|Prunus subsp. var.||Plum|
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera (peaches, cherries, bird cherries, etc) in the shoots having a terminal bud and the side buds solitary (not clustered), the flowers being grouped 1-5 together on short stems, and the fruit having a groove running down one side, and a smooth stone.
Plums come in a wide variety of colours and sizes. Some are much firmer-fleshed than others and some have yellow, white, green or red flesh, with equally varying skin colour.
When it flowers in the early spring, a plum tree will be covered in blossom, and in a good year approximately 50% of the flowers will be pollinated and become plums. Flowering starts after 80 growing degree days.
If the weather is too dry the plums will not develop past a certain stage, but will fall from the tree while still tiny green buds, and if it is unseasonably wet or if the plums are not harvested as soon as they are ripe, the fruit may develop a fungal condition called brown rot. Brown rot is not toxic, and very small affected areas can be cut out of the fruit, but unless the rot is caught immediately the fruit will no longer be edible. Plum is used as a food plant by the larvae of some Lepidoptera including November Moth, Willow Beauty and Short-cloaked Moth.
Plum cultivars in use today include:
- Damson, or Damask Plum
- Greengage, or greengage plum (firm, green flesh and skin even when ripe)
- Mirabelle (a dark yellow plum predominantly grown in northeast France)
- Satsuma plum (firm red flesh with a red skin)
- Golden or yellowgage plum (like the greengage, but yellow)
The subgenus is divided into three sections:
- Sect. Prunus (Old World plums). Leaves in bud rolled inwards; flowers 1-3 together; fruit smooth, often wax-bloomed.
- Sect. Prunocerasus (New World plums). Leaves in bud folded inwards; flowers 3-5 together; fruit smooth, often wax-bloomed.
- Sect. Armeniaca (Apricots). Leaves in bud rolled inwards; flowers very short-stalked; fruit velvety. Treated as a distinct subgenus by some authors.
- Fruit trees
- Fruit tree forms
- Fruit tree propagation
- Pruning fruit trees
- Prune (fruit)
- Dietary Fiber
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|Standard Cyclopedia of Horticulture|
Plum. The tree and fruit of many species of Prunus. A few kinds are grown for the ornamental flowers and others for colored or variegated foliage. Prunes are cured dried plums. It is probably more difficult to give specific practical advice for the management of the plum than for any other common fruit, for the reason that it represents several distinct species which are not equally adapted to all parts of the country, and the same remarks will not apply to them all. There is no country in which the domesticated plum flora is so complex as in North America, for not only are the specific types of Europe and of Japan grown, but also species that are peculiar to this continent. In the northeastern states and on the Pacific slope the European or domestica types are the leading plums. In these same areas and also in the South and in parts of the mid-continental region, the Japanese plums also are now popular. In the cold North, in the great interior basin, and also in many parts of the South, various native types now constitute the leading cultivated plums. These native plums are developed from wild species of the country, and they are unknown in cultivation (except in botanical or amateur collections) in any other part of the world. These have been developed chiefly within fifty and sixty years, although a few varieties are older than this. For a history of this evolution, see Bailey, "Sketch of the Evolution of our Native Fruits;" also, as well as for culture and varieties of plums in general, Waugh, "Plums and Plum-Culture/' and Hedrick, "The Plums of New York." See Prunus.
The plums cultivated in North America may be arranged in the following groups: 1. Domestica or European types, Prunus domestica. Native to western Asia, comprising the common or old-time plums, such as Green Gage, Lombard, Brad- shaw, Yellow Egg, and the like. They are the leading plums from Lake Michigan eastward and north of the Ohio, and on the Pacific slope. Figs. 3068, 3069 are of this species. The Damsons (Fig. 3070) are small- fruited forms of this general species-type. Of late years, hardy races of Prunus domestica have been introduced from Russia. These have value for the colder parts of the plum-growing regions. Figs. 3071, 3072, show representative forms of the Russian type. 2. The Myrobalan or cherry-plum type, Prunus cerasifera. Native to southeastern Europe or southwestern Asia. The seedlings are much used for stocks upon which to bud plums; the species is also the parent of a few named varieties, as Golden Cherry; and DeCaradeuc and Marianna are either offshoots of it or hybrids between it and one of the native plums, probably hybrids. 3. Japanese types, Prunus salicina (P. triflora). Evidently native to China. The type seems to be generally adapted to the United States, and is of great value to both the South and North. This species first appeared in this country in 1870, having been introduced into California from Japan. For historical sketch, see Bulletin No. 62, Cornell Experiment Station (1894); also Bulletin No. 106 (1896); Hedrick, "The Plums of New York." Fig. 3073 shows one of these plums; also Fig. 3074, as to tree forms, which are very variable in the different pomological varieties. 4. The apricot or Simon plum, Prunus Simonii. Native to China. Widely disseminated in this country, but little grown except in parts of California. Introduced about 1881. 5. The americana types, Prunus americana. P. nigra (Figs. 3075, 3076), and P. mexicana. The common wild plum of the North, and extending westward to the Rocky Mountains and southward to the Gulf and Texas. Admirably adapted to climates too severe for the domestica plums, as the Plains and the upper Mississippi Valley. 6. The Wild Goose and Chickasaw types, Prunus hortulana, P. angustifolia, P. Munsoniana (Figs. 3076, 3077). A variable type of plums, comprising such kinds as Wild Goose, Wayland, Moreman, Miner, Golden Beauty, Newman, Caddo Chief, Lone Star, and many others. The species involved in this group are not yet clearly defined botanically, and what part the hybrid and intergradient forms play in the evolution of cultivated varieties is yet largely to be determined. In adaptability they range from Michigan to Texas, eastward and westward, but are essentially fruits of the great interior basin. 7. The Beach plum, Prunus maritima. Native to the coast from New Brunswick to Virginia. In cultivation, represented by the unimportant Bassett's American; also as an ornamental plant. 8. The Pacific Coast native plum, Prunus subcordata, wild in California and Oregon. Sparingly brought into cultivation, chiefly in the form Known as the Sisson plum. The welding of these many stocks will undoubtedly produce a wide range of fruits in the future, of which we yet see only the first promise. The experiments of Hansen in South Dakota in hybridizing P. Simonii and P. americana, P. salicina and P. americana, P. Besseyi with plums, and others for a marginal climate, as well as the experiences of other workers in combining many of the species, all point to a wealth of plums for a continental area. The plum of history is Prunus domestica. It is to this species that general pomological literature applies. It gives us the prunes (see Prune). These plums may be thrown into five general groups, although any classification is arbitrary at certain points: 1. Prunes, characterized by sweet firm flesh, and capable of making a commercial dried product. They may be of any color, although blue-purple prunes are best known. Some of the prunes are grown in the East as ordinary market plums, being sold in the fresh state. Almost any plum can be made into dried prunes, but the varieties used commercially for this purpose constitute a more or less distinct class of sweet and thick- fleshed kinds (see definition, page 2719). In the East, prune is nothing more than a varietal name. 2. Damsons, comprising very small firm plums of various colors, usually borne in clusters, the leaves mostly small. The run-wild plums of old roadsides and farmyards are mostly of the general damson type (Fig. 3070). 3. The green gages, comprising various small green or yellow-green plums, of spherical form and mostly of high quality. Reine Claude is the commonestrepresentative of this group in the East. The name green gage often stands for a group rather than for a variety. 4. Large yellow plums, such as Coe Golden Drop, Washington, and the like. 5. Large colored plums, including the various red, blue, and purple varieties, like the blue prunes, Lombard, Bradshaw, Quackenboss, and the like. The Japanese plums (Prunus salicina) differ from the domesticas in having longer thinner smooth and mostly shining leaves, smooth twigs, a greater tendency to the production of lateral fruit-buds on the annual growth, and mostly rounder or shorter fruits with colors running more to cherry-reds and light yellows. Most of the varieties are as hardy as the domestica series. The Japanese varieties are important because they add variety to the list, and especially because they are rich in very early kinds, and the fruit is usually so firm that it carries well; aside from this, the trees are vigorous and very productive, and the species is less liable to injuries from black-knot and curculio than the domesticas.
The native plums, chiefly offspring of Prunus americana, P. nigra, P. angustifolia, P. Munsoniana, and P. hortulana represent a wide range of varieties. Those from Prunus americana and P. nigra parentage are very hardy and are adapted to regions in which the domestica and Japanese types are tender, as in northern New England, parts of Canada, and the northern plains states. Those partaking strongly of P. angustifolia parentage, and the greater part of the hortulanas, thrive well in the South, where the climate is too continuously hot for other plums or where the fruit-rot fungus is too prevalent.
The domestica varieties are mostly fertile with themselves, but the natives usually bear best in mixed planting so that pollination is assured. See Pollination. The Japanese varieties also usually profit by mixed plants ing. How far failure to set fruit is due in general to lack of pollination and how far to other causes, is yet largely to be worked out.
The plum thrives on a variety of soils. The domesticas commonly do best when planted in clay loam. They usually thrive well on lands which are suited to pears, or on the heavier lands to which apples are adapted. Yet many varieties grow well on lands that are comparatively light or even almost sandy, with good cafe. The americanas thrive best in a rather moist soil, and mulching is often very favorable to the size and quality of the fruit. The stocks upon which plums are grown are various. By far the greater number of the trees in the North are now grown on Myrobalan, which is a species of rather slow-growing plum (Prunus cerasifera), native to southeastern Europe and southwestern Asia. This is the stock sometimes recommended in the older fruit- books for the making of dwarf trees; but unless the top is kept well headed in, the trees generally make normal growth upon it. Trees grown on this root are usually larger and finer at one or two years of age than those grown on other plum stocks, and the probability is that they are nearly as useful from the grower's standpoint as any other. However, there are some varieties that overgrow the Myrobalan, and the stock is likely to sprout from the ground and thereby cause trouble. The Myrobalan is variable from seed, and this fact may account for some of the unsatisfactory results now and then reported. St. Julien is perhaps a better stock, but is more expensive to import and less readily budded. The Myrobalan and St. Julien stocks are imported. Probably the best stock for domesticas, from the standpoint of the grower, is the domestica itself, but seeds of it are more difficult to secure, the stock is more variable and it is more likely to be injured in the nursery row by leaf-fungi; therefore, as a matter of practice, the Myrobalan has very generally supplanted it. In the middle and southern states the peach is largely used as a stock upon which to grow plums, and it seems to be gaining favor in the North. It is undoubtedly a very excellent stock for sandy lands, and, in fact, is probably better for such lands than the Myrobalan itself. Some varieties—of which Lombard and French Damson are examples—do not take well on the peach. The Japanese plums are commonly worked on the peach. The Marianna stock, which is much recommended in the South, has not found favor in the North. Some varieties of plums are such slow and crooked growers in the nursery that it is advisable to top-graft or bud them on some strong and straight stock. The Lombard is no doubt the most adaptable stock for this purpose now grown by nurserymen. The old Union Purple is one of the best stocks, but is not much grown at present. Reine Claude, German Prune, and Copper are probably best when top-worked on some strong stock. For many native varieties, seedlings of vigorous natives, as of Golden Beauty and Wayland, make excellent stocks. Americanas should be worked on their own seedlings, at least in the North. In the South they are often budded on Marianna. The whole subject of plum stocks needs experimental study. on trees are usually planted when two years old the bud, although some of the strong-growing may be planted at a year old with the very best s. As a rule, all plum trees are planted about as part as are peaches, that is, from 15 to 20 feet way. Many growers prefer to plant them closer way than the other and eventually to stop cultin in one direction. If this system is used, they
may be placed 18 or 20 feet apart one way, and 8 to 12 feet the other way. When planted, the trees are pruned in essentially the same way as apple trees. It is usually advisable to start tops as low as possible and yet allow of the working of the curculio-catcher or other tools below them. This means that the limbs should start from 3 to 4 feet above the ground. With the modern implements and methods of tillage, there is little inconvenience in working the land if tops are started as low as this. The subsequent pruning of the plum tree has no special difficulties. About four or five main limbs are allowed to form the framework of the top, and in most varieties, especially those which are not very tall growers, the central trunk or leader may be allowed to remain. The fruit of the domesticas is borne mostly on spurs, as shown in Fig. 3078. These spurs, therefore, should not be removed unless it is desired to thin the fruit. In the americanas and the Japanese varieties, the fruit is borne both on spurs and on the annual axial growth.
Insects and diseases.—The black-knot is one of the most serious plum diseases. It is best kept in check by systematically cutting it out (several inches below the swelling) and burning it. The grower should go over his orchard for it in the summer and again as soon as the leaves fall. lf trees are thoroughly sprayed every year with self-boiled lime-sulfur or bordeaux mixture for the leaf-blight fungus, the black-knot will make .comparatively little headway in the orchard.
The blight, which causes the leaves to fall in August or September, is a damaging disease; but it can readily be kept in check by thorough spraying with self-boiled lime-sulfur or bordeaux mixture two or three times during the summer. The mixture for spraying plums should be weaker than for apples, particularly for the Japanese varieties.
The fruit-rot is the work of a fungus. Many times the dead and dried fruit may be seen hanging on the tree all winter, as shown in Fig. 3079; and in such cases it is very likely that the fruit-spur may be killed, as the upper one in the picture has been. In handling this disease, the first consideration is the fact that some varieties are much more susceptible to it than others. The Lombard is one of the worst. Again, if the fruit grows in dense clusters, the disease is more likely to be severe. The thinning of the fruit, therefore, is one of the best preventives of the spread of the disease, and at the same time, also, one of the most efficient means of increasing the size, quality, and salableness of the product. Thorough spraying with self-boiled lime-sulfur is a specific for the trouble and helpful in related troubles or diseases.
The curculio, which causes wormy fruit, can be held in check by the process described under Peach. Formerly, jarring the beetles on sheets or curculio- catchers (a wheelbarrow-like device with a large cloth hopper) was the prevailing practice with those who gave extra care to their fruit, and this method is still recommendable to amateurs and small plantations; but with the modern good tillage and the practice of keeping all parts of the plantation and the hedge-rows clean, and with the introduction of more effective spraying, the curculio is found to do much less damage and usually to be held sufficiently in check. Practising open pruning to let in the sun, and raking the dropped fruit out into the sun will also check the breeding. How far spraying with arsenicals will control the curculio on plums is not yet well understood, but growers usually feel that it is a distinct aid. To the bordeaux mixture or to self-boiled lime-sulfur, two and one-half pounds of arsenate of lead may be used to the fifty gallons, in one spraying soon after the petals drop, and another a week or ten days later. L. H. B.
Native American plums.
Approximately 300 varieties of plums, derived chiefly from six native types; have been named, described, and introduced by American nurserymen and have found their way into American orchards and American pomological literature. The major part of this interesting development came in response to the urgent demand, most manifest in the years from 1870 to 1900, for the discovery of new types of garden fruits suited to the peculiar conditions of the middle western prairie states. Outside this area, the native American plums made much less impression, and while they have been widely tried, they have been generally discarded. Even in tne area to which they are native and in which the need for them is greatest, they do not now play an exclusive role. A large part of the named varieties introduced by the nurserymen have already been lost to American horticulture. A creditable minority of these varieties, however, have qualities of absolute and considerable merit, and may be looked on as permanent additions to our pomological wealth. The native varieties are still propagated and planted by thousands annually, both for home use and for market. .For certain culinary purposes, many of the natives are superior; and in many places, particularly in states of middle latitude, they are the most profitable market plums grown.
The americana plums are especially qualified to withstand the severity of northern winters. They are superlatively hardy. They are practically the only plumsgrown in the cold northwestern states (except the comparatively unimportant nigras and the Miners) and their usefulness in northern New England and middle Canada is limited only by the extent to which they are known. Their cultivation has been developed to a special degree in Iowa, Wisconsin, Minnesota, and adjacent states. For this region they must be propagated always on americana stock. This stock has other advantages besides its hardiness, and it is coming into extensive use for all sorts of plums in the Northwest. The sand cherry is sometimes used as a stock, but has not yet passed the experimental stage. It dwarfs americana plums worked on it. It is perfectly hardy.
The americana plums are wayward and awkward growers. With many varieties it is impossible to make a comely orchard tree. They do not appear to take kindly to pruning ; and the usual method has been to let them very much alone. Careful pruning during the first few years, directed with a view to forming an open top on comparatively few supporting main branches, will do something toward shaping the trees; but with our present knowledge, no extensive pruning can be recommended for mature trees. The method of heading-in, as often practised with the domestica plums, is especially unadapted to the americanas.
The americana plums are early and very prolific bearers. Overbearing is a habit and a serious fault with most varieties. Extensive thinning of the fruit is indispensable. The trees are sometimes severely attacked by shot-hole fungus, and thorough spraying with bordeaux mixture or lime-sulfur is necessary. The fruit-rot (sclerotinia) attacks all the native plums more or less, and must be controlled by the usual remedies. See Diseases and Insects, Vol. II.
The nigra group has two or three important varieties of superor hardiness, as Cheney and Aitkin. In general, they bloom earlier and fruit less heavily than the americanas. Their habits and culture are the same.
The Miner-like varieties are hardly to be distinguished from the americanas in any way. They have practically the same geographical range, and may be given the same treatment in the orchard.
The hortulana group includes several varieties of great value, especially for the South. Of these, Wayland, Golden Beauty, Moreman, Benson, and Kanawha may be mentioned. They are not to be recommended generally for localities north of Massachusetts and Nebraska, their northern limit being determined less by their non-hardiness than by the very late ripening. This habit of late ripening, combined with very late blooming, makes them desirable for late marketing, particularly in southern markets. They are very prolific and constant bearers. The trees are free-growing, usually of rather spreading habit, and will bear heading-back better than the americanas. The pruning-knife, if used in season and with good judgment, will assist in making comparatively open-headed trees of these varieties.
The Wild Goose group (P. Munsoniana.) includes varieties like Wild Goose, Milton, Wooton, and Whitaker, specially adapted to the latitude of Maryland. Kentucky, and Kansas. They succeed only less well southward; but are not generally valuable to the north of this line. For the section named, the varieties of this class have unquestionably been the most profitable
plums grown up to the present time. They are propagated chiefly on peach, Marianna, and Myrobalan, but succeed even better on americana stocks. These stocks are all fairly satisfactory, though not equally good for all varieties; but, when peach stocks are used, the union should be made by whip-grafting on the peach root. Otherwise the peach stock comes above the ground and is a prey to the peach borer. The trees are mostly rapid willowy rather zigzag growers; and are amenable to the pruning-knife in about the same degree as the Wayland-like varieties already mentioned. Whitaker makes an open-headed tree without much trouble. So does Sophie. Wild Goose is more inclined to be thick and thorny in the top, but may be thinned carefully to make an accessible head. Milton is much like Wild Goose. Wooton makes a fine vase-form top, which, with a little timely pruning, is almost ideal. Wilder. James Vick, and some others, are prone to make thick bushy thorny tops, and are hard to manage. These varieties are all considerably subject to shot-hole fungus, which often strips them of their foliage in midsummer. They are mostly thin-skinned and liable to crack at ripening times, especially if the weather is wet. They should be picked rather green for shipment, the point to be observed being that they have attained their full size, rather than that they are dead ripe.
The Chickasaw varieties (P. angustifolia) are effective pollinizers for the Wild Goose and Japanese varieties blooming at same time; but very few of them have sufficient value in themselves to make them profitable orchard trees. A few varieties, like Munson and McCartney, are still planted for their own fruit; but in general they have been displaced by other types of plums. The trees are mostly bushy, thorny and thick- topped, sometimes so thick and thorny that the blackbirds can hardly get in to steal the fruit. It is difficult , to prune them enough to make really satisfactory trees. The Chickasaw plums are specially adapted to the southern states, though Pottawat- tamie (probably a form of Prunus Munsoniana) succeeds as far north as southern Iowa and central Vermont. They propagate readily on any kind of stocks, but are very much given to suckering wherever they make roots of their own.
Other types of native plums, such as the Sand plum, the Beach plum, the Pacific plum, and the like, are not sufficiently numerous in cultivation for their treatment to have been determined.
Hybrid plums of various strains have been introduced in considerable numbers. Most of these hybrid varieties resemble rather strongly one or the other of their parent species; and the best that can be said regarding their culture at this early day is that they may be safely treated like the varieties which they most closely resemble. Wickson, President, and perhaps Climax, with some others, resemble the Simon plum, and ought to have much the same treatment, that is, practically the same treatment as the Japanese varieties. Gonzales, Excelsior, Golden, and Juicy, on the other hand, resemble the Wild Goose type, and may have the same general treatment as Wild Goose. Some of these hybrid varieties, especially crosses of Wild Goose and Chickasaw types with the Japanese plums, are making some stand commercially, especially in the South, West, and in the Rocky Mountain States.
All the native plums, with wholly negligible exceptions, require cross-pollination. For the most part, however, they are fully inter-fertile, so that one given variety will pollinate any other variety, providing the two bloom at the same time. Simultaneous blooming is of chief importance in adjusting varieties to one another for cross-pollination. To determine which varieties bloom together, careful observations should be made in the orchard and recorded, or recourse must be had to the published tables. Pollination is effected chiefly, if not exclusively, by the bees, so that their presence should be encouraged.
Most, of the native plums make comparatively small trees, so that they may be set somewhat close together in orchard planting, say 12 to 20 feet apart, usually about 15 feet. Some varieties, particularly in the South, need 20 to 30 feet space. Putting a plum orchard down to grass is not admissible under any circumstances; but cultivation should cease with the first of July, or certainly by the middle of July; for the native plums are especially liable to make too much late summer growth. High manuring of the soil is not usually necessary, or even desirable; yet something considerably short of starvation will be found the best treatment for native plums.
F. A. WAUGH.
The plum in California.
The cultivation of the plum in California differs widely from that in the other plum-producing sections of the United States. Here the dreaded curculio is unknown, and while the equally dangerous black-knot has been found infesting a native wild cherry (P. demissa) it has never been observed in cultivated orchards. The most delicate varieties of the Old World find a very congenial home and form the basis of practically all orchard planting. In early mining days the California native plum (Prunus subcordata) was frequently cultivated, and before the introduction of European standard varieties attempts were made to improve the fruit by the usual methods of selection. Some very promising results were obtained; but since the demonstration of the great success of the more delicate and higher-flavored varieties, there has been little incentive to the use of the native species.
It seems hardly fair to make a distinction between "plums" and "prunes" in discussing this subject from the California standpoint. With the exception of the differences in the preparation for market, what may be said of the plum applies as well to the prune; for a prune is simply a plum which dries sweet without removing the pit. In most of the varieties of plums there occurs a fermentation around the pit in the process of drying, which prevente their being successfully dried without its removal; these are known as "plums." The prune varieties are, however, much richer in sugar which determines their adaptability to drying whole. As California has to find distant markets for most of its immense fruit crops, by far the greater portion of the plum areas are devoted to the production of prunes. The total amounts of plums produced in 1914 are as follows: Dried prunes, 51,000 tone; canned plums,
90,000 cases or 2,160,000 quarts; overland shipments, 7,906 carloads of fresh fruit.
The plum has an exceedingly wide range in California. It is thrifty and healthy on the immediate coast, in the interior and coast valleys, and well up into the foothills. This is perhaps most strikingly shown by the fact that every county in the state, except two perhaps (one being the city of San Francisco), contains plum or prune orchards, or both. When it is considered that this covers an area of nearly 160,000 square miles, extending through 9 1/2 degrees of latitude, a fair estimate of the adaptability of this fruit to varying conditions of soil and climate will be obtained. By choosing varieties ripening in succession, the California plum season may be extended from May to December. It is not surprising, then, that the acreage devoted to plums and prunes is one of the largest in the state, reaching a total of nearly 142,000 acres, an aggregate of nearly 11,000,000 trees, of which about four-fifths are prunes. Placer County leads in the acreage of plums with 5,500 acres, and Santa Clara in prunes with 58.400 acres. This great industry has developed since the discovery of gold. The early Mission plantings (1769-1823) included varieties of European plums, a few of which were able to survive after the abandonment of the Missions in 1834, by reproducing themselves by suckers. One variety found at Mission Santa Clara was grown and marketed as the "Mission prune" as late as 1870. The introduction of mproved plum varieties, however, dates back to 1851, when the first grafted fruit-trees were brought to the state by Seth Lewelling from Oregon, where he and his brother had established nurseries in 1847. Prior to this introduction, however, the miners were supplied with fruit of the native plums. The first importation of prune cions from France by the United States Patent Office in 1854 did not reach California. It was not until two years later that Pierre Pellier brought with him to San Francisco a small package of cions from the famous prune district of Agen, in France, which arrived in fairly good condition and were at once sent to Pellier's brother, Louis, who had already established a nursery and fruit-garden in the Santa Clara Valley, upon a portion of the site of the present city of San Jose . From these cuttings, a number of trees were produced which succeeded admirably, and eventually were distributed through different sections of the state, but principally in the Santa Clara Valley, which to this day remains the center of the California prune industry. In 1863, the first California- grown and -cured prunes were exhibited at the State Fair in Sacramento; but it was not until 1870 that planting on a commercial scale was begun. Through the seventies, and especially after 1878, numerous orchards were set out, until in 1881 some of the larger growers were producing between five and six tons of cured fruit. Since 1881 the growth of the prune industry has been marvelous, until now there are growers whose annual products reach hundreds of tons.
Considerable difficulty was at first encountered in the selection of the proper grafting stocks. The native species, first used to some extent, were soon found to be unsatisfactory, on account of suckering, and dwarfing effect. Peach, apricot, and almond roots were used, the peach and almond proving best. The introduction of the Myrobalan or French cherry-plum (Prunus cerasifera) and its adoption as a grafting stock for plums and prunes have greatly simplified matters. It does not sucker, and experience has shown that in California it succeeds in low moist lands, in comparatively dry soils, if not too loose, and in stiff upland clay soils. It thus has become the all-round plum stock in California. On deep mellow loam soils, specially adapted to the peach, that root is still preferred for plum stock; but many varieties, e.g., the Columbia, Yellow Egg, and the Washington, do not unite well with it, and cannot, therefore, be worked directly upon it. The almond is widely used in loose, warm, or rocky foothill soils, and the deep light valley loams for the French and Fellenberg prunes. The Myrobalan seedling, then, is used almost entirely, except in special cases, as an all-satisfactory grafting stock for the plum in California. Propagating the Myrobalan stock from cuttings has been practically abandoned, and seedlings are now the rule. This is all-important in California, for there the roots of all plants must necessarily go deep for their moisture and nourishment. In fact, deep-rooting is the rule beyond all common expectation; thus almond roots the thickness of one's thumb have been found at a depth of 22 feet—one of the many instances of the characteristic conditions of California agricultural practice.
Propagation is by both buds and grafts. The usual practice is to bud the young stock in July and August, and then, in January and February following, all those which have not taken can be grafted, thus securing two chances. When peach or almond is used as stock, budding alone is done, as these stocks have been found to take the graft poorly. The trees are not allowed to remain in nursery longer than one year after budding, and in many cases are set out the spring following, as "dormant buds." In early days the tendency was to rather close planting, in some cases as close as 16 feet; but later plantings were made with wider distances, until from 20 to 24 feet has come to be the rule. The laying out of orchards has caused much discussion, some asserting that the quincunx, hexagonal, and triangular systems secure better use of the land and allow better access to plow and cultivator than do the plantings in squares. The square system, however, has come to be most generally used. The style of tree is the low- headed vase-form. The rule is to cut back the young trees at planting to 18 to 24 inches. Until the top is formed the stems are protected, by whitewashing or wrapping with burlap, from the hot afternoon sun. The first year from three to five branches are allowed to grow from the stem, and these used to form the main limbs of the tree. From this time the pruning is done according to the usual methods for the vase-form tree. Many plums, owing to the brittleness of the wood, are yearly pruned rather short but the French prune is able to carry fruit on much longer branches. After the third or fourth season, the growth of wood is much less and usually the pruning operations are confined to keeping the tree in shape, removal of dead or damaged branches, and shortening-in the current season's growth to keep the young twigs in a vigorous growing condition and to prevent overbearing. The long slender branches are not cut back. The long arching "canes" are allowed to remain until they have produced a crop (which they do in the second season with the greatest profusion), the ends resting upon the ground as the fruit gains weight. When these droop too low, they are cut back to the crown, when others will be produced to take their places.
Thorough and persistent tillage is one of the first principles of the California orchardist, for with him the absence of summer rains makes the conservation of the winter rainfall an absolute necessity. Even in the summer-irrigated districts the soil is tilled and kept loose as soon as it is in proper condition, and no weeds allowed to rob the trees. Formerly all the prune and plum crop was produced without summer irrigation. Winter irrigation was often practised and the water conserved in the soil by the usual methods of tillage. But regular bearing of fruit of good size requires adequate moisture. The installation of pumping plants and irrigation systems, therefore, has received a great impetus, and the use of summer irrigation when required is an established practice.
In some of the older orchards, the need of fertilizing is beginning to be felt. In a great many, the main deficiency has been found to be vegetable matter, and, consequently, nitrogen. The extremely fine tilth which has been maintained has resulted in the destruction of all natural green growth and the "burning out" of the humus, and has necessitated the call for a green- manure crop. This problem is rendered more difficult in California by the fact that any such crop must be produced during the winter months and be ready to plow-in with the beginning of tillage in March; for no summer-growing crop can be allowed in the orchard, unless the land is regularly irrigated and then alfalfa may be grown. On non-irrigated orchards, winter- growth of hardy legumes, as vetches, is undertaken.
As mentioned above, the plum has few serious enemies in California, and none which cannot be held in check by spraying and other treatment. Upon the leaves the plum aphis and the canker-worm have given some trouble. The "peach-moth" has been found at work on the prune trees, but not to any serious extent. The trees are subject to the attacks of the black scale (Saissetia oleae), apricot scale (Lecanium corni), frosted scale (L. pruinosum) and pernicious scale (Aspidiotus perniciosus) being the most frequent; all of which, however, the California fruit-grower has learned to keep in check. The crown root-knot has also caused considerable trouble. Relief has been secured by cutting off the knots and painting the wounds with bordeaux mixture. In one district the peach root-borer has established itself and requires regular treatment. Thrips have also done some injury to blossoms and young fruit. In California some fruit is usually borne the third year; in the fourth a fairly profitable crop is expected; the fifth, from 50 to 60 pounds to a tree should be produced, which ought to double in the sixth, and after that from 150 to 300 pounds is the rule. These figures apply mostly to the prunes. From 200 to 300 pounds are considered the average at full bearing in the Santa Clara Valley. In some instances 600 and even 800 pounds have been produced, and a six-year-old tree at Visalia (San Joaquín Valley) is credited with 1,102 pounds of fruit in one season.
It would be impossible to enumerate a full list of the varieties actually in successful cultivation within the state. Such a list would probably include every noteworthy variety of domestica plum. Many, however, despite excellence of quality and flavor, are suited only for home-growing, or at most for local markets, on account of poor shipping qualities. For this reason the number of varieties planted on a large scale is being constantly reduced. At the head of the list stands the Prune d'Agen,
the originally introduced French prune, which has proved itself adapted to more varying conditions than any other variety, and is therefore perhaps the most generally planted variety of fruit in the state. It is, of course, used chiefly for curing. In the same category belong the Robe de Sergeant, Imperial Epineuse, Silver, and Sugar—all drying varieties. The Robe de Sergeant (supposed to be a synonym of the Prune d'Agen in France) in California is grown as a distinct variety. The fruit is larger, usually more highly flavored, and has commanded higher prices in the San Francisco market. The tree, however, has not proved so widely adaptable, and is in disfavor on account of defective bearing. The Silver prune (an Oregon seedling of Coe Golden Drop) is also a defective bearer in some districts, and is used mostly in the preparation of "bleached prunes," for which it has proved very profitable in some instances. It is sometimes marketed in the fresh state also. The Imperial Epineuse, a recently introduced French variety was largely planted but though large, it has proved rather irregular in bearing, difficult to cure and very subject to thrip injury. Luther Burbank's Sugar prune bases its claims upon superior earliness, sweetness and flavor, together with fair medium size. It dries easily but is of coarse texture. The German prune, Italian (Fellenberg), Golden prune, Hungarian (Pond Seedling) and Tragedy are varieties sometimes used for curing, but are frequently shipped green as "plums." Of these the German is perhaps the most extensively used. The Italian succeeds well along the coast in places liable to fogs or sea winds, where the French is not at its best. It is valuable as a late variety, and is said to dry excellently, as does also the Golden, an Oregon seedling. The fruit of the Hungarian (Pond) is very handsome and showy, and is rated, on its style, a good seller as fresh fruit in both the local and distant markets, but is not suitable for drying. The Tragedy and the Clyman (California seedlings), Giant (Burbank's), Royal Hative, Simon, and Peach, are popular for early market—especially for eastern shipment. For canning, Coe Golden Drop and the Imperial Gage are the most popular. The Jefferson, Washington, and Yellow Egg are all highly regarded, and planted more or less widely, as they suit the different climatic regions. Many of the Japanese plums are grown. Red June, Satsuma, Burbank, Wickson, Climax, Santa Rosa, and Formosa (all Burbank varieties) are prominent for eastern shipment, local market and domestic use. See Wickson's "California Fruits and How to Grow Them," the Reports of the California State Board of Horticulture, and the Reports and Bulletins of the California Experiment Station.
ARNOLD V. STUBENRAUCH.
E. J. WlCKSON.
Plum, Cherry: Prunut cerasifera. P., Cocoa: Chryso- balanue Icaco. P., Date: Diospyros. P., Governor's: Flacourtia Ramontchi. P., Japan: Properly prunus salicina; improperly applied to the loquat, Eriobotrya japonica. P., Marmalade: Lucuma mammusa.