Almond Pol 1 nation barren P. Tufts and Guy L. Philp pfe *f 301 ' 80J 8 PRINT - G UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA ALMOND POLLINATION BY WARREN P. TUFTS AND GUY L. PHILP BULLETIN 346 JULY, 1922 UNIVERSITY OF CALIFORNIA PRESS BERKELEY, CALIFORNIA 1922 DAVID P. BARROWS, President of the University. EXPEEIMENT STATION STAFF HEADS OF DIVISIONS THOMAS FORSYTH HUNT, Dean. EDWARD J. WICKSON, Horticulture (Emeritus). -- , Director of Resident Instruction C. M. HARINQ, Veterinary Science, Director of Agricultural Experiment Station. B. H. CROCHERON, Director of Agricultural Extension. C. B. HUTCHISON, Plant Breeding, Director of the Branch of the College of Agriculture at Davis. H. J. WEBBER, Subtropical Horticulture, Director of Citrus Experiment Station. WILLIAM A. SETCHELL, Botany. MYER E. JAFFA, Nutrition. RALPH E. SMITH, Plant Pathology. JOHN W. GILMORE, Agronomy. CHARLES F. SHAW, Soil Technology. JOHN W. GREGG, Landscape Gardening and Floriculture. FREDERIC T. BIOLETTI, Viticulture and Fruit Products. WARREN T. CLARKE, Agricultural Extension. ERNEST B. BABCOCK, Genetics. GORDON H. TRUE, Animal Husbandry. WALTER MULFORD, Forestry. JAMES T. BARRETT, Plant Pathology. > FRITZ W. WOLL, Animal Nutrition. W. P. KELLEY, Agricultural Chemistry. H. J. QUAYLE, Entomology. ELWOOD MEAD, Rural Institutions. H. S. REED, Plant Physiology. L. D. BATCHELOR, Orchard Management. W. L. HOWARD, Pomology. * FRANK ADAMS, Irrigation Investigations. C. L. ROADHOUSE, Dairy Industry. R. L. ADAMS, Farm Management. W. B. HERMS, Entomology and Parasitology. JOHN E. DOUGHERTY, Poultry Husbandry. D. R. HOAGLAND, Plant Nutrition. G. H. HART, Veterinary Science. L. J. FLETCHER, Agricultural Engineering. EDWIN C. VOORHIES, Assistant to the Dean. W. L." HOWARD* '' ' *F- "$> AULEN * * v Os'Il "AUSTIN W.-./P. .TUFTJS.-; I .. '3- P.; BflNis'BTT .; ., .'. L.H/-DA? K. .L. XyCEUHoiisEfe . .& JU! PijiBP-* :* :y. "^ ' , \l .* J.'HEVPNER A. H. HENDRICKSON' W. P. DURUZ E. M* Russ L. C. BARNARD * In cooperation with Division of Agricultural Engineering, Bureau of Public Roads, U. S. Department of Agriculture. ALMOND POLLINATION 1 BY WARREN P. TUFTS AND GUY L. PHILP For the successful production of orchard crops certain important limiting factors are to be considered. In the culture of the almond, freedom from late spring frosts, a deep well-drained soil, and the interplanting of proper varieties to secure cross-pollination are the chief "limiters." Almonds were planted in California as early as 1853, but records show that the tonnage of the early orchards was very variable. The vj failure was due largely to a lack of knowledge of the factors con- 's trolling the successful production of the almond. Gradually it became recognized that the almond, on account of its early blooming habit , (in certain sections of California sometimes as early as late January), and its aversion to heavy and poorly-drained soils, would succeed ^ commercially only in certain locations, that is, where there is little i danger from late spring frosts and where the soil is deep and well drained. That there is a distinct pollination problem with the almond was > recognized as early as 1885, when Mr. A. T. Hatch, 2 of Suisun, Cali- ^i J^i fornia, pointed out the fact that Languedoc trees near seedlings always \^ produced heavier crops than when planted in solid blocks. On account of its reputation for light bearing the Languedoc variety was rapidly \ displaced by the Nonpareil, I. X. L., and Ne Plus Ultra varieties, 4^ seedlings originated and introduced by Mr. Hatch in the early 90 's. ^ Many of the later orchards were also planted in unsuitable places, there being a feeling that these new improved varieties would prove profitable under all conditions. In addition to the failure of the orchards planted in unfavorable locations, many instances 3 are on record as to the non-bearing of the Hatch varieties where the only plausible explanation is that of lack of proper cross-pollination. 1 This paper is a final report of the work of which a preliminary account was given in California Agricultural Experiment Station Bulletin No. 306, Almond Pollination, by W. P. Tufts, March, 1919. In many particulars this article is identical with the earlier publication, but contains considerable additional data which confirm and strengthen the findings of the station concerning the pollination problem of the almond. 2 California State Board of Horticulture Reports, 1885-1886, p. 326. a Dargitz, J. P., Pacific Rural Press, Vol. 72, No. 10, Sept. 8, 1906. 235278 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION THE PROBLEMS OF ALMOND POLLINATION An attempt has been made to solve the following problems for California conditions: 1. S 'elf '-fertility. 4 What varieties of almonds grown commercially in California will be profitable when planted in solid blocks, i.e., with- out pollenizers.? 2. Self -sterility* What varieties planted in solid blocks will not be profitable? 3. Inter-fertility. If the commercial varieties of almonds at pres- ent grown in California will not produce profitably unless cross- pollination is provided, which varieties should be planted together? Even though two varieties may be inter-fertile, the following points should always be considered in selecting pollenizing varieties: (a) Commercial value of the pollenizer. (&) Coincidence of bloom of the pollenizer with the variety to be pollinated. (c) Succession of the ripening of varieties for convenience in har- vesting. (d) Amount of pollen produced by the pollenizer. (e) Germinability of the pollen produced by the pollenizer. ORGANIZATION OF THE WORK The methods employed for the solution of the problems just out- lined were those commonly in use in cross-pollination experiments. Briefly stated, this part of the work consisted in the application by hand of the pollen desired, having first removed the flowers' own pollen-producing organs (the stamens). The introduction of foreign pollen through the agency of wind and insects was prevented by cover- ing the hand-pollinated blossoms with paper sacks. 5 Accurate counts of flowers of the various varieties thus treated with pollen of different kinds were recorded. Later in the season the sacks were removed. The fruits resulting from these artificial pollinations were counted and the proper records made after the first and second drops and again at harvest. 4 The writers prefer the terms ' ' barren ' ' and ' ' fruitful ' ' as explained by Kraus in the Journal of Heredity, Vol. 6, No. 12, pp. 549-557, rather than the inexact terms, ' ' sterile ' ' and ' ' fertile. ' ' The latter terms have been used in this paper, however, because, as herein used, they are more or less familiar to the general public. 5 The use of paper sacks is probably unnecessary. In fruits like the almond there is practically no wind pollination and insects do not visit emasculated flowers. BULLETIN 346 J ALMOND POLLINATION 5 During 1910 the work was carried on by B. S. Brown," and during 1915 by W. E. Gilfillan. 7 The data for these two years are of little value in themselves, because the numbers employed were relatively small. During 1916 the work was largely confined to the determina- tion of the question of self -sterility, and in 1917 the same work was repeated and many cross-pollinations made. In 1918 repetition of all self-pollinations and crosses was again made, but frost in the Univer- sity orchards at Davis and the G. W. Atterbury orchard at Woodland vitiated the whole season's efforts, with the exception of the experi- ments performed on the Nonpariel variety, which were carried on in the orchard of Mr. G. W. Pierce, some six miles distant from the University Farm. The work of 1918 was repeated during the season of 1919 in the University orchards at Davis. With the exceptions noted all experiments were conducted in the University orchards at Davis. The trees in these orchards were all young and vigorous, having been planted during the spring of 1908. The Pierce orchard was planted in 1892 and the trees were in fair vigor. In the Atterbury orchard the trees were young and vigorous, having been planted in 1914. THE BLOOMING PERIOD OF CERTAIN ALMOND VARIETIES Almonds have a relatively long period of bloom if the total time from the opening of the first blossoms to the shedding of the petals is considered. Many growers arc of the opinion that even the later blooming varieties overlap suffici< ntly with the earlier varieties to set a crop on the latter. Such a selection of varieties, however, is not to be generally advised, although in some cases it may be desired to use a variety listed as an early bloomer to pollenize a late bloomer. Based on what may be called the period of effective bloom, varieties may be roughly divided into early and late bloomers, as shown in the following lists. The Nonpareil has been included in both lists as being just about midway. Early bloomers Late bloomers Big White Flat Klondike Dickinson California Lewelling Drake Eureka Ne Plus Ultra Golden State Harriott Nonpareil Languedoc I. X. L. Peerless Nonpareil Jordan Princess Reams King Silver Shell Sellers Texas 8 Brown, B. S., Almond Culture, a thesis presented in partial fulfillment of the requirements for the Master's degree from the University of California, 1911. 7 Gilfillan, W. E., Pollination of the Almond, a thesis presented in partial fulfillment of the requirements for the Bachelor's degree from the University of California, 1915. b UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The accompanying chart (page 7) gives the average blooming seasons of certain almond varieties for the years 1914 to 1921, in- clusive, unless otherwise noted. The date of bloom is of course dependent on many factors, such as soil, season, and location. Period of Effective iMojjeinino t>f Almondj-Univerjily TFRRIinRV MARCH / FEBRUARY Harriott NePlvurUltrA. I.X.L Peerlejj Jordan Prince,/./ Lewelling California, King Nonpareil Golden Jbvie br.ke Tex.< P p ! n O O B C & B P M 5-- UNIVERSITY OF CALIFORNIA EXPERIMENT STATION POLLEN PRODUCTION OF SEVENTEEN ALMOND VARIETIES (Continued) Pollen production, Pollen production, Pollen production. Variety 1917 1918 1919 Jordan Medium to shy Shy Shy King Medium Medium Abundant Klondike Abundant Medium Abundant Languedoc Very shy Medium to shy Medium Lewelling Abundant Medium Shy Ne Plus Ultra Abundant Abundant Medium Nonpareil Abundant Abundant Abundant Peerless Abundant Abundant Abundant Princess Abundant Abundant Shy Reams Abundant Abundant Abundant Texas Medium to abundant Abundant Very abundant GERMINABILITY OF THE POLLEN USED The pollen used in all experiments was in prime condition and passed in all cases a very satisfactory artificial germination test. In many instances pollen collected from early maturing flowers proved to be of very poor viability as compared with that produced by later blossoms on the same tree. TABLE I GERMINABILITY OF POLLEN, SEASONS 1915-1919 Figures give per cent germination in 12 per cent cane sugar solution. Variety 1915 1916 1917 1918 1919 Big White Flat .... 93 76 75 California 75 37 77 50 Dickinson .... 51 Drake 94 35 33 32 13 Eureka .... .... 14 29 Golden State .... 25 32 13 Harriott 92 76 80 88 50 I. X. L : 85 80 94 60 74 Jordan 73 50 85 64 12 King 80 33 48 54 Klondike .... 89 86 65 Languedoe 44 28 12 15 29 Levelling 88 90 69 65 32 Ne Plus Ultra 89 83 94 74 88 Nonpareil 90 88 53 44 11 Peerless 50 24 60 15 Princess 81 63 39 37 13 Beams 90 .... 53 25 Sellers .... .... 64 1Q Silver Shell .... .... .... 40 Texas 85 86 60 16 Average 82.1 69.5 57.1 52.8 37.0 BULLETIN 346] ALMOND POLLINATION 9 During the first two seasons weather conditions during the bloom- ing period of almonds were favorable for the setting of fruit and, as a consequence, very high germination tests were recorded. During 1917, 1918, and 1919, however, wind, cold, and rain destroyed to a marked degree the viability of the pollen. But inasmuch as only one viable pollen grain is actually necessary to effect fertilization, and since by actual count it was determined that from sixty to one hun- dred and twenty-five pollen grains were deposited on the stigma of each flower artificially pollinated, there need be no fear as to the accuracy of the results because of low viability of the pollen employed. RELATION OF NORMAL SET TO FINAL CROP Immediately after the petals fall each flower begins to form a fruit. During the following two or three weeks a certain percentage of these young fruits drop and only a rather low percentage of the total number of original blossoms continues to develop. It is essential that this drop take place, as the tree under average circumstances would never be able to carry so many fruits through to maturity. The factors determining which of these young fruits shall drop are not at present fully known. Later in the season there takes place still another falling of young fruits known as the "June drop." The expression normal set is a more or less technical term designat- ing the percentage of fruit which the tree sets under normal con- ditions when left open to insect pollination. It is obvious that the normal set may be determined at any time up to the end of the season by counting the fruits on a tree and comparing that number with the original bloom. In these experiments approximately 2000 blossoms of each variety, well distributed over the trees, were counted each year and proper records kept to determine the normal set after the first and the second drop, and at harvest time. The questions at once arise as to what percentage of normal set at harvest time constitutes a full crop and what is meant by a "full crop. ' ' What constitutes a full crop of any fruit is perhaps largely a question of judgment or guess. It varies with such factors as variety, soil, and moisture conditions. What would be considered a full crop under foothill conditions would not necessarily be the same in a valley location. In order to secure some idea on this important phase of the subject, table II is herewith presented which gives the normal set of certain almond varieties for the years 1916, 1917, and 1919, together with the average yield in pounds of these trees reduced to an acreage basis. The trees under observation were planted during the 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION spring of 1908, being set twenty-four feet apart by the square system, which gives approximately seventy-five trees to the acre. Since plant- ing, these trees have received good commercial culture. All figures given are based on the yields of almonds harvested. A brief examination of the table shows that too much stress must not be laid on mere percentages, because during the 1916 season the normal set was much heavier than in 1917 or 1919, but the crop of the latter two years was much heavier. This is easily explained by the relatively heavier bloom during the springs of 1917 and 1919. These figures also emphasize the importance of correct comparisons and show that the normal set must be carefully taken each year in order to secure a correct basis for the comparison of results obtained by arti- ficial pollination. TABLE II COMPARISON OF NORMAL SET WITH YIELD OF ALMONDS IN POUNDS (DRY WEIGHT) PER ACRE 1916 1917 1919 Variety Percentage Lbs. per set acre Percentage set Lbs. pei acre Percentage set Lbs. per acre Big White Flat 13.0 1,402 California 14 869 7.3 865 3.6 1,362 Drake 15 1,229 16.4 3,800 15.5 1,162 Golden State 14.5 2,775 Harriott 16 893 11.9 2,240 8.4 1,650 I. X. L. 17 1,059 16.5 1,515 21.7 1,575 Jordan 13 817 3.6 455 0.3 600 King 29 660 25.7 1,395 26.2 2,047 Klondike 13.2 1,125 Languedoe 22 1,763 16.5 745 10.9 1,391 Lewelling 37 1,235 25.0 2,035 29.7 975 Ne Plus Ultra 28 1,714 20.4 3,670 16.9 1,500 Nonpareil 24 869 28.2 2,415 Peerless 20 888 7.0 895 9.0 1,950 Princess 17 935 17.7 1,275 13.9 1,905 Beams 23 2,044 14.0 2,905 18.0 1,950 Silver Shell .... 10.0 1,125 Texas 39 1,657 21.7 1,430 39.0 1,308 Average 22.3 1,189 16.6 1,885 15.5 1,522 NORMAL SET OF ALMOND VARIETIES There is presented in table III a record of the normal set of various almond varieties under test at the University Farm. It will be noted that the normal set in the University orchards with open pollination ranged all the way from 0.3 per cent, in the case of the Jordan in BULLETIN 346] ALMOND POLLINATION 11 1939, to 39 per cent, in the case of the Texas, in 1916 and 1919. Prob- ably due to unfavorable weather conditions at the time of blossoming, the set during 1917 and 1919 on the whole, was somewhat lower than that of 1916, the average being 15.7 per cent, 16.6 per cent, and 22.3 per cent, in 1919, 1917, and 1916, respectively. On account of the heavier bloom, however, the crop was considerably heavier in 1917 than in either 1916 or 1919 ; however, certain varieties, King for example, produced a much heavier crop with practically the same percentage of blossoms setting, in 1919. Attention is also called to the fact that in the orchard of Mr. G. W. Pierce (table VI) the set was considerably lower than at the University Farm. This is ex- plained by the fact that in Mr. Pierce 's orchard practically no insect pollen carriers were present. The orchard is properly inter-planted with pollenizing varieties. TABLE III NORMAL SET OP FRUIT ON ALMOND VARIETIES 1916, 1917, 1919 University Farm, Davis, California. 1916 Number Percentage blossoms matured Variety counted Big White Flat California 2,402 14 Drake 2,141 15 Eureka Golden State Harriott 1,961 16 I. X. L. 2,131 17 Jordan 1,970 13 King 1,675 29 Klondike Languedoc 2,294 22 Lewelling 2,151 37 Ne Plus Ultra 2,071 26 Nonpareil 1,989 24 Peerless 1,975 20 Princess 2,085 17 Sellers Silver Shell Beams 1,910 23 Texas 2,019 39 1917 A Number blossoms counted Percentage matured 1,083 14.2 2,707 7.3 2,752 16.4 1,044 30.0 2,301 11.9 2,663 16.5 2,593 3.6 2,512 25.7 1,069 30.4 2,488 16.5 2,653 25.0 1,953 20.4 2,647 28.2 1,925 7.0 2,731 17.7 742 17.7 2,001 14.0 2,568 21.7 1919 Number blossoms counted Percentae* matured 1,091 13.0 2,577 3.6 2,339 15.5 336 16.9 1,022 14.5 1,175 8.4 2,751 21.7 2,534 0.3 2,533 26.2 2,893 13.2 3,003 10.9 2,190 29.7 2,886 16.9 2,757 9.0 2,426 13.9 1,279 17.8 1,070 10.0 2,828 18.0 2,556 39.0 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION SELF-STERILITY IN VARIOUS ALMOND VARIETIES 1916, 1917, 1919 Table IV gives the self-pollination record of the almond varieties tested for self -sterility during 1916, 1917, and 1919. From this table it will be noted that all of the twenty varieties tested gave distinct evidence of self-sterility. The Harriott variety in 1916 proved self- fertile, but in 1917 and 1919 was decidedly self-sterile. The probable explanation is that this variety behaves like certain varieties of apples and pears which one season may be self-sterile, while another season they may be partly self-fertile. It is possible, however, that this variety was cross-pollinated by mistake in 1916. The results of these three seasons 1916, 1917, and 1919 and also 1910 and 1911 are the same, viz., that for all practical purposes the cultivated almond is self-sterile and in all cases orchards must be inter-planted with pollenizing varieties if they are to prove commercially profitable. Variety Big White Flat California Drake Eureka Golden State Harriott I. X. L Jordan King Klondike Languedoc Lewelling Ne Plus Ultra Nonpareil Peerless Princess Sellers Silver Shell Texas Note. A in orchard. P in orchard. TABLE IV SELF-POLLINATION OP ALMOND VARIETIES 1916, 1917, 1919 University Farm, Davis, California 1916 1917 1919 Number Blossoms Self- Pollinated Percentage Matured Number Blossoms Self- Pollinated 673 Percentage Matured 2.5 Number Blossoms Self- Pollinated 504 Percentage Matured .2 1586 .13 464 268 996 .1 953 410 A 402 .2 554 .4 939 15.0 1189 .08 588 1.3 740 .5 403 .25 403 819 .2 597 299 450 900 404 .49 448 481 979 .1 625 557 .2 1031 .97 960 .63 408 1005 .6 327 .9 469 .4 723 .14 446 .22 P180 976 237 346 .28 822 711 406 355 1.4 376 1064 1015 .09 499 1.2 1029 994 .2 530 the above table indicates that the work was done in the Atterbury the above table indicates that the work was done in the Pierce BULLETIN 346] ALMOND POLLINATION 13 CROSSES BETWEEN CERTAIN ALMOND VARIETIES Tables V and VI give the results of artificial cross-pollinations dur- ing the years 1916, 1917, 1918, and 1919. TABLE V CROSS-POLLINATION OF ALMOND VARIETIES 1916, 1917, 1919 University Farm, Davis, California. 1916 1917 Variety Big White Flat x Harriott x Ne Plus Ultra California x Drake x I. X. L. x Jordan x Ne Plus Ultra x Nonpareil x Peerless Drake x California x Eureka x I. X. L. x Jordan x Languedoc x Ne Plus Ultra x Nonpareil x Peerless x Texas Eureka (A) x Drake x Nonpareil Golden State x Drake x Nonpareil Harriott x Big White Flat x I. X. L. x Ne Plus Ultra 1919 Number Blossoms Hand- Pollinated Percentage Number Blossoms Hand- Percentage Number Blossoms Hand- Percentase Matured Pollinated Matured Pollinated Matured 211 258 257 "250 208 505 3.3 5.8 3.9 12.8 8.2 24.6 514 15.1 274 24.6 . . 499 14.6 980 22.8 450 16.0 502 17.5 511 20.0 563 14.6 523 486 408 482 366 477 484 423 438 436 478 466 477 422 422 425 470 359 458 248 294 376 329 274 5.9 1.4 25.5 25.9 8.4 6.2 30.9 3.0 29.4 11.9 19.8 16.0 14.6 28.9 22.2 21.1 26.4 14.7 15.3 35.9 38.4 30.8 23.4 24.8 Note. (A) in the above table indicates that crosses thus marked were per- formed in the G. W. Atterbury orchard, Woodland, California. 14 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION TABLE V (Continued) 1916 1917 1919 Number Number Number Variety Blossoms Blossoms Blossoms Hand- Percentage Hand- Percentage Hand- Percentage /. X. L. Pollinated Matured Pollinated Matured Pollinated Matured x Drake 145 1.4 413 9.6 x California 364 21.9 x Jordan 264 2.7 327 37.4 x Lewelling 137 5.6 x Harriott 352 14.8 x Ne Plus Ultra 342 40.0 343 6.6 375 9.8 x Nonpareil 484 .8 412 411 x Peerless 404 3.0 413 23.2 Jordan x California 165 0.6 220 3.8 x I. X. L. 139 3.6 242 3.8 x Ne Plus Ultra 183 225 5.7 x Nonpareil 179 1.7 480 4.8 x Peerless 227 .9 King x Ne Plus Ultra 331 41.6 x Nonpareil 100 32.0 Klondike x Ne Plus Ultra 384 14.8 Languedoc x California 502 12.9 497 17.9 x Drake 429 14.9 265 11.7 x Eureka 276 16.9 x I. X. L. 467 5.4 413 9.9 x Ne Plus Ultra 514 9.7 348 8.6 x Nonpareil 471 4.9 558 10.5 x Peerless 457 11.8 292 4.4 x Reams 475 7.6 337 10.3 x Texas 450 433 Lewelling x California 540 10.9 x I. X. L. 424 6.6 442 28.0 x Ne Plus Ultra 373 6.4 486 20.9 x Nonpareil 244 7.5 175 29.1 Ne Plus Ultra x California P308 7.8 450 10.4 x Drake 252 4.4 x Harriott 266 9.7 580 36.0 x I. X. L. 492 36.0 P477 18.4 P478 31.0 x Jordan P160 12.5 325 21.5 x King 94 19.1 x Lewelling 287 8.4 379 12.9 x Nonpareil 482 17.0 223 12.5 404 23.0 x Peerless 104 9.6 Note.(PJ in the above table indicates that crosses thus marked were per formed in the G. W. Pierce orchards, Davis, California. BULLETIN 346] ALMOND POLLINATION 15 TABLE V (Continued) 1916 1917 1919 Number Number Number Variety Blossoms Blossoms Blossoms Hand- Percentage Hand- Percentage Hand- Percentage Nonpareil Pollinated Matured Pollinated Matured Pollinated Matured x I. X. L. 484 .17 283 .4 x Jordan 401 16.2 x Lewelling 258 22.1 x Ne Plus Ultra 402 26.0 486 25.9 x Peerless 520 12.0 x Texas 500 22.4 Peerless x California 540 4.8 x Drake 394 11.1 x Eureka 439 6.3 x I. X. L. 421 2.8 x Jordan 447 7.7 x Languedoc 245 11.8 x Ne Plus Ultra 427 9.1 x Nonpareil 407 6.3 x Texas 428 10.7 Princess x Ne Plus Ultra 324 16.8 x Nonpareil 223 26.0 Reams x California 306 16.7 458 20.3 x Drake 516 27.1 x I. X. L. 66 21.2 x Languedoc 453 22.9 x Ne Plus Ultra 497 19.5 239 18.9 x Nonpareil 502 18.5 370 27.6 x Texas 509 26.7 460 31.0 Sellers x Drake 324 11.1 x Nonpareil 245 23.4 Silver Shell x Drake 438 17,1 Texas x California 528 8.9 596 24.7 x Drake 478 16.5 364 26.3 x Eureka 456 22.8 x L X. L. 394 19.6 228 27.1 x Languedoc 499 505 x Ne Plus Ultra 418 31.5 x Nonpareil 557 17.8 323 26.3 x Peerless 339 11.5 x Reams 221 31.3 16 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION TABLE VI CROSSES ON NONPAREIL ALMOND 1917, 1918, 1919 G. W. Pierce orchard, near Davis, California 1917 1918 1919 Number Blossoms Number Blossoms Number Blossoms Variety Hand- Percentage Hand- Percentage Hand- Percentage Pollinated Matured Pollinated Matured Pollinated Matured Nonpareil Normal Set 3346 2.8 2633 1.5 2067 6.8 Self-pollinated 572 0. 356 180 x California 392 35.7 348 7.7 514 25.0 x Drake 366 12.7 370 22.0 566 34.1 x Eureka 259 8.8 375 37.6 x Golden State 292 20.2 x I. X. L. 237 801 411 x Jordan 226 9.7 305 30.1 x Languedoc 477 23.9 241 31.2 x Ne Plus Ultra 406 12.5 320 24.3 486 25.9 x Peerless 396 15.8 322 15.9 520 12.0 x Texas 212 29.7 409 21.2 500 22.4 INTER-STERILITY BETWEEN ALMOND VARIETIES In all the reciprocal crosses made, only the I. X. L. and Nonpareil, and the Languedoc and Texas varieties seemed to give distinct evidence of inter-sterility. These cases of inter-sterility have never before been recorded, so far as the writers know. The inter-sterility between I. X. L. and Nonpareil has been experimentally proved in 1915, 1916, 1917, 1918, and 1919 and has also been experienced in practice by many growers; the inter-sterility between Languedoc and Texas was experimentally proved in 1917 and 1919. The parentage of almond varieties at present grown in California is unknown and it is therefore impossible to attempt an explanation of the inter-sterility of these varieties on the basis of relationships. INFLUENCE OF POLLENIZERS ON CERTAIN ALMOND VARIETIES During the season of 1916 reciprocal crosses were made only between the Nonpareil, I. X. L., and Ne Plus Ultra varieties and the results showed the first two to be not only self-sterile, but also inter- sterile, i.e., unable to pollinate themselves or each other. The Ne Plus Ultra fertilized the other two and was in turn successfully fertilized by them. BULLETIN 346] ALMOND POLLINATION 17 More than 50,000 artificial cross-pollinations were made during each of the seasons of 1917, 1918, and 1919. As stated, the entire work of the 1918 season was lost through frost except the crosses on the Nonpareil. Likewise on account of unfavorable weather conditions, rather negative results were obtained with certain varieties during 1917. For the sake of brevity, much of the data collected is omitted, only sufficient being given to prove each point. It is felt that sufficient work has been done to give exact information regarding the planting of orchards to insure safe pollination for the more important varieties of almonds. The investigation of this problem has been confined neither to the varieties at present recommended for planting nor to those now grown commercially in the state, a consideration of several kinds of minor importance having also been included. In making recommendations of varieties for interplanting, the writers have attempted to keep in mind the date of blooming, abundance of pollen, and to a limited extent, the productiveness and commercial value of the pollenizer. 8 Big White Flat. The Harriott is the best pollenizer for the Big White Flat. California. The Nonpareil is the best pollenizer for the California. The I. X. L. and Drake also are good pollenizers for the California. Drake. Nine varieties in all were used as pollenizers for the Drake. These varieties were the California, Eureka, I. X. L., Jordan, Languedoc, Ne Plus Ultra, Nonpareil, Peerless, and Texas. Prefer- ence should be given to the California, Ne Plus Ultra, Nonpareil, and Texas varieties. Eureka. The Drake and Nonpareil are satisfactory pollenizers for the Eureka. Golden State. The Drake and Nonpareil are satisfactory pollen- izers for the Golden State. Harriott. The I. X. L. and Ne Plus Ultra are good pollenizers for the Harriott. I. X. L. The Ne Plus Ultra is a satisfactory pollenizer for the I. X. L. Nonpareil failed in all three years to set fruit on the I. X. L. California, Jordan, and Peerless may be used as pollenizers for the I. X. L. Jordan. No especially good pollenizer has been found for the Jordan, which is notoriously a shy bearer. Ne Plus Ultra and Non- pareil give fairly good results as pollenizers. 8 The reader will find a comprehensive discussion of the proper varieties for the commercial plantation in Taylor's "The Almond in California," Bull. No. 297, Calif. Exp. Station. 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 1O ~ ?> ' O vO 1 --- ff B5 1 * 5 2 o x x x x Cf o ^4 ^r o o */) ^ ^- 5 C^ I 2 o9 s I c D i , DC 10 10 o 6 AJ o Ci vO ^ ^ O dj X X X X BULLETIN 346] ALMOND POLLINATION 19 2 .5 *> 5> r &. o * fl a 'S O & -= o) a o PH*S o 2? aj a si a S o CD V~ 7^0 A, to vi aj^. da i in ss i cc K 10 oo o 03 3 5-s bC^ a _ "C "o 355 fluen rietie -' |2 20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION en 05 3: o CD ^ 2 d ^3 cu o" ^ '> CL> o a CX ( 8 o III I uJ I I p | Q) c4 o Hi <*> .TS 2- .2 03 - 2 11 S HI 11 05 ff) ^_j ligl > ti|' 2:; BULLETIN 346] ALMOND POLLINATION 21 en ) vO 2 ^ \ <[ -2 >- C to B v O J5 a . - S 3 3 - x = CJ i!J xxxxx xxxxx iJ 22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION King. The King may be successfully polleiiized with the Ne Plus Ultra and Nonpareil varieties. Klondike. The Ne Plus Ultra may be used to pollenize the Klon- dike. Lwnguedoc. Of the nine sorts of pollen used to cross with the Languedoc, that of the California, Drake, and Eureka varieties yielded the best results. The Texas is the only variety which failed to set fruit on the Languedoc. From the standpoint of the blooming season the Drake should probably be recommended as a pollenizer. Levelling. The I. X. L., Ne Plus Ultra, and Nonpareil may be recommended as pollenizers for the Lewelling. Ne Plus Ultra. Of the nine varieties of pollen used to cross with the Ne Plus Ultra, the following gave the best results : I. X. L., Jordan, Nonpareil. From a commercial standpoint the I. X. L. and Nonpareil should be given preference. Nonpareil. Of the eleven varieties tested as pollenizers for the Nonpareil only the I. X. L. failed to set fruit. The following varieties proved to be successful pollenizers : California, Drake, Eureka, Languedoc, Ne Plus Ultra, Peerless, and Texas. Preference should be given to the California, Drake, Ne Plus Ultra, and Texas. Peerless. Of the nine varieties used as pollenizers for the Peerless, the Drake, Languedoc, and Texas proved to be the best. Princess. The Nonpareil and Ne Plus Ultra may be used to pollen- ize the Princess. Reams. California, I. X. L., Ne Plus Ultra, Nonpareil, Texas, and Drake gave entirely satisfactory results as pollenizers for the Reams. The Texas should be given preference. Sellers. The Nonpareil is a satisfactory pollenizer for the Sellers. Silver Shell. The Drake may be recommended as a pollenizer for the Silver Shell. Texas. The following varieties may be used to pollenize the Texas : Drake, Eureka, I. X. L., Ne Plus Ultra, Nonpareil, and Reams. From the standpoint of the blooming season, preference should be given to the Reams, Drake, and Eureka. The Languedoc failed to set any fruit on the Texas. POLLENIZING AGENCIES After having planted inter-fertile varieties the orchardist should, by all means, provide an agency for the transfer of the pollen from* the trees of one variety to those of another. The common honey bee is by far the best carrier of pollen and it will pay the grower to keep bees although he may not care to go into the honey business. Bees, BULLETIN 346] ALMOND POLLINATION 23 however, are a very profitable side line for the orchardist, especially if alfalfa fields are available after the blooming season of fruit has passed. About one hive of bees to an acre of bearing orchard should be provided. Preferably the hives should be scattered as widely as possible throughout the orchard during the blooming season. Experi- ments and experience have shown that little reliance can be placed on the efficacy of wind and insects, other than the honey bee, in effecting the transfer of pollen from tree to tree, or, indeed, from flower to flower. Eliminating from consideration all conditions which may influence the f ruitfulness of an orchard except those occurring at blooming time, it may be said that the set is largely influenced by weather conditions at time of blooming. Cold weather, aside from killing the blossoms or lowering the vitality of the pollen, often prevents bees from work- ing. The same would be true if cloudy, wet, and windy weather prevail. For their best work bees demand clear, warm, and quiet days and since the weather at the time almonds bloom is often quite unsettled, it is readily seen that the blooming period of the various pollenizing varieties should overlap perhaps a week in order that there may be one or two days at least when the weather will be favor- able for insect pollination. As a case in point mention may be made of the 1917 blooming season of almonds. Many almond growers had, during that season, a light crop due not to lack of proper varieties, nor to freezing cold, but to the existence of unfavorable weather conditions throughout the blooming period so that the bees were prevented from working. This point further illustrates the necessity of having in the orchard a large number of these " helpers." ARRANGEMENT OF THE ORCHARD FROM A POLLINATION STANDPOINT In planting an orchard it is desirable to have at least every sixth and preferably every fourth row of a pollenizing variety. For con- venience in harvesting, it is best to plant two rows of one kind, then two rows of the pollenizing variety, and so on ; or, if it is desired to have more of one variety than another, four rows of the favored variety and then two rows of the pollenizer, and repeat. For various reasons, it is often desirable to reduce the number of pollenizing trees to the minimum. Under these circumstances, one tree in twenty-five is perhaps sufficient, although at least one tree in eight is strongly recommended. It is seldom wise to graft over a part of a tree to the pollenizing variety as this tends toward confusion and expense in harvesting. 24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION In planting one tree of the pollenizer to seven or eight of the main variety, the pollenizer should be placed as every third tree in every third row in such a way that the spaces in the pollination rows are broken, as shown in diagram below, the ' ' " in each case representing a pollenizer tree. If by chance a self -sterile variety has been planted in a solid block, the necessary pollinator may be introduced by grafting. Some relief may be obtained during the years while waiting for the trees grafted over to pollenizing varieties to come into bearing, by cutting off large limbs of pollenizing varieties, placing the cut ends in buckets of water and distributing them throughout the orchard during the blooming period. Such limbs will live for several days and continue to bloom, forming pollen for the bees to transfer to the self-sterile variety. SUMMARY OF ALMOND POLLINATION 1. Almond varieties may be roughly divided into two classes, early bloomers and late bloomers, when the length of their effective full bloom is considered. 2. The first blossoms produced by most almond varieties each season may yield a smaller amount of pollen and pollen which is inferior in viability to that produced by flowers on the same tree maturing several days or a week later. 3. Pollenizing agencies, such as the honey bee, are necessary to the set of a good crop of fruit. One colony of honey bees should be provided for each acre of orchard. BULLETIN 346] ALMOND POLLJNATION 25 4. All almond varieties thus far tested have proved self-sterile, at least in certain years. All of the twenty varieties tested during the seasons of 1917 and 1919 proved self-sterile. This list includes the Big White Flat, California, Drake, Eureka, Golden State, Harriott, I. X. L., Jordan, King, Klondike, Languedoc, Lewelling, Ne Plus Ultra, Nonpareil, Peerless, Princess, Sellers, Silver Shell, Reams, Texas, and a hardshell seedling. 5. The I. X. L. and Nonpareil varieties proved practically inter- sterile during three seasons' work. 6. The Languedoc and Texas proved practically inter-sterile as shown by the results of 1917 and 1919. 7. The California, disregarding its own commercial value, at pres- ent seems to be the one best pollenizer for all varieties thus far tested, which have a coincident period of bloom. 8. The Big White Flat may be pollinated by the Harriott. The California may be pollinated by the Nonpareil and Drake. The Drake may be pollinated by the California, Ne Plus Ultra, Nonpareil, and Texas. The Eureka may be pollinated by the Nonpareil and Drake. The Golden State may be pollinated by the Drake and Nonpareil. The Harriott may be pollinated by the Ne Plus Ultra. The L X. L. may be pollinated by the Ne Plus Ultra. The Jordan may be pollinated by the I. X. L. and Nonpareil. The King may be pollinated by the Ne Plus Ultra and Non- pareil. The Klondike may be pollinated by the Ne Plus Ultra. The Languedoc may be pollinated by the Drake. The Lewelling may be pollinated by the I. X. L., Ne Plus Ultra, and Nonpareil. The Ne Plus Ultra may be pollinated by the California, I. X. L., Jordan, and Nonpareil. The Nonpareil may be pollinated by the California, Drake, Jor- dan, Ne Plus Ultra, Peerless, and Texas. The Peerless may be pollinated by the Drake, Languedoc, and Texas. The Princess may be pollinated by the Ne Plus Ultra and Non- pareil. The Reams may be pollinated by the Texas. The Sellers may be pollinated by the Drake and Nonpareil. 26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The Silver Shell may be pollinated by the Drake. The Texas may be pollinated by the Drake and Nonpareil. 9. Care should be taken in the arrangement of varieties in the orchard to facilitate cross-pollination and convenience in harvesting. ACKNOWLEDGMENTS The writers wish to express their appreciation of the assistance they received from students and colleagues. Messrs. M. B. Weidenthal and Henry Schlapp, senior students in the University of California, performed certain phases of the work as thesis problems, and without their help it would have been impossible to make so many pollinations. Mr. M. N. Wood, Miss Edna Russ, and Miss R. M. Amesbury, mem- bers of the Division of Pomology, also rendered invaluable assistance in the field and laboratory. Mr. W. L. Howard has given great service in suggestions and criticisms. Mr. George W. Pierce and Mr. G. W. Atterbury kindly allowed the use of their orchards for certain experi- ments which could not be carried out in the University orchards. BULLETIN 346] ALMOND POLLINATION 27 Fig. 7. Only two Nonpareil fruits from 349 blossoms left open to natural conditions (normal set). Only that portion of the branch bearing fruit is shown in the photograph. A typical example of the normal set in the Pierce orchard, 1918. 28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 8. No fruit set on branch of Nonpareil which was pollinated with its own pollen. Twenty-eight blossoms set no fruit. A typical cluster of Nonpareil when self -pollinated. Pierce orchard, 1918. BULLETIN 346] ALMOND POLLINATION 29 Fig. 9. Six Nonpareil fruits set from fifteen blossoms pollinated with Califor- nia pollen. A typical cluster resulting from crossing Nonpareil with California. Pierce orchard, 1918. 30 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 10. Twelve Nonpareil fruits set from thirty-one blossoms pollinated with Golden State pollen. A typical cluster resulting from crossing Nonpareil with Golden State. Pierce orchard, 1918. BULLETIN 346] ALMOND POLLINATION 31 , Fig. 11. No fruits set on branch of Nonpareil which was pollinated with I. X. L. pollen. Fifteen blossoms set no fruit. A typical cluster resulting from crossing Nonpareil with I. X. L. Pierce orchard, 1918. 32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 12. Fifteen Nonpareil fruits set from twenty-eight blossoms pollinated with Languedoe pollen. A typical cluster resulting from crossing Nonpareil with Languedoc. Pierce orchard, 1918. BULLETIN 34(5] ALMOND POLLINATION 33 Fig. 13. Fourteen Nonpareil fruits set from twenty-nine blossoms pollinated with Ne Plus Ultra pollen. A typical cluster resulting from crossing Nonpareil with Ne Plus Ultra. Pierce orchard, 1918. 34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 14. Nine Nonpareil fruits set from twenty blossoms pollinated with Peerless pollen. A typical cluster resulting from crossing Nonpareil with Peerless. Pierce orchard, 1918. BULLETIN 346] ALMOND POLLINATION Fig. 15. Twelve Nonpareil fruits set from twenty-nine blossoms pollinated with Texas pollen. A typical cluster resulting from crossing Nonpareil with Texas. Pierce orchard, 1918. 35378 UNIVERSITY OF CALIFORNIA AT LOS ANGELES THE UNIVERSITY LIBRARY This book is DUE on the last date stamped below JAN* 3 19& 2 4 MAY 1819 WIHl MAY 1 1968 Form L-9-15m-7,'35 / r UNIVERSITY of CALIFORNIA AT LOS ANGELES LIBRARY