especially in young 
 orchards, making it almost impossible to get trees started properly. 
 In such locations special means must be employed on a large scale to 
 protect orchards from their devastations. Of these poisoned bait and 
 hopper dozers are the most effective. 
 
 Gophers. — These often do great damage to the trees by girdling 
 just below the surface of the ground. Even if they do not actually 
 girdle the trees, the injury may be sufficient to devitalize the tree ; 
 in addition, the wounds made by their gnawings frequently become 
 infected with crown-gall. The only safe means of control known is 
 the constant use of traps supplemented by poisoned bait. 
 
48 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Squirrels. — Squirrels are very troublesome, as they harvest a large 
 amount of almonds before they are sufficiently ripe to be harvested by 
 the grower. The use of poisoned grain or "gas," if used over a 
 large area of surrounding territory, will prevent serious depredations. 
 
 Birds. — Birds also carry off large amounts of almonds if the 
 orchards are near open country or hills, especially if wooded. Crows, 
 bluejays, blackbirds, yellow-hammers, robins, and others are the 
 worst offenders. Sometimes linnets eat off large numbers of fruit- 
 buds in the spring in some of the newer sections where plantings are 
 scattered. Sap-suckers have been known to girdle entire trees or 
 large branches by boring holes around the trunk or limbs. Generally 
 the damage from birds does not warrant any control measures. 
 
 Morning -Glory. — This is probably the worst of the weeds of 
 almond orchards, and is the hardest to control. Sheep and chickens 
 may be used with excellent results, provided care is taken to see that 
 the sheep are not allowed to go hungry, for then they will bark the 
 trunks of the trees very quickly. An excellent plan is to arrange 
 gates so that the sheep must go through the orchard from pasture to 
 get water. In passing back and forth they will forage over the entire 
 orchard and dig up all the morning-glory in sight. Chickens are 
 fond of the succulent new shoots, and will keep them below the ground 
 until the underground stems and roots weaken and die. Cultivation 
 throughout the growing season, often enough to prevent the morning- 
 glory from developing any leaves for a whole year at least, and longer 
 if necessary, will starve the plants to death. 
 
 VARIETIES 17 
 
 In selecting varieties of almonds for planting in California the 
 grower should choose those that are most marketable and that at the 
 same time secure the best results in cross-pollination. At the present 
 time there are comparatively few varieties of almonds which have 
 won and retained their popularity with both the grower and the 
 trade. There are a number of reasons for this condition. The cul- 
 tural, climatic, and soil conditions under which the almond thrives 
 are much more limited than for most of the common deciduous fruits ; 
 the area of production in America is limited largely to California ; the 
 industry is comparatively new, and in general, there is not the great 
 
 17 Detailed description of varieties may be found in "Almond Varieties in 
 the United States, U. S. D. A., Dept. Bull. 1282, 1924. 
 
ClBC. 284] THE ALMOND IN CALIFORNIA 49 
 
 varietal variation in season, appearance, texture, flavor, and behavior 
 that is found in the apple, peach, pear, and similar fruits. With 
 almonds, the season of all varieties extends from one harvest to the 
 next, if properly handled. Growers are, therefore, recommended to 
 plant only standard, marketable varieties so far as possible. 
 
 Early ripening varieties are best. The crop should be in the 
 hands of the trade early, for the bulk of it is used in the holiday 
 trade. This is especially true of unshelled almonds. Moreover, only 
 early almonds can be harvested and sold before the bulk of the Euro- 
 pean shipments arrive. 
 
 The same variety often ripens at slightly different times in differ- 
 ent seasons, in different sections and even in different orchards in 
 the same season. Generally, harvesting commences early in August 
 and closes about the middle of October. The approximate order in 
 which the better known varieties ripen is shown in table 5. 
 
 TABLE 5 
 Approximate Order of Ripening of Varieties of Almonds 
 
 1. Nonpareil 
 
 4. Peerless 
 
 5. Golden State 
 
 2. I. X. L. 
 
 Princess 
 
 6. Lewelling 
 
 Eureka 
 
 California 
 
 7. Drake 
 
 Jordan 
 
 King 
 
 8. Languedoc 
 
 3. Ne Plus Ultra 
 
 Silver 
 
 Texas 
 9. Reams 
 
 Many new varieties have been originated in California, but most 
 of them have fallen into disfavor in a short time. In fact, it is 
 impossible now to find even single trees of some varieties which 
 were formerly well known. From time to time, however, worthy 
 varieties have been introduced and have succeeded in making a per- 
 manent place for themselves through their ability to fill a demand that 
 before had been but partially or poorly supplied. 
 
 In view of the changing market situation for California almonds, 
 due to the rapidly increasing acreage and to the very limited demand 
 for unshelled almonds, it is safe to predict that the only new varieties 
 which will be of value in the future will be those that are primarily 
 of superior quality for shelling purposes. Yield must take second 
 place. 
 
 Well-known varieties are not only in greater demand in the prin- 
 cipal markets, but they invariably bring much better prices than the 
 newer varieties. In some years, when the domestic crop of a given 
 
50 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 variety is light and the demand good, it is possible to unload poorer 
 or less known varieties at fairly good prices. More often, however, 
 they are a drug on the market. 
 
 All varieties will vary in size from season to season and in different 
 orchards during the same season, according to the plant food and 
 moisture supply available during the time the nuts are maturing. 
 
 i 
 
 
 « ■"-' * 
 
 Fig. 14. — Typical Nonpareil almond tree in University Farm orchard; nine 
 years old. Note numerous watersprouts which must be removed. 
 
 Some varieties, notably the Nonpareil, vary more in size than in 
 plumpness, while others, like the Ne Plus Ultra, are more inclined to 
 produce somewhat shriveled kernels and imperfectly developed shells 
 though the variation in size will not be so great. As the yields become 
 heavier, the nuts are likely to be smaller. Young, vigorous trees with 
 a light crop often produce unusually large nuts with comparatively 
 thin shells. The value of a variety, therefore, depends largely upon 
 its behavior after the trees reach full maturity and bearing. 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 51 
 
 Varieties Recommended. — The best marketable nuts are, as has 
 been suggested, few in number, and most of these do well in all of 
 the principal almond districts of California. Where the climatic and 
 soil conditions are favorable there is no great difference in the be- 
 havior of the several varieties, but where these conditions are not so 
 favorable certain varieties do better than others. 
 
 The Nonpareil (fig. 14), the best variety known at the present 
 time for California conditions, bears more nearly uniform crops from 
 year to year and shows a wider range of adaptation than any of the 
 
 
 Fig. 15. — Typical Drake almond tree in University Farm orchard; nine years old. 
 
 other good commercial varieties. It has proved itself to be satisfac- 
 tory in every almond district in the state. The Drake (fig. 15) closely 
 approaches the Nonpareil in this respect. The I. X. L. (fig. 16) and 
 Ne Plus Ultra (fig. 17) are the most variable in their behavior. The 
 blossoms of these two varieties seem to be more tender and hence 
 more liable to injury under unfavorable conditions ; gumming is more 
 prevalent near the coast, and during harvest the slower ripening and 
 opening of the hulls in the more moist atmosphere in many of the coast 
 valleys cause excessive darkening and sometimes molding of the shell. 
 The Ne Plus Ultra does best on comparatively high, well-drained soils, 
 adjacent to the larger streams in the Sacramento valley, such as the 
 lands along the Sacramento River, Putah Creek, Cache Creek, etc. 
 It grows and produces well in the Banning district and in many of 
 
52 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 the foothill sections where conditions are favorable. The I. X. L. 
 does best on the foothills surrounding the Sacramento Valley, par- 
 ticularly on the west side. Varieties which ripen later than the Drake 
 should be avoided in the Banning district and other sections of 
 similar climatic conditions because of the liability to damage from the 
 frequent October rains. 
 
 Hi 
 
 Fig. 16. — Typical I. X. L. almond tree in University Farm orchard; nine years old. 
 
 Doubtful and Undesirable Varieties. — There are a number of 
 different varieties, such as the Eureka and Jordan which give prom- 
 ise of filling a limited place in the markets, but which have not yet 
 been thoroughly tested throughout the state. It is still a question 
 as to whether growing them in very large quantities would affect the 
 price. The Jordan nut is of excellent quality, but in California the 
 trees are variable in vigor. In some cases the trees make unusually 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 53 
 
 large, vigorous growth, while in others they are small and apparently 
 stunted. In general, the Jordans do not hear sufficiently heavy crops 
 to make them pay at the prevailing low [trices. 
 
 ... 
 
 •■» 
 
 w 
 
 - ~V 
 
 Fig. 17. — Typical No Plus Ultra almond tree in University Farm orchard: nine 
 years old. 
 
 Other varieties, such as the Texas, have been sufficiently tested 
 to show their adaptability to most districts, but they are not recom- 
 mended because of the difficulty experienced in marketing them at 
 a profit in large quantities. The Texas has been planted extensively 
 
54 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 in California without sufficient justification. It was planted because 
 of its value as a pollinizer, and of its precocious and prolific bearing. 
 In small quantities it was sold in less exacting markets as a Drake, 
 but in larger quantities the trade has objected to it. Its lateness 
 in ripening is making it harder each year satisfactorily to market 
 the rapidly increasing tonnage of this variety. It should, therefore, 
 be avoided in new plantings. 
 
 Unshelled Almonds. — Athough future markets will no doubt use 
 shelled almonds very largely, there will always be a limited demand 
 for unshelled almonds for use in the holiday trade and for home 
 table use. Unshelled almonds for such purposes must be large, 
 attractive nuts with light-colored, clean-looking shells, soft enough 
 to be broken with the hands. The kernels must be well filled and free 
 from gum. The I. X. L. is the most popular and highest priced nut 
 for these purposes. The Ne Plus Ultra ranks next because of its 
 attractive outside appearance and shape, one of the principal objec- 
 tions to it being its tendency to have gummy kernels. The Drake is 
 another variety in demand by the holiday trade. It is moderately 
 large, plump, and well filled with a good kernel and while not so 
 attractive as the I. X. L. or Ne Plus Ultra, it is one of the most 
 popular medium priced nuts. A certain class of trade prefers the 
 Nonpareil, which appears to be growing in popularity because of the 
 attractive kernel and the ease with which it may be shelled by hand. 
 
 Shelled Almonds. — The confectioners, on the other hand, care 
 nothing for the shell. They want a medium or large sized kernel, 
 uniform in shape, and plump ; one that can be coated smoothly or 
 evenly with candy. For blanching and salting purposes, the kernels 
 must be large and smooth. The best California variety for this pur- 
 pose is the Nonpareil. It is also the best nut for table use when sold 
 unshelled. As a rule, the papershell varieties are the best for shell- 
 ing because of the large percentage of unbroken kernels which may 
 be obtained. The broken kernels and those obtained from cheaper and 
 less desirable varieties are used largely by the bakers and almond- 
 paste manufacturers. 
 
 Owing to the increasing consumption of shelled almonds and the 
 probability of a still greater increase in the future, growers should 
 arrange future plantings with a view to supplying the best shelling 
 varieties. At the present time, the best shelling varieties are not 
 ordinarily the heaviest producers. With a limited production they 
 may not even bring as large returns as the poorer but heavier yield- 
 ing varieties. As the production increases, which it is doing very 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 55 
 
 rapidly, the relative value of the best shelling varieties will increase 
 in proportion and bring good prices when it will be impossible to 
 move at a profit a heavy tonnage of a poor variety. 
 
 Size of Almonds — Per Cent of Kernels and Per Cent of Doubles. 
 — Records of fourteen varieties of almonds grown in the same 
 orchard under similar conditions of soil and culture have been kept 
 at the University Farm at Davis, for the years 1913 to 1916 inclusive. 
 These trees are all of the same age, except the Texas, Peerless, and 
 Harriott, which are one year younger than the others. The figures 
 in table 6 show that there is a wide variation among varieties, as 
 regards not only the size, but the proportion of shell to the whole 
 nut, and the proportion of double kernels. 
 
 TABLE 6 
 
 Showing Number per Pound, Per Cent of Kernels, and Proportion of 
 
 Double Kernels 
 
 Variety 
 
 Nonpareil 
 
 I. X. L 
 
 Ne Plus Ultra 
 
 Drake 
 
 Languedoc 
 
 Texas 
 
 Reams 
 
 Lewelling 
 
 Peerless 
 
 Princess 
 
 California 
 
 King 
 
 Harriott 
 
 Jordan 
 
 Number of nuts 
 per pound 
 
 236 
 152 
 167 
 145.5 
 211 
 173 
 140.5 
 150 
 124 
 238 
 216 
 241 
 167 
 74 
 
 Weight per cent 
 of kernels to 
 whole nuts 
 
 52.28 
 
 56.45 
 
 44.48 
 
 49.16 
 
 43.89 
 
 45.27 
 
 46.96 
 
 36.05 
 
 70.6 
 
 70.43 
 
 71.2 
 
 53.68 
 
 25.23 
 
 Number per cent 
 
 of double 
 
 kernels 
 
 3.05 
 
 .60 
 7.37 
 8.54 
 
 .97 
 
 10.29 
 
 9.51 
 
 29.50 
 
 6.62 
 
 1.88 
 
 .032 
 1.14 
 
 .88 
 2.93 
 
 The above figures are for hand-shelled almonds from young trees. 
 It must be remembered that the figures will vary on older trees and 
 also that the percentage of kernel to whole nuts will be lower for 
 samples from commercial shelling plants. 
 
 Methods of Classification. — Almonds are classified according to 
 hardness of shell: 
 
 Papershell. — Those having a thin, papery shell which may be 
 broken easily between the fingers of one hand. 
 
 Softshell. — Those which have a more or less spongy or thin shell 
 which may be broken between the fingers of two hands. 
 
56 
 
 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 
 
 Standardshell. — Those requiring very strong pressure of the hand 
 or the use of a nut-craeker to break. These may have a spongy or 
 smooth outer shell. 
 
 Hardshell. — Those which cannot be broken by hand but require a 
 sharp blow with a hammer or strong pressure with a nut-cracker to 
 crack them. 
 
 The papershell varieties are excellent for shelling, as they contain 
 a large percentage of kernels which may easily be obtained whole. 
 
 'x 
 
 Fig. 18. — Almond varieties. 
 
 The principal objections are that birds are particularly fond of them 
 since they can crack them easily, and that the shells are often poorly 
 sealed. The latter fact makes it difficult to prevent worm infestation 
 and the entrance of sulphur fumes into the kernel during the bleach- 
 ing process. As a result, practically none of the papershells are 
 bleached but are sold for shelling purposes. 
 
 The softshells are generally more attractive for table use because 
 the shells are more perfect and, in commercial varieties, are brighter 
 in color and more attractive. The shells are usually well sealed and 
 can be bleached to give additional brightness with less danger of the 
 fumes penetrating to the kernel than in the case of the papershells. 
 
Circ. 284] 
 
 THE ALMOND IN CALIFORNIA 
 
 57 
 
 The standardshells have the greatest range in character, thickness, 
 and hardness of shell. The percentage of kernel is too low to make 
 them very attractive to the retail trade. Of this class the Drake is 
 probably the best of the California varieties. Almond varieties of all 
 these classes are shown in figures 18 and 19. These illustrations show 
 most of the varieties grown to any extent in California and others that 
 have attracted much interest and inquiry, together with the European 
 Tarragona. 
 
 
 
 ; v>V' 
 
 *. 
 
 • A 
 
 ■ mmm** 
 
 fe-^S*^ 
 
 Fig. 19. — Almond varieties. 
 
 ACKNOWLEDGMENTS 
 
 The writers desire to express their appreciation to the California 
 Almond Growers' Exchange, and to Mr. M. N. Wood, Pomologist, 
 U. S. Department of Agriculture, who have provided certain data and 
 given helpful suggestions, and to acknowledge the help and sugges- 
 tions received from Dr. W. L. Howard, who gave valuable assistance 
 in the preparation of the manuscript. 
 
STATION PUBLICATIONS AVAILABLE FOR FRPJE DISTRIBUTION 
 
 BULLETINS 
 
 No. No. 
 
 253. Irrigation and Soil Conditions in the 352. 
 Sierra Nevada Foothills, California. 
 
 261. Melaxuma of the Walnut, "Juglans 353. 
 
 regia." 354. 
 
 262. Citrus Diseases of Florida and Cuba 357. 
 
 Compared with Those of California. 
 
 263. Size Grades for Ripe Olives. 
 
 268. Growing and Grafting Olive Seedlings. 358. 
 273. Preliminary Report on Kearney Vine- 
 yard Experimental Drain. 359. 
 
 275. The Cultivation of Belladonna in Cali- 361. 
 
 fornia. 
 
 276. The Pomegranate. 362. 
 
 277. Sudan Grass 363. 
 
 278. Grain Sorghums. 
 
 279. Irrigation of Rice in California. 364. 
 
 280. Irrigation of Alfalfa in the Sacramento 
 
 Valley. 366. 
 
 283. The Olive Insects of California. 
 
 285. The Milk Goat in California. 367. 
 
 286. Commercial Fertilizers. 
 
 294. Bean Culture in California. 368. 
 304. A Study of the Effects of Freezes on 
 
 Citrus in California. 369. 
 
 310. Plum Pollination. 370. 
 
 312. Mariout Barley. 371. 
 
 313. Pruning Young Deciduous Fruit Trees. 
 
 319. Caprifigs and Caprification. 372. 
 
 324. Storage of Perishable Fruit at Freezing 
 
 Temperatures. 374. 
 
 325. Rice Irrigation Measurements and Ex- 
 
 periments in Sacramento Valley, 
 1914-1919. 375. 
 
 328. Prune Growing in California. 
 
 331. Phylloxera-Resistant Stocks. 376. 
 
 334. Preliminary Volume Tables for Second- 
 
 Growth Redwood. 377. 
 
 335. Cocoanut Meal as a Feed for Dairy 379. 
 
 Cows and Other Livestock. 380. 
 
 339. The Relative Cost of Making Logs from 
 
 Small and Large Timber. 381. 
 
 340. Control of the Pocket Gopher in Cali- 
 
 fornia. 382. 
 
 343. Cheese Pests and Their Control. 
 
 344. Cold Storage as an Aid to the Market- 383. 
 
 ing of Plums. 
 
 346. Almond Pollination. 384. 
 
 347. The Control of Red Spiders in Decidu- 
 
 ous Orchards. 
 
 348. Pruning Young Olive Trees. 385. 
 
 349. A Study of Sidedraft and Tractor 386. 
 
 Hitches. 
 
 350. Agriculture in Cut-over Redwood Lands. 
 
 Further Experiments in Plum Pollina- 
 tion. 
 
 Bovine Infectious Abortion. 
 
 Results of Rice Experiments in 1922. 
 
 A Self-mixing Dusting Machine for 
 Applying Dry Insecticides and 
 Fungicides. 
 
 Black Measles, Water Berries, and 
 Related Vine Troubles. 
 
 Fruit Beverage Investigations. 
 
 Preliminary Yield Tables for Second 
 Growth Redwood. 
 
 Dust and the Tractor Engine. 
 
 The Pruning of Citrus Trees in Cali- 
 fornia. 
 
 Fungicidal Dusts for the Control of 
 Bunt. 
 
 Turkish Tobacco Culture, Curing and 
 Marketing. 
 
 Methods of Harvesting and Irrigation 
 in Relation to Mouldy Walnuts. 
 
 Bacterial Decomposition of Olives dur- 
 ing Pickling. 
 
 Comparison of Woods for Butter Boxes. 
 
 Browning of Yellow Newtown Apples. 
 
 The Relative Cost of Yarding Small 
 and Large Timber. 
 
 The Cost of Producing Market Milk and 
 Butterfat on 246 California Dairies. 
 
 A Survey of Orchard Practices in the 
 Citrus Industry of Southern Cali- 
 fornia. 
 
 Results of Rice Experiments at Cor- 
 tena, 1923. 
 
 Sun-Drying and Dehydration of Wal- 
 nuts. 
 
 The Cold Storage of Pears. 
 
 Walnut Culture in California. 
 
 Growth of Eucalyptus in California 
 Plantations. 
 
 Growing and Handling Asparagus 
 Crowns. 
 
 Pumping for Drainage in the San 
 Joaquin Valley, California. 
 
 Monilia Blossom Blight (Brown Rot) 
 of Apricot. 
 
 A Study of the Relative Values of Cer- 
 tain Succulent Feeds and Alfalfa Meal 
 as Sourses of Vitamin A for Poultry. 
 
 Pollination of the Sweet Cherry. 
 
 Pruning Bearing Deciduous Fruit 
 Trees. 
 
 CIRCULARS 
 
 No. No. 
 
 87. Alfalfa. 155. 
 
 113. Correspondence Courses in Agriculture. 157. 
 
 117. The Selection and Cost of a Small 160. 
 
 Pumping Plant. 161. 
 
 127. House Fumigation. 164. 
 
 129. The Control of Citrus Insects. 165. 
 136. Melilotus indira as a Green-Manure 
 
 Crop for California. 166. 
 
 144. Oidium or Powdery Mildew of the Vine. 167. 
 
 151. Feeding and Management of Hogs. 170. 
 
 152. Some Observations on the Bulk Hand- 
 
 ling of Grain in California. 173. 
 154. Irrigation Practice in Growing Small 
 
 Fruit in California. 178. 
 
 Bovine Tuberculosis. 
 
 Control of the Pear Scab. 
 
 Lettuce Growing in California. 
 
 Potatoes in California. 
 
 Small Fruit Culture in California. 
 
 Fundamentals of Sugar Beet Culture 
 
 under California Conditions. 
 The County Farm Bureau. 
 Feeding Stuffs of Minor Importance. 
 Fertilizing California Soils for the 1918 
 
 Crop. 
 The Construction of the Wood-Hoop 
 
 Silo. 
 The Packing of Apples in California. 
 
CIRCULARS — {Continued) 
 
 No. 
 179. 
 
 184. 
 190. 
 199. 
 202. 
 
 203. 
 208. 
 
 209. 
 210. 
 212. 
 214. 
 
 215. 
 217. 
 
 220. 
 228. 
 231. 
 232. 
 
 233. 
 234. 
 
 235. 
 
 236. 
 
 237. 
 
 238. 
 239. 
 
 240. 
 
 241. 
 
 243. 
 
 244. 
 245. 
 247. 
 248. 
 
 249. 
 250. 
 
 Factors of Importance in Producing 
 
 Milk of Low Bacterial Count. 
 A Flock of Sheep on the Farm. 
 Agriculture Clubs in California. 
 Onion Growing in California. 
 County Organizations for Rural Fire 
 
 Control. 
 Peat as a Manure Substitute. 
 Summary of the Annual Reports of the 
 
 Farm Advisors of California. 
 The Function of the Farm Bureau. 
 Suggestions to the Settler in California. 
 Salvaging Rain-Damaged Prunes. 
 Seed Treatment for the Prevention of 
 
 Cereal Smuts. 
 Feeding Dairy Cows in California. 
 Methods for Marketing Vegetables in 
 
 California. 
 Unfermented Fruit Juices. 
 Vineyard Irrigation in Arid Climates. 
 The Home Vineyard. 
 Harvesting and Handling California 
 
 Cherries for Eastern Shipment. 
 Artificial Incubation. 
 Winter Injury to Young Walnut Trees 
 
 during 1921-22. 
 Soil Analysis and Soil and Plant Inter- 
 relations. 
 
 The Common Hawks and Owls of Cali- 
 fornia from the Standpoint of the 
 
 Rancher. 
 Directions for the Tanning and Dress- 
 
 of Furs. 
 The Apricot in California. 
 Harvesting and Handling Apricots and 
 
 Plums for Eastern Shipment. 
 Harvesting and Handling Pears for 
 
 Eastern Shipment. 
 Harvesting and Handling Peaches for 
 
 Eastern Shipment. 
 Marmalade Juice and Jelly Juice from 
 
 Citrus Fruits. 
 Central Wire Bracing for Fruit Trees. 
 Vine Pruning Systems. 
 Colonization and Rural Development. 
 Some Common Errors in Vine Pruning 
 
 and Their Remedies. 
 Replacing Missing Vines. 
 Measurement of Irrigation Water on 
 
 the Farm. 
 
 No. 
 251. 
 
 252. 
 253. 
 254. 
 
 255. 
 
 256. 
 257. 
 258. 
 259. 
 260. 
 
 261. 
 262. 
 263. 
 264. 
 
 265. 
 266. 
 
 267. 
 
 268. 
 
 269. 
 270. 
 271. 
 272. 
 
 273. 
 275. 
 
 276. 
 
 277. 
 
 278. 
 279. 
 281. 
 
 282. 
 
 Recommendations Concerning the Com- 
 mon Diseases and Parasites of 
 Poultry in California. 
 
 Supports for Vines. 
 
 Vineyard Plans. 
 
 The Use of Artificial Light to Increase 
 Winter Egg Production. 
 
 Leguminous Plants as Organic Fertil- 
 izer in California Agriculture. 
 
 The Control of Wild Morning Glory. 
 
 The Small-Seeded Horse Bean. 
 
 Thinning Deciduous Fruits. 
 
 Pear By-products. 
 
 A Selected List of References Relating 
 to Irrigation in California. 
 
 Sewing Grain Sacks. 
 
 Cabbage Growing in California. 
 
 Tomato Production in California. 
 
 Preliminary Essentials to Bovine Tuber- 
 culosis Control. 
 
 Plant Disease and Pest Control. 
 
 Analyzing the Citrus Orchard by Means 
 of Simple Tree Records. 
 
 The Tendency of Tractors to Rise in 
 Front; Causes and Remedies. 
 
 Inexpensive Lavor-saving Poultry Ap- 
 pliances. 
 
 An Orchard Brush Burner. 
 
 A Farm Septic Tank. 
 
 Brooding Chicks Artificially. 
 
 California Farm Tenancy and Methods 
 of Leasing. 
 
 Saving the Gophered Citrus Tree. 
 
 Marketable California Decorative 
 Greens. 
 
 Home Canning. 
 
 Head, Cane, and Cordon Pruning of 
 Vines. 
 
 Olive Pickling in Mediterranean Coun- 
 tries. 
 
 The Preparation and Refining of Olive 
 Oil in Southern Europe. 
 
 The Results of a Survey to Determine 
 the Cost of Producing Beef in Cali- 
 fornia. 
 
 Prevention of Insect Attack on Stored 
 Grain. 
 
 The publications listed above may be had by addressing 
 
 College of Agriculture, 
 
 University of California, 
 
 Berkeley, California. 
 
 15m-4,'25