UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA THE SEEDLESS RAISIN GRAPES BY FREDERIC T. BIOLETTI BULLETIN No. 298 (September, 1918) Revised May, 1921 UNIVERSITY OF CALIFORNIA PRESS BERKELEY, CALIFORNIA David P. Barrows, President of the University. EXPERIMENT STATION STAFF HEADS OF DIVISIONS Thomas Forsyth Hunt, Dean. Edward J. Wickson, Horticulture (Emeritus). Walter Mulford, Forestry, Director of Resident Instruction. C. M. Haring, Veterinary Science, Director of Agricultural Experiment Station. B. H. Crocheron, Director of Agricultural Extension. Hubert E. Van Norman, Vice-Director; Dairy Management. James T. Barrett, Acting Director of Citrus Experiment Station ; Plant Pathology. 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. John S. Burd, Agricultural Chemistry. Charles B. Lipman, Soil Chemistry and Bacteriology. Ernest B. Babcock, Genetics. Gordon H. True, Animal Husbandry. 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. J. C. Whitten, Pomology. fFRANK Adams, Irrigation Investigations. C. L. Eoadhouse, Dairy Industry. F. L. Griffin, Agricultural Education. John E. Dougherty, Poultry Husbandry. W. B. Herms, Entomology and Parasitology. L. J. Fletcher, Agricultural Engineering. Edwin C. Voorhies, Assistant to the Dean. division of viticulture and fruit products Frederic T. Bioletti W. V. Cruess L. O. Bonnett A. W. Christie G. Barovetto t In cooperation with Office of Public Roads and Rural Engineering, TJ. S. Department of Agriculture. THE SEEDLESS RAISIN GRAPES By FREDERIC T. BIOLETTI INTRODUCTION Types of Baisins. — The raisins of the world are of four main types: (1) of large size, made principally from the Muscat of Alex- andria grape and known generally as Muscat or Malaga raisins; (2) of medium size, light colored and seedless, made principally from the Sultanina grape and known generally as Sultana raisins; (3) of small size, dark colored and seedless, made principally from the Black Corinth grape and known in English as Currants; (4) of various sizes, colors, and qualities, and made from almost any vinifera varieties, and usually known as Dried Grapes. The last are not generally classified as raisins. There are numerous subdivisions and modifications of these types. This bulletin deals with the second and the third types. Statistics. — The principal raisin-producing countries of the world are Greece, California, Turkey, Spain, and Australia. Their com- parative importance is shown by the following figures: 1 World's Production of Baisins in 1913 Per cent Principal types Country Tons of total Muscats and Sultanas California 65,000 22 Currants Greece 180,000 60 Sultanas Turkey 23,000 8 Muscats Spain 20,000 7 Muscats and Currants Australia 14,000 5 The California crop increased from 40,000 to 128,000 tons (220 per cent) between 1904 and 1915. During the same period, the crop of Australia increased 136 per cent, while that of Spain decreased 26 per cent. Those of Turkey and Greece were practically stationary. In 1916, California produced about one half the raisins of the world. Kinds of Baisins in California. — The raisin crop of California in 1916 was as follows : Muscats 89,000 tons = 67.4% f Thompson's 23,500 tons *Sultanas \ Sultanas, seedless 7,000 tons [Bleached 7,000 tons 37,500 tonsrr: 28.4% Dried Grapes 5,500 tons = 4.2% Total 132,000 tons =100.0% *These include the dried Sultanina (Thompson) and Sultana grapes. i All statistics are quoted or calculated from those given by George Robertson in the Statistical Report of the California State Board of Agriculture for 1916. 4 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Comparison of Muscat and Seedless Eaisin Crops in California Muscats Sultanas I \ I \ Year Tons Per cent Tons Per cent 1913 49,294 76.3 15,322 23.7 1914 60,000 69.0 27,000 31.0 1915 78,123 82.0 17,260 18.0 1916 89,000 70.4 37,500 29.6 Mean ratio, 74.4 Mean ratio, 25.6 There is no confirmation here of the commonly expressed opinion that the crop of seedless raisins has been increasing much more rapidly than that of the Muscat raisins. Approximately one quarter of the total crop is of Sultana type and three quarters of Muscat type. Probably the influence of the large plantings of Sultanina which have undoubtedly been made during recent years will be evident in future crops. VARIETIES Most of the seedless raisins of commerce are made from two varieties — the Sultanina and the Black Corinth. The Sultana and the White Corinth make raisins of similar type, but are much less exten- sively grown. The Black Monukka is said to be the favorite raisin grape of Persia and is beginning to be dried in California. The Rose Sultanina is used principally as a table grape. Seedless raisins of a type peculiar to California are also made from the abortive seedless berries ("shot grapes") which occur commonly on the Muscat of Alexandria and which are separated in the cleaning and grading of Muscat raisins. The various seedless grapes and their uses are shown in the follow- ing table : Seedless Grapes and Their Uses Name of grape: Use: Sultanina Sultanas of commerce Sultanina, Eose Table grape Sultanina, Giant Curiosity of collections Sultana Inferior Sultanas of commerce Black Corinth Currants White Corinth Inferior currants Black Monukka Table grape and raisins Muscat ("shot grapes") Seedless muscats Sultanina. — Synonyms: Thompson, Thompson's Seedless (in Cali- fornia), Lady de Coverly (English hothouses), Sultanieh, Oval-fruited Kishmish (Turkey, Palestine). This variety is grown in collections Bulletin 298 TIIE SEEDLESS RAISIN GRAPES 5 or in small quantities as a table grape throughout the Mediterranean region. It is grown largely in the Levants, more particularly in the warmer parts of Asia Minor, as a raisin grape. It appears to be widely distributed in Asia as far east as Persia and probably beyond. From it are made the genuine Sultana raisins of Smyrna. It was brought to California in 1872 by Wm. Thompon, Sr., of Sutter County, who obtained it from Ellwanger and Barry, of Rochester, New York, under the name of Lady de Coverley, a name by which it is known in English hothouses. It was distributed here under the name of Thompson's Seedless to distinguish it from the Seedless Sultana, a grape grown more sparingly in the same Asiatic regions. Its name of Sultanina, by which it is known in most countries, or Sultanieh, as it is sometimes spelled, a name derived from the town of Soultanieh, in Persia. Mr. Thompson deserves great credit for having introduced this valuable grape into California, but it seems hardly necessary or desir- able to change the euphonious and appropriate name by which it has been known in most of the regions where it has been grown probably for hundreds of years. The vine is remarkably vigorous, producing in rich soil canes often thirty feet long. These canes are often comparatively thin and slightly flattened for a foot or so near the trunk and become rounded and much thicker in their middle portion. The joints are very long, and strong laterals are produced abundantly, especially when the growing shoots are pinched or topped. The bunches are very large, conical, and usually well filled. The berries are oval, yellow, and small to under medium in size. They are perfectly seedless, without marked flavor, and low in acidity. Rose Sultanina. — Synonym: Sultanina Rosea. This is a mere color variation of the last, with which it is identical in all respects but the color of the fruit. It was imported from Italy by the United States Department of Agriculture in 1900. It is numbered 5616 (3921) in the list of plant introductions published by the Department. It is known in European vine collections and appears to have been brought to Europe from some part of Anatolia (Asia Minor). Raisins have been made from it, but they are inferior in color to those made from the ordinary or white Sultanina. As a table grape, it is very attractive when it attains its full, bright rose color. In the hotter regions of the state, as Imperial, Fresno, and Yolo counties, it remains white or only faintly pink and is less attractive in appear- ance than the ordinary form. It develops a most brilliant color in 6 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION Sonoma County and probably would do so in any of the cooler grape- growing regions. Giant Sultanina. — Occasionally, a vine of Sultanina is found show- ing a remarkable hypertrophy of all its parts. The berries are round and nearly as large as those of Muscat. The peduncles, canes, joints, pith, and leaves also show this enlargement. Vines obtained by graft- ing or rooting cuttings from this form retain its peculiarities. The vine is evidently a bud sport showing the characteristics of what the biologists call "gigantism." Mr. L. F. Arnold, near Merced, found a branch of this form growing on the trunk of an ordinary Sultanina. This proves its nature of a bud sport and indicates that the specimens found in various parts of California may have had several independent origins. If this is the case a careful search among the various forms might result in the discovery of a type free from the defects noted below. If this could be done, the large size of the berry would be of great value. It is possible that this vine has given rise to the legend of a seedless Muscat. It has, however, none of the flavor or other characteristics of the Muscat and, in fact, in spite of its marked peculiarities, no one familiar with varieties of vines would fail to recognize it as a form of the Sultanina. It is now growing at the experiment vineyard at Davis, but the crops so far have been small and irregular. It appears to lack vigor and is somewhat difficult to propagate. Similar cases of gigantism have been noted with Muscat of Alex- andria, Flame Tokay, and Zinfandel. It seems probable that it is a variation similar to that of the Nectarine and that it may occur with any variety. All the varieties in which it has been noted are grown in large quantities, which increases the chance of finding a very rare variation. Sultana. — Synonyms: Seedless Sultana (in California), round- berried Kishmish (French ampelographies). This grape was intro- duced very early into California by Mr. West, a Stockton nurseryman. Under the mistaken impression that it was the variety from which the Sultana raisins of commerce were made, it was distributed under this name. This is unfortunate, as the name became fixed in popular use here before the Sultanina, the real variety producing Sultana raisins, was introduced. The grape seems to have been introduced into Europe from Asiatic Turkey. In Turkish, any seedless grape or raisin is called Kishmish and two varieties are recognized, the "round-fruited," which we call the Sultana, and the ' ' oval-fruited, ' ' which is the true Sultanina, and which we call the Thompson. Bulletin 298 TnE SEEDLESS RAISIN GRAPES 7 The vine resembles the Sultanina in its vigor and general aspect. It is a little less riotous in its growth and a little more inclined to be fruitful, even with defective pruning. The bunches are very large, compact, and of a very characteristic shape. The central part is remarkably long and perfectly cylindrical, and the upper part very heavily shouldered. The berries are wider than they are long and slightly flattened at the apex. In flavor and color, they resemble the Sultanina, but are inclined to have a higher acidity. A seed is found in an occasional berry. Black Corinth. — Synonyms: Zante Currant, Panariti( ?), Passerina nera (in Italy). This variety was early introduced into California and planted in various places in the Sacramento and San Joaquin valleys. Later introductions by the United States Department of Agriculture were widely distributed. Unlike the Sultanina, it was never largely planted as no one until lately has been able to make it produce paying crops. By severe annual ringings of the main trunk, it has been made to produce satisfactorily in Australia, and fair crops have been obtained in the University experiment vineyards by grafting it on resistant stocks. The vine is of great vigor and the trunk will grow a hundred or more feet in length if given the opportunity. Under some conditions, apparently when it is allowed to grow to very large size, many or most of its berries grow large and develop seeds. In such cases, it is of no value as a raisin grape. It is from this variety that the so-called Zante or Greek currants are made. The bunches are of medium size, compact and cylindrical, with well-marked shoulders and sometimes winged. The berries are very small, no larger than elderberries, reddish black, round, and seedless. Occasionally a berry containing seeds is found. White Corinth. — Synonym: Passerina bianca (in Italy). This variety resembles the last one in many of its characteristics. It is, however, more easily made to bear good crops, and several small vine- yards of this variety have been in existence in the Sacramento Valley for many years. It will boar on its own roots and with the same treat- ment that succeeds with the Sultanina. The vine is nearly as vigorous as the Black Corinth, the leaves are a little lighter in color, and the fruit is white. The bunches are medium or a little larger than those of the Black and more conical in shape. The berries are a little larger, intermediate in size between the Black Corinth and the Sultana. They are rounded and slightly flat- tened like the latter variety. They lack the flavor and acidity of the black. "When dried, they make an excellent currant, but not equal O UNIVERSITY OF CALIFORNIA EXPERIMENT STATION to those from the Black. The dried fruit is intermediate between a currant and a Sultana and, though intrinsically of good quality, it must be marketed as a second-grade currant or Sultana. Red Corinth. — Synonym: Passerina rosa (in Italy). This variety does not seem to have been introduced into California. Some vines called by this name are simply Black Corinth that, owing to peculiarities of local soil or climate, do not develop their full color. Black Monukka. — This is the most promising grape which has been introduced into California for many years. It has been marketed successfully as a table, a shipping, and a raisin grape. The vine is even more vigorous than the Sultanina. It develops quickly and comes into bearing early, and bears well with short or long pruning. When cane-pruned it has a tendency to overbear. It is probably best suited to cordon pruning with spurs. The bunches are large, conical, shouldered and well-filled. The berries are larger than those of the Sultanina and ripen several days earlier. They are elongated, purplish black with firm pulp and pleas- ing though neutral flavor. They are practically seedless for, while abortive seeds occur in most of the berries, these are soft and not noticeable in eating. The raisins are of excellent appearance, texture, and flavor. They constitute a type of raisin entirely new to commerce, but judging by the reception they have met by the few consumers to whom they have been offered they should bave no difficulty in finding a market. The Monukka was sent to the United States Department of Agri- culture by the Reverend W. Wilts, of the Royal Horticultural Society of London. According to A. F. Barron, it came to England from India. It is probably the Munaqqa, a Persion raisin grape. Seedless Muscat. — There have been rumors for many years that a large seedless Muscat is grown in Chile, but no one has been able to obtain any for California. It is not likely that such a variety exists. A seedless grape is a defective grape, that is, one which bas not developed the physiologically essential part of the fruit, the seed, and this defect seems to be correlated with small size. The seedless Muscats are grapes which have been imperfectly pollenized and in some seasons they occur in large numbers on most of the bunches, but it is rare that they constitute all the berries of a bunch. This con- dition is called by French grape growers "millerandage" and by California grape growers "shot grapes." It occurs sometimes with nearly all varieties. Bulletin 298 THE SEEDLESS RAISIN GRAPES 9 LOCATION AND SOIL Location. — The present location of the vineyards of seedless raisin grapes is indicated by the returns of raisins in 1916 from tin; various counties : Distribution op Crop of Suitana Raisins* in 1916 Per cent of total crop Fresno County 73.2 Tulare County 10.8 Kings County 1.7 Merced County .4 Madera County .3 Kern County J Stanislaus County .1 San Joaquin Valley 86.6 Sutter County 10.5 Yolo County 2.7 Sacramento Valley 13.2 Southern California .2 100.00 Nearly nine tenths of the seedless raisins of California are pro- duced in the upper San Joaquin Valley, where the soil and climate are particularly suitable. The vines grow and bear as well in several other districts, but the conditions for raisin making are not quite so favorable. In the San Joaquin Valley, 62 per cent of the seedless grapes are Sultanina, in the Sacramento Valley, 84 per cent. In Yolo County, on the west side of the Sacramento River, only 20 per cent are Sultanina and the rest Sultana, while in Sutter County on the east side, the proportion of Sultanina is over 99 per cent. These differences are probably not due to any differences of adaptation of the two varieties to the various localities, but rather to accidental historical causes related to the first plantings. Both varieties sei m to do equally well in all these localities when given proper treatment. In southern California, the Sultana is grown almost exclusively as a seedless raisin grape. The Sultanina has not given such good results, perhaps owing to a lack of knowledge of how to prune it. In all the counties where seedless raisins are produced, and in other counties, some Sultanina grapes are shipped and marketed fresh as * Where the expression "Sultana raisins" occurs without qualification, it includes all of what are commonly known in California as "Thompson and Seedless Sultanas." 10 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION table grapes. Imperial County in particular ships a large quantity very early in the season. None of the other seedless grapes are grown in California in large commercial quantities. There have been a few small vineyards of White Corinth in Placer County for some years. The Black Corinth has been planted in several localities during the last few years, but usually not in large quantities. The Black Monukka is attracting much attention and for the last two seasons all cuttings that could be procured have been planted. The total present area covered by all three, however, is probably below 1000 acres. Any of the seedless grapes will grow and ripen their fruit in almost any of the grape-growing districts of California, but they bear better in the warmer parts. For raisin making, they must be grown in districts where they ripen early, before the usual arrival of autumn rains. This has so far confined raisin production to the interior valleys and southern California. The early ripening of the Black Corinth and of the Black Monukka may make it possible to extend the area of raisin production. The same effect may be expected from improvements in the construction of dehydrators. As a shipping table grape, only the Sultanina is grown extensively. Some more or less successful shipments of fresh Black Corinth have been made to eastern points where their peculiar appearance and small size have proved attractive. They are said to have been marketed as "California Huckelberries' and used for pies. The few eastern shipments which have been made of fresh Black Monukka have suc- ceeded so well that there seems a strong probability that this variety may be a successful rival of the Sultanina as an early table grape. Soils. — Owing to their great vigor, the Sultanina and Sultana will give paying crops on light sandy soils where most other varieties fail. They will give larger crops, however, on better soils and it is unsafe to plant them where the crops are likely to be less than the average. While prices are high, such crops may be profitable, but when prices fall they cannot compete with heavier crops from better soil. The adaptation of the Corinth grapes is not well known. It is probably similar to that of the Sultanina. The Black Monukka has grown vigorously and borne well in practically all cases where it has been tried. It has succeeded under extremes of climate ranging from that of Contra Costa County to that of Imperial and in soils ranging from heavy black adobe to sandy loam. Bulletin 298 THE seedless raisin GRAPES 11 PLANTING THE VINEYARD Preparation of the Ground. — The best results can be obtained with vines only if the ground is properly prepared before planting. It should be cleared of stumps and rocks, properly graded, especially where irrigation is to be practiced, and plowed as deep as is prac- ticable, at least ten inches. Any troublesome weeds, such as Morning Glory, Johnson grass, or Bermuda grass should be eradicated before planting. Hardpan within three feet should be blasted at every point where a vine is to be planted. A few years as an alfalfa field is an excellent preparation. In irrigated districts, a crop of cow-peas or similar leguminous crop grown in the summer and plowed in deep during the autumn prepares the soil perfectly for planting during the following spring. Planting Stock. — For planting, cuttings, rooted vines, or bench- grafts may be used. Cuttings are almost as good as rooted vines if they can be made to grow during the first year. The Sultanina, however, is rather hard to root and many usually fail during the first year. The result is that much replanting is necessary, the vines are uneven in size, the vineyard is slower coming to full bearing, and the cost in the end may be as large or larger than when rooted vines are used. The best cuttings are those of medium size with fairly close joints. "Well-grown laterals of the Sultanina often make the best cuttings. The other varieties root more easily, especially the Black Monukka. In most cases, it is best to use one-year-old rooted vines of moderate size. If of good quality and properly handled, practically every one will grow the first year and a full crop may be obtained the third or fourth season following planting. In districts infested with phylloxera, bench-grafts on resistant stocks should be used. These are more expensive, but are the only known defense against the pest. The extra cost is in part counter- balanced by the fact that the vines on resistant stocks bear earlier and perhaps better than on their own roots. Many varieties of resistant stocks have been tested at Kearney and Davis. All have given good to very good results with the Sultanina and Sultana. The Corinths seem to be more difficult to please and the other varieties have not been very thoroughly tested. The Sultanina has done best at Davis on A. X R. No. 1 and 101-14. On these stocks it has borne more than when ungrafted. On all other stocks it has borne less, especially on St. George, where it has yielded only one half. At Kearney the best crops have been obtained on 1202, 12 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION 3306, and 3309, but all stocks have done well, though St. George is near the bottom of the list. The Sultana has given the best crops on 41-B, 420-A, and A. X R- No. 1 and 1202. St. George has a fair record with this variety at Kearney but a poor record at Davis. The Black Corinth has yielded most on 41-B, Riparia gloire, and 3306. It has done poorly on St. George and has failed entirely on 420-A. The White Corinth has given the best results on 3306. Laying out the Vineyard. — In laying out the vineyard, two points have to be determined: (1) the area to be given to each vine, and (2) the arrangement of the vines. As all seedless vines are vigorous growers, they require abundant room. If crowded, they may give a little more in the first one or two crops, but the yield will be less later and the cost of handling greater. The appropriate space for each vine will vary from about seventy square feet to about a hundred and thirty, according to the variety and the soil. The Sultana may be planted a little closer than the others without injury. In rich, deep soil where the vines will be exceptionally vigorous, they must be given more room; in sandy, shallow, or poor soil, they should be placed closer. As all these varieties require long pruning and trellising, the vineyard should be laid out on the avenue system. The following table gives the arrangements and distances which are recommended: Arrangement and Distances for Seedless Vines Rich Soil Poor Soil* < * 1 , • 1 Distances, Area, Vines, Distances Area, Vines, Variety feet square feet per acre feet square feet per acre Sultana 14x6 84 518 12x6 72 605 Sultanina 14x7 98 444 12x6 72 605 Corinth 14x7 98 444 12x6 72 605 Black Monukka 16x8 128 340 14x6 84 518 Intermediate distances may be adopted for intermediate cases. The distance apart of the vines in the row should in no case be less than six feet, as this is the minimum that will give room for the necessary three and four-foot fruit canes. The rows should in no case be nearer than twelve feet, as this is the minimum that will allow of inexpensive and efficient cultivation. It is better to err on the side of wide planting than of narrow, for there is no practical limit to the size these vines can be made to grow except the difficulty of supporting them; a large vine will bear at least as much as two vines of half the size and will be less costly to prune and cultivate. * The word "poor" is used relatively. An infertile soil should not be used for vines of any kind. Bulletin 298 T ] IE SEEDLESS RAISIN GRAPES 13 COST AND RETURNS* It may be estimated roughly that the expenses of a vineyard of seedless raisin grapes, Sultanina, Sultana, or Corinth, properly managed will amount, on the average, to about $95 per acre. This includes vineyard work, drying and delivering the crop, water, taxes, depreciation, and 6 per cent interest on an investment of $350 per acre, and is based on a crop of V/2 tons of raisins, which is about the average. This indicates that a price of 3 cents per pound will just cover the expenses of the average vineyard and allow 6 per eenl interest on a moderate valuation of the property. It allows nothing for superintendence. A price of 5 cents per pound for the raisins would yield a profit of $55 per acre and a crop of three tons a profit of $60. If both price and crop were increased in these proportions, the profit would be $180 per acre. These calculations are based on the following estimates : Estimated Cost op a Vineyard of Seedless Grape Vines (Good level land, irrigation^ resistant vines, trellis) Land $200.00 Bench grafts (500) 30.00 Preparation of land 15.00 Planting 10.00 Cultivating 5.00 Interest and taxes 15.00 Cost the first year $275.00 Pruning $3.00 Staking 10.00 Replanting 5.00 Cultivation 5.00 Hand work 10.00 Interest and taxes 22.00 Cost the second year 55.00 Pruning $5.00 Cultivation 5.00 Hand work 10.00 Trellising 55.00 Interest and taxes 25.00 Gross cost, third year $100.00 Crop, one ton at 4 cents net 80.00 Net cost, third year 20.00 Total cost $350.00 * These estimates were made in 1918. They can be modified for changes in cost of labor and material. t The cost of irrigation is not included, as it varies too widely. It will range from $2.50 to $15.00 per acre per year. 14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Estimated Cost-of Sultanina Vineyard (Valuation of $350) Annual cost of maintenance: Pruning and tying $12.50 Plowing and cultivating 7.50 Hand work 10.00 Vineyard work $30.00 Interest and taxes $28.00 Depreciation 10.00 Cost $85.50 Net returns $14.50 94.25 55.75 103.00 97.00 111.75 138.25 120.50 179.50 Fixed charges 38.00 Total $68.00 Harvesting, drying, and hauling raisins, per ton 17.50 Profit per Acre at Five Cents per Pound Crop, Gross pounds returns 2,000 $100.00 3,000 150.00 4,000 200.00 5,000 250.00 6,000 300.00 Although these estimates are based on actual accounts and returns from vineyards, they must be considered as simply indicating the probabilities. The investment, the cost of maintenance, the cost of drying, the amount and price of the crop, will all vary within wide limits. Those given must be considered only as average figures and they refer more particularly to the Fresno region. As iy 2 tons per acre is the average crop of Sultanina vineyards in California, this indicates that at 5 cents per pound for the raisins the vineyards are fairly profitable. Many vineyards produce less than a ton and cannot be considered profitable. Others produce two tons and are very profitable. Sultana vineyards are, on the whole, a little more productive, but the price of the raisins is somewhat lower. There is little accurate information on the yield of the Corinth grapes in commercial vineyards. The White Corinth yields fairly well on its own roots, but the Black yields very little unless subjected to the operation of girdling or ringing. This consists of removing a narrow ring of bark from the trunk near the surface of the ground. This must be done every year about the time of blossoming, preferably a little after. On suitable resistant stocks the Black Corinth gives good crops at first without girdling, but later requires the operation as much as when growing on its own roots. An idea of the possibilities of crop in good soil and with proper care is given by the following records of the experimental vineyards at Kearney and Davis. Bulletin 298 THE SEEDLESS RAISIN GKAPES 15 Yields op Seedless ; Vines at the Experiment Vineyards (In pounds of raisins per acre) Number Age Variety Locality of vines of vines Year Crop Sultanina Davis 192 5 1915 2,500 Sultanina Davis 144 6 1916 5,5 1'6 Sultanina Davis 240 7 1917 2,632 Sultanina, grafted Kearney 32 3 1914 4,172 Sultanina, grafted Kearney 98 3-4 1915 5,252 Sultanina, grafted Kearney 82 4-5 1916 8,366 Sultanina, grafted Kearney 83 5-6 1917 6,414 Sultana Davis 38 3 1914 3,239 Sultana Davis 38 4 1915 3,800 Sultana Davis 38 5 1916 5,486 Sultana Davis 38 6 1917 6,840 Sultana, grafted Davis 75 5 1917 4,838 Sultana, grafted Kearney 56 4 1915 8,026 Sultana, grafted Kearney 82 5 1916 8,792 Sultana, grafted Kearney 67 6 1917 7,563 Black Corinth Davis 38 5 1914 723 Black Corinth Davis 38 6 1915 Black Corinth Davis 38 7 1916 167 Black Corinth Davis 38 8 1917 158 Black Corinth, grafted Davis 48 5 1915 308 Black Corinth, grafted Davis 48 6 1916 1,153 Black Corinth, grafted Davis 48 7 1917 1,608 Black Corinth, grafted Kearney 9 5 1916 3,178 Black Corinth, grafted Kearney 9 6 1917 2,301 White Corinth Davis 38 5 1914 1,245 White Corinth Davis 38 6 1915 827 White Corinth Davis 38 7 1916 2,727 White Corinth Davis 38 8 1917 1,733 White Corinth, grafted Davis 24 5 1915 192 White Corinth, grafted Davis 24 6 1916 2,968 White Corinth, grafted Davis 24 7 1917 1,251 White Corinth, grafted Kearney 14 5 1916 4,539 White Corinth, grafted Kearney 17 6 1917 1,817 Average Annual Crop op Seedless Raisins Number of Pounds years i per acre Sultanina, ungrafted Davis 3 3,549 Sultanina, grafted Kearney 4 6,051 Sultana, ungrafted Davis 4 4,839 Sultana grafted Davis 1 4,838 Sultana, grafted Kearney 3 8,127 Black Corinth, ungrafted Davis 4 262 Black Corinth, grafted Davis 3 1,023 Black Corinth, grafted Kearney 2 2,740 White Corinth, ungrafted Davis 4 1,633 White Corinth, grafted Davis 3 1.471 White Corinth, grafted Kearney 2 3,178