Chapter II: Plum Culture (1)

Ten states produced over 82 per ct. of the plum crop of the United States in 1899. The census of 1900 shows that in the preceding year the total crop in the country was 8,764,032 bushels of which California, Oregon, New York, Washington, Michigan, Iowa, Texas, Arkansas, Ohio and Kansas, named in order of yield, produced 7,429,248 bushels. All other states yielded 1,334,784 bushels. Of these ten states, three, California, Oregon and Washington, holding first, second and fourth places in production, use by far the greater parts of their crops for prunes. Four others, Iowa, Texas, Arkansas and Kansas, grow the native and Triflora varieties almost exclusively. New York with a crop of 313,668 bushels in 1899, Michigan with 213,682 bushels the same year and Ohio with 81,435 bushels, grew the main crop of Domesticas for the states in which plums are not made into prunes.

At the end of the Nineteenth Century the plum ranked third in commercial value among orchard products, being surpassed by the apple and the peach. The increase in number of trees and bushels of fruit for the whole country for the decade ending with 1899 was remarkable, being for trees 334.9 per ct. and for bushels of fruit 243.1 per ct. These great increases were due to very large planting of plums for prunes on the Pacific Coast and to the widespread distribution during these ten years of native and Triflora varieties. It is very doubtful if the percentage of increase has been nearly so great during the present decade. It is likely that the development of rapid transportation and refrigerator service between the great plum-growing region of the far West and the markets of the East has caused a decrease in trees and production in the eastern states.

Plum-growing, as with the growing of all fruits, is confined to localities geologically, climatically and commercially adapted to the industry. If we take New York as an example we find that plums are grown largely only in ten of the sixty-one counties, according to the census of 1900. These with the number of trees in each are as follows: Niagara 184,133, Ontario 92,917, Seneca 59,205, Monroe 57,246, Schuyler 48,336, Orleans 41,985, Yates 32,742, Albany 32,373, Erie 30,281, Wayne 30,047. Over 62 per ct. of all the trees in the State are in these counties and probably they produce more than 90 per ct. of the plums sent to market.

A canvass of the acreage of four hundred plum-growers in New York shows that the following in order named are the leading commercial varieties: Bradshaw, including Niagara, which is identical, Reine Claude including its several near variations, Italian Prune, German Prune, Lombard, Shropshire, Grand Duke, Washington and Gueii. Abundance and Burbank are as widely distributed as any of these, chiefly owing to the zeal with which nurserymen have sold these varieties, but are seldom grown exclusively in commercial plantations, and their popularity is now on the wane as is also the case with Red June which has been largely planted. Varieties of native plums are hardly grown in New York though now and then they are found in home collections and there are a few small commercial plantations of them.

The fruit of the native and Triflora plums is so inferior to that of the Domestica sorts for market and domestic purposes, that varieties of these are not likely to take the place of the Domestica plums. Producers and purchasers are now familiar with the possibilities of the natives and of the Orientals and have not been greatly attracted by them in New York. It is true, however, that the natives have been chiefly represented by Wild Goose and the Trifloras by Abundance and Burbank—scarcely the best that these groups of plums can produce. It is true, too, that the varieties have been greatly over-praised and that they now suffer from the reaction. Yet the Domesticas command the market and their reliableness in the orchard gives them a popularity in this region which other plums cannot for a long while trench upon.

This brings us to a discussion of the conditions under which plums are now grown in North America and more particularly in New York. Of these, climate, with this fruit, should be first discussed, outranking all others in importance.

CLIMATE

Climatic conditions determine the culture of the plum not only for a region but for a locality; not only as to whether it is possible to grow plums at all but as to whether this fruit can be grown with reasonable prospects of commercial success in competition with other localities. The constituents of climate which are important in plum-growing are temperature, rainfall and air currents, the last two being largely dependent upon the first. The relationship existing between plums and these factors of climate are fairly well known for they have received attention from the very beginning of plum culture.

There are four phases of temperature that need to be considered in order to get a clear insight into the climatic conditions which govern production of fruit crops. These are, the daily, monthly and annual changes in temperature and the extremes in temperature. Of these the daily and annual changes are of little importance. All plants are very adaptable to daily variations in climate and are little affected by them. Annual variations are shown by statements of the annual mean temperatures but such statements are of small value to fruit-growers as they may be the result of averaging very divergent temperatures or temperatures very close together. The monthly mean, however, is a very fair criterion of climate for fruit-growing, especially when given with the amount and distribution of rainfall.

But far more important than any of the above phases are the extremes in temperature and more particularly of cold. A plant can not be grown profitably where the temperature, even occasionally, falls below the point where winter-killing results to tree or bud, or where the blossom is injured by frost. Extremes of heat are disastrous usually only when long continued. For each fruit, too, there must be a total amount of heat available to carry it from the setting of the fruit to maturity, in which respect varieties of any fruit may differ materially. Of the injurious effects and of the necessary amounts of heat, however, we know but little.

These general considerations of temperature lead us to their application to the plum and especially to a discussion of the most important of the several factors—hardiness.

Hardiness to cold, a matter of prime importance with all fruits, is especially so with the plum because of the many different species, each with its own capacity for withstanding cold. As the different species are taken from their natural habitat to other regions, there to become acclimatized, and as new forms originate by hybridization, the matter becomes more complicated and more important. Waugh[145] has investigated the hardiness of plums and we publish a table given by him showing the hardiness of representative varieties of the species most generally cultivated. We have taken the liberty of adding a few plums not given in the original table and have also made some changes in the nomenclature of the groups.

TABLE SHOWING THE HARDINESS OF REPRESENTATIVE VARIETIES OF PLUMS AT VARIOUS PLACES.

h—hardy; hh—half-hardy; t—tender.

==================+===+===+===+===+===+===+===+===+===+===+===+===+===
| | | | | | | W.| | | | | |
| | | | | | | | | | | W | | M
| | | I | | C | N | N | | | | i | | i
| | I | l | | o | e | e | V | O | | s | | n
| | n | l | K | l | b | w | e | n | | c | | n
| | d | i | a | o | r | | r | t | M | o | | e
| O | i | n | n | r | a | Y | m | a | a | n | I | s
| h | a | o | s | a | s | o | o | r | i | s | o | o
| i | n | i | a | d | k | r | n | i | n | i | w | t
| o | a | s | s | o | a | k | t | o | e | n | a | a
------------------+---+---+---+---+---+---+---+---+---+---+---+---+---
Americana Plums: | | | | | | | | | | | | |
De Soto | h | h | h | h | h | h | h | h | h | h | h | h | h
Hawkeye | h | h | h | h | h | h | h | h | h | h | h | h | h
Wolf | h | h | h | h | h | h | h | h | h | h | h | h | h
| | | | | | | | | | | | |
Domestica Plums: | | | | | | | | | | | | |
Lombard | h | h | h | h | h | h | h | h | h | h | h | h |hh
Reine Claude | h | h | h | h | h | h | h | h |hh | h |hh | h | t
Bradshaw | h | h | t |hh | h | h | h |hh |hh |hh |hh |hh | t
Arctic | h | h | h | h | h | h | h | h | h | h | h | h |hh
| | | | | | | | | | | | |
Hortulana Plums: | | | | | | | | | | | | |
Moreman | h | h | h | h | h | h | h | h | h | ? | h |hh | t
Golden Beauty | ? | h | h | h | h | ? | h |h? | ? | ? |hh | h | t
Wayland | h | h | h | h | h | ? | h | h | ? | ? |hh |hh | t
| | | | | | | | | | | | |
Insititia Plums: | | | | | | | | | | | | |
Damsons | h | h | h | h | h | h | h | h | h | h | h | h |hh
| | | | | | | | | | | | |
Munsoniana Plums: | | | | | | | | | | | | |
Pottawattamie | h | h | h | h | h | h | h | h |hh | t | h | h | h
Newman | h | h | h | h | ? | ? | h | ? | t | t |hh | t | t
Robinson | h | h | h | h | ? | ? | h | ? | t | t | t |hh | t
| | | | | | | | | | | | |
Nigra Plums | h | h | h | h | h | h | h | h | h | h | h | h | h
| | | | | | | | | | | | |
The Simon Plum | h | h | h | h |hh |hh | h |hh |hh | t | t | t | t
| | | | | | | | | | | | |
Triflora Plums: | | | | | | | | | | | | |
Abundance | h | h | h | h |hh | h | h | h | h |hh |hh |hh | t
Burbank | h | h | h | h | h | h | h | h | h |hh |hh |hh | t
Satsuma |hh | h | h |hh | t | h |hh |hh |hh | t | t |hh | t
Kelsey | t | ? | t |hh | t | t | t | t | t | t | t | t | t
==================+===+===+===+===+===+===+===+===+===+===+===+===+===

A few general statements in addition to the above table will help to make plain the comparative hardiness of the different groups of cultivated plums. The Nigras may be rated as the hardiest of the plums to be considered though the Americanas are but slightly less hardy. The plums of these species are the hardiest of our tree-fruits and are able to resist nearly as much cold as any other cultivated plant. The Insititias, as represented by the Damsons, at least, come next hardiest after the above species, with varieties of Domestica, as Arctic, Lombard and Voronesh, nearly as hardy. So far as resistance to cold is concerned the Domestica plums as a class are less hardy than the apple, ranking in this respect with the pear. Of the Domesticas the Reine Claude plums are as tender to cold as any though some consider Bradshaw as more tender. Between these last sorts and the hardiest varieties there is a great range in capacity to endure cold, as would be expected with so large a number of varieties originating in widely separated climates. The Triflora plums vary more in hardiness than any other of the cultivated species. Speaking very generally they are less hardy than the Domesticas, the hardiest sorts, Burbank and Abundance, being somewhat hardier than the peach, while the tenderest varieties, of which Kelsey is probably most tender, are distinctly less hardy than the peach. Of the remaining plums, the Hortulana, Munsoniana and Watsoni groups, there are great diversities in opinion as to hardiness. Probably all of the varieties in these last groups are as hardy as the peach with a few sorts in each more hardy than the peach. It is to be expected from the more northern range of the wild prototypes that the Hortulana and Watsoni plums are somewhat hardier than _Prunus munsoniana_.

The rainfall is of comparatively small concern to plum-growers in America, since, with now and then an exception, in eastern America it is sufficient under proper cultivation, and on the Pacific Coast the crop is largely grown under irrigation. Summarized statements of annual rainfall are of little or no importance since almost all depends upon the distribution of the amount throughout the year and upon the manner in which it falls. Monthly and seasonal “means” of precipitation, as in the case of temperature, may be of considerable importance in determining the desirability of a locality for plums.

Air currents are of local or regional occurrence and though not often the determinant of profitable culture of plums have sometimes been important factors in choosing a location to grow this fruit. The occurrence, direction, moisture condition and temperature are the attributes of air currents usually considered. The failure of many plums to grow in the prairie region of the Mississippi Valley and the Great Plains is no doubt due in some measure to winter winds. The problem of varietal adaptation is more or less complicated in any region by the nature of the air currents.

An extremity of any of the constituents of what we call “weather” endangers the plum crop at blossoming time. In New York stresses of weather are probably the predominating causes of the non-setting of fruit on plum trees which bear an abundance of blossoms. This is well shown in a study of the relations of weather to the setting of fruit made by the New York Agricultural Experiment Station in which it is held that several phases of weather at blossoming time cause the loss of plum crops.[146] Thus late frosts, wet weather, low temperature, strong winds and wide daily ranges in temperature were factors in the loss of fruit crops in all of the failures during a period of twenty-five years. Quite as significant was the fact that in all of the years during this period when there was sunshine and warm, dry weather during blossoming time there were good crops of fruit.

Locations for growing the different varieties of plums are selected with reference to general and local climate. As regards general climate, latitude, altitude and proximity to large bodies of water are the chief determining characters; as regards local climate, the lay of the land has most to do as a determinant. Again, varieties are selected with reference to time of blooming, that they may escape in some degree injurious climatal agencies. Lastly, varieties are selected having greater capacity, from one cause or another, to withstand injurious weather. With all varieties it is found that cultural treatment to induce strong vitality helps a tree to withstand stresses of harmful weather at blossoming time.

The above considerations show that the blossoming dates of plums should be known for the proper culture of this fruit. In the following table averages of the blooming dates of varieties of plums for the eight years just past, 1902 to 1909, inclusive, are given.

In making use of these dates, consideration must be given to the environment of the orchards at Geneva. The latitude of the Smith Astronomical Observatory, a quarter of a mile from the Station orchards is 42° 52′ 46.2″; the altitude of the orchards is from five hundred to five hundred and twenty-five feet above the sea level; the soil is a stiff and rather cold clay; the orchards lie about a mile west of Seneca Lake, a body of water forty miles in length and from one to three and one-half miles in width and more than six hundred feet deep. The lake has frozen over but a few times since the region was settled, over a hundred years ago, and has a very beneficial influence on the adjacent country in lessening the cold of winter and the heat of summer, and in preventing early blooming.

The dates are those of full bloom. They were taken from trees grown under normal conditions as to pruning, distance apart, and as to all other factors which might influence the blooming period.

An inspection of the table shows that there is a variation of several days between the time of full bloom of the different varieties of the same species. These differences can be taken advantage of in selecting sorts to avoid injury from frost. The same table shows the ripening season of the plums growing on the Station grounds. Now and then the late and very late plums given in the table may be caught by fall frosts in the colder parts of New York or in regions having a similar climate.

TABLE SHOWING BLOOMING DATES AND SEASON OF RIPENING.

The “blooming date” is that of full bloom.

Under season of ripening “very early” is from July 15 to August 10; “early,” August 10 to August 20; “mid-season,” August 20 to September 10; “late,” September 10 to September 20; “very late,” September 20 to October 1.

================+=========================+============================
| Blooming date | Season of ripening
----------------+-------------------------+-----+-----+------+----+----
| May | | | | |
|-------------------------|Very |Early| Mid- |Late|Very
|1 1 1 1 1 1 1 1 2 2 2 2 2|early| |season| |late
|2 3 4 5 6 7 8 9 0 1 2 3 4| | | | |
----------------+-------------------------+-----+-----+------+----+----
| | | | | |
_P. americana_: | | | | | |
De Soto | * | | | * | |
Hawkeye | * | | | * | |
New Ulm | * | | | * | |
Ocheeda | * | | | * | |
Oren | * | | | * | |
Rollingstone | * | | | | |
Stoddard | * | | | * | |
Surprise | * | | | * | |
Wolf | * | | | * | |
Wood | * | | | * | |
Wyant | * | | | * | |
| | | | | |
_P. cerasifera_:| | | | | |
De Caradeuc |* | * | | | |
Golden Cherry |* | * | | | |
| | | | | |
_P. domestica_: | | | | | |
Agen | * | | | | * |
Altham | * | | | * | |
American | * | | | * | |
Arch Duke | * | | | * | |
Autumn Compote| * | | | | * |
Arctic | * | | | | |
Bavay | * | | | | | *
Béjonnièrs | * | | | | * |
Belgian Purple| * | | | * | |
Belle | * | | | | * |
Bradshaw | * | | | * | |
Bryanston |* | | | * | |
Chambourcy | * | | | | | *
Champion | * | | * | | |
Cling Stem | * | | | | * |
Clyman | * | * | | | |
Czar | * | * | | | |
Dawson | * | * | | | |
Diamond | * | | | * | |
Doretts | * | | | * | |
Duane | * | | | * | |
Early Rivers | * | | * | | |
Early Orleans | | | | * | |
Early Royal | * | | | * | |
Early Tours | * | * | | | |
Empire | * | | | * | |
Englebert | * | | | * | |
Esjum Erik | * | | | * | |
Field | * | | | * | |
Freeman | * | | | * | |
Furst | * | | | | * |
German Prune | * | | | | * |
Giant | * | | | * | |
G. No. 4 | * | | | * | |
Golden Drop | * | | | * | |
Golden Gage | * | | | * | |
Goliath | * | | | * | |
Grand Duke | * | | | * | |
Gueii | * | | | * | |
Guthrie Late | * | | | * | |
Hand | * | | | * | |
Harriet | * | | | * | |
Hector | * | | | * | |
Hudson | * | | | * | |
Hungarian | * | | | * | |
Ickworth | * | | | * | |
Imperial | | | | | |
Epineuse | * | | | * | |
Imperial Gage | * | | | * | |
Italian Prune | * | | | | * |
Jefferson | * | | | * | |
Kirke | * | | | * | |
Lafayette | * | | | | * |
Large English | * | | | | * |
Late Orleans | * | | | * | |
Late | | | | | |
Muscatelle | * | | | | * |
Lombard | * | | | * | |
Lucombe | * | | | * | |
Middleburg | * | | | | | *
Miller No. 1 | * | | | * | |
Miller Superb | * | | | * | |
Missouri | | | | | |
Green Gage | * | | | * | |
Morocco | * | | | | * |
Mottled Prune | * | | | * | |
Newark | * | | * | | |
Nicholas | * | * | | | |
Ottoman | | | | | |
Seedling | * | | * | | |
Oullins | * | | * | | |
Pacific | * | | | * | |
Palatine | * | | | * | |
Paul Early | * | | * | | |
Pearl | * | | | * | |
Peters | * | | | * | |
Pond | * | | | | * |
Purple Gage | * | | | * | |
Quackenboss | * | | | * | |
Red Date | * | | | * | |
Sannois | * | | | | |
Saunders | * | | * | | |
Sheldrake | * | | | * | |
Shipper | * | | | | * |
Smith Orleans | * | | | * | |
Spaulding | * | | | * | |
Stanton | * | | | | * |
St. Catherine | * | | | | * |
Sugar | * | | | * | |
Tennant | * | | | * | |
Tobias Gage | * | | | * | |
Tragedy | * | | * | | |
Transparent | * | | | | * |
Ungarish | * | | | | * |
Union | * | | | * | |
Uryany | * | | | | * |
Victoria | * | | | | |
Voronesh |* | | | * | |
Warner | * | | | | | *
Washington | * | | | * | |
Wyzerka | * | | | * | |
Yellow Egg | * | | | | * |
Yellow Gage | * | | | * | |
York State | | | | | |
Prune | * | | | | * |
| | | | | |
_P. hortulana_: | | | | | |
Golden Beauty | * | | | | | *
Wayland | *| | | | | *
World Beater | * | | | | | *
| | | | | |
HYBRIDS: | | | | | |
America | * | | * | | |
Ames | * | | | * | |
Apple | * | | * | | |
Bartlett | * | * | | | |
Climax | * | * | | | |
Downing | * | | | * | |
Golden | * | | | * | |
Hammer | * | | | * | |
Japex | * | * | | | |
Juicy | * | | | * | |
Marianna | * | | | * | |
Milton | * | * | | | |
Shiro |* | * | | | |
Sophie | * | | | | |
Wickson | * | | | * | |
| | | | | |
_P. insititia:_ | | | | | |
Black Bullace | * | | | | | *
Crittenden | * | | | | * |
Freestone | * | | | * | |
French | * | | | | * |
Frogmore | * | | | | * |
King of | | | | | |
Damsons | * | | | | * |
Late Mirabelle| * | | | | |
Mirabelle | * | | | * | |
Reine des | | | | | |
Mirabelles | * | | | | * |
Shropshire | * | | | | * |
Sweet Damson | * | | | * | |
White Bullace | * | | | | |
| | | | | |
_P. hortulana | | | | | |
mineri:_ | | | | | |
Forest Garden | * | | | | * |
Maquoketa | * | | | | * |
| | | | | |
_P. munsoniana:_| | | | | |
Arkansas | * | | * | | |
Newman | * | | | * | |
Poole Pride | *| | * | | |
Pottawattamie | * | | * | | |
Robinson | * | | | | |
Wild Goose | * | * | | | |
| | | | | |
_P. nigra:_ | | | | | |
Cheney | * | | | * | |
| | | | | |
_P. triflora:_ | | | | | |
Abundance | * | | * | | |
Burbank | * | | | * | |
Chabot | * | | | | * |
Engre | * | | * | | |
Earliest | | | | | |
of All |* | | * | | |
Georgeson |* | | * | | |
Hale |* | | * | | |
Long Fruit | * | * | | | |
Maru | * | | * | | |
Ogon | * | | | | |
----------------+-------------------------+-----+-----+------+----+----

THE POLLINATION OF PLUMS.

One of the discouragements in plum-growing is the uncertainty which attends the setting of the fruit in some varieties even though the trees bear an abundance of blossoms. Blooming, the prelude of fruiting, had little significance to the fruit-grower until the discovery was made that many varieties of several fruits were unable to fertilize themselves and that failures of fruit crops were often due to the planting of infertile varieties. Investigations as to the self-sterility of pears, plums and grapes have shown blossoming-time to be one of the most important life periods of these fruits. The knowledge obtained by workers in this field has to some degree modified the planting of all orchard-fruits and of none more than of the plums. Indeed, it is held by many that it is hardly safe to plant any excepting the Domestica and Insititia plums without provision for cross-pollination.

A variety is in need of cross-pollination when the pollen from its own blossoms does not fecundate the ovules of the variety. There is a delicate and complicated procession during the process of fruit formation and the life of the fruit may be jeopardized by any one of a number of external or internal influences. These deleterious influences are most often unfavorable weather or defects in the reproductive organs of the plants themselves. Of the latter, in the plum there are several rather common ones which cause self-sterility, as impotency of pollen, insufficiency of pollen, defective pistils and difference in the time between the maturity of the pollen and the receptiveness of the stigmas.

It is held that the main cause of the infertility in plums is impotency of pollen on the pistils of the same variety. The pollen may be produced in abundance, be perfect as regards appearance, and potent on the pistils of other varieties but wholly fail to fecundate the ovaries of the variety from which it came. The most marked examples of such impotency are to be found in the native plums though the Triflora sorts are generally accredited with being largely self-sterile and the Domesticas somewhat so. The proof offered to show the impotency of plums is for most part the records of fruit setting under covered blossoms. In this method of testing the impotency of pollen there are several sources of error and the figures given by experimenters probably greatly exaggerate the infertility of plums, but since the experience of plum-growers generally affirms the results in some measure it is well to hold that the native plums at least should be so planted as to secure cross-pollination. It is doubtful if the Domestica and Triflora plums are self-sterile and yet the question is an open one as regards some varieties of these species.

There is great difference in the quantity of pollen produced by the several groups of plums but it is very doubtful if insufficiency of pollen is a factor of any considerable importance in the self-sterility of this fruit. Yet the matter is worth attention because of its bearing upon the selection of pollinizers. Of the several botanic groups, speaking somewhat generally, the Americanas and Nigras bear most pollen; the Munsoniana plums are abundant pollen bearers; the Trifloras seldom show a shortage but bear rather less than the others named; the Domesticas produce pollen abundantly; while the hybrid groups are the most capricious of all the plums in this respect, some varieties bearing much and others but little pollen. Probably the amount of pollen which the flowers of any tree produce is somewhat modified by the climate in which the tree is growing, by the weather and by the vigor of the tree.

Waugh[147] and Goff[148] have shown that self-sterile plums often have abnormal pistils or pistils too weak for the development of fruits. Not infrequently flowers of the plum are without pistils, as occasionally, but less rarely, occurs with the stamens and petals. These abnormalities cannot be very general causes of self-sterility in plums, however, as varieties, or even trees, cannot often be found which are not fruitful if other varieties are growing near them. It is very doubtful if even so much as fifty per ct. of abnormal flowers, seriously jeopardizes a plum crop, as the trees bear, if they blossom at all, several times as many flowers as they can mature plums. But a high percentage of abnormal flowers nearly always indicates a general weakness in fruit-setting.

Another cause often assigned for the failure of plums to set fruit is the difference in time of maturity of stamens and pistils. It is claimed that when these organs do not mature simultaneously the plums do not set unless pollen is supplied from some other source. The task of taking notes at blossoming time on more than three hundred varieties of plums on the grounds of this Station has given abundant opportunity to observe the comparative degrees of maturity of pistils and stamens in varieties of this fruit. In general the pistils mature first, often three or four days before the stamens. Rarely the pollen is disgorged before the stigmas are receptive. But stigmas remain receptive, weather conditions being favorable, for several days and the pollen from all anthers is not shed at once and is produced with such seeming prodigality as to almost insure the retaining of a sufficient amount to pollinate late-maturing stigmas. In view of these considerations, premature or retarded ripening of either pistils or stamens does not seem of great significance in the setting of fruit.

From the statements just made it may be seen that the main cause of the failures to set fruit when trees bloom freely must be ascribed to the failure of pollen to fertilize the pistils of the flowers of the same variety. The solution of the problem of self-sterility in the main, then, is to so plant that varieties will be mutually cross-fertilized. In the selection of varieties for such cross-pollination two factors must be considered, simultaneity of blossoming and sexual affinity.

It is evident, if cross-fertilization is to play an important part in fruit-growing, in planting to secure it kinds must be chosen which come into blossom at the same time as those they are expected to fertilize. The table on pages 106 to 109 shows the sorts that bloom together or nearly enough so to make cross-pollination possible. It will be found upon examining the table that, under normal conditions and during the average season, varieties of any one species overlap sufficiently for the above purpose unless it be the very early and very late varieties. Variations due to locality and to season must be expected but within the bounds of New York these will be slight. If the table is used for other regions than New York it must be borne in mind that the farther south, the longer the blossoming season; the farther north, the shorter the season. Properly interpreted the table of dates should be a useful guide as to the simultaneity of blooming.

Varieties of plums seem to have sexual affinities. That is, some varieties will fertilize each other very well and some will not, even though they belong to the same species. There seems to be little definite knowledge as to the sexual affinities of plums and it is not, therefore, possible to lay down exact rules for the selection of pollinizers for individual varieties. In the current discussions of cross-pollination it is probable that the importance of “affinities” is over-rated, and yet the subject is worthy of consideration. Waugh and Kerr have given this subject considerable attention for native and Japanese plums and have recommended a list of pollinizers for the several species.[149] The Domesticas and Insititias, the above writers hold, are best cross-pollinated by varieties from the same species if cross-pollination is essential.

The subject cannot be closed without the expression of the opinion that the lack of cross-pollination as a cause of the uncertainties in the setting of fruit has been over estimated in the planting of plum orchards. This expression of doubt is made because there are serious disadvantages in the planting of mixed orchards of any fruit and the question as to whether these do not outweigh the advantages must ever be considered.

LOCATIONS AND SOILS FOR PLUMS.

The plum is comparatively easy to suit in the matter of location of orchards, as is shown by the exceedingly wide range of this fruit in New York. Plums are grown with eminent success on the elevated and sloping lands adjoining the Great Lakes, the Central Lakes of western New York and on both banks of the Hudson. Unquestionably there are many other localities than those named about the waterways of the State and also upon the elevated lands in the western interior formed by morainic hills, and upon the slopes of the mountains in eastern New York. Upon any land in the State suited to general farm crops, where the severity of winter is tempered by the lay of the land or proximity to water, and where late spring frosts are infrequent, plums may be grown. The early blooming plums, the Trifloras in particular, require more or less consideration as to the slope of land, a northern exposure to retard blooming-time being best. With other species the direction of the slope makes little difference, though a slope for air and water drainage is always better than a dead level.

The plum is now thriving in New York, and in the country at large, in a great diversity of soils. The chief requisite for the genus in general seems to be good drainage. Given this condition, some sort of plums can be grown on almost any soil found in America not wholly prohibitive of plant growth. Plums can be found which will stand rather more water than any other of the tree-fruits, and since plums can be grafted on several stocks, each having its own adaptation to soils, the adaptability of the genus is still further increased. Yet the several species have somewhat decided soil preferences.

The Domesticas and Insititias, the plums now almost exclusively grown in New York, grow most satisfactorily, all things considered, on rich clay loams. The plum orchards in this State on such soils contain the largest and most productive trees and produce the choicest fruit from the standpoints of size, appearance and quality. Yet there are exceptions in which exceedingly fine Domestica plums are grown on light loams. The Station collection of about two hundred varieties of European plums is on stiff clay, but well drained, and the results are uniformly good. The Americanas and Nigras grow very well on much the same soils as the European sorts, speaking from the experience on the grounds of this Station, for varieties of these species are not generally grown in New York. Beyond question the Triflora plums, next most widely grown in New York after the Domesticas, are giving the best results on light soils—those most favorable for the peach. The ideal soil for this species is a sandy or gravelly loam but they are growing well on soils having either more sand or more clay than the ideal types. The Hortulana and Munsoniana plums incline to the comparatively light types of soils named as being best for the Trifloras rather than to the heavier lands on which the European plums are most commonly grown.

Plum-growers are well aware of the necessity of good drainage for this fruit but few seem to realize the importance of warmth in a plum soil. The plum, in common with all stone-fruits, grows best, as a rule, on soils having the power to absorb and retain heat, or if the soil have not these properties the location and the cultivation should be such as to provide as far as possible for “bottom heat.”

STOCKS AND PROPAGATION.

A discussion of stocks naturally follows one of soils, for the two are intimately related. The plum can be successfully grown on various stocks and for this reason the practices of nurserymen are diverse, depending upon the cost of the stocks, the ease with which they may be budded or grafted and the adaptability of the tree to the stocks. Unfortunately there is little experimental data to show which of the several stocks is best for the different plums and since growers seldom know what stocks their plums are growing upon they can give almost no information as to the desirability of propagating on this stock or that. Nurserymen know the stocks best adapted to their purpose and from them we have sought information.

A letter of inquiry sent to representative nurserymen in all parts of the United States as to the relative merits of the several stocks for the different species of plums shows that plum propagators in different regions use somewhat different stocks. In New England and the North Atlantic States, the Myrobalan seems to be almost the universal choice, the exception being a few propagators who claim that the Japanese sorts should be worked on the peach, especially for sandy soils, and a few others who are using Americana stocks for the American species.

In the Atlantic states south of Pennsylvania and in the Gulf states to the Mississippi the preferences are very diverse, with the majority of the nurserymen in this region favoring the peach, Myrobalan following as a close second choice. For light soils it would seem that the peach is always to be preferred for this great region. The opinions expressed by the veteran plum-grower, J. W. Kerr of Denton, Maryland, on this subject are worth printing in full. He says:

“In this locality for all varieties of the Domesticas that
unite thoroughly with it, the peach is preferable as a stock.
There are, however, a good many varieties of Domesticas that
refuse to unite firmly with the peach. For these the Marianna
or the Myrobalan gives best results. For all of the Japanese
plums the peach has proved most satisfactory, when the trees
are propagated by root-grafting on the whole-root plan. Nearly
forty years of experimenting and testing stocks of various
kinds gives me a decided preference for the peach as a stock
for native plums; results doubtless would be different in
colder climates and soils than this, but long and critical
experience has conclusively demonstrated the superiority of
this stock when used as indicated for the Japanese.”

In the interior region between the Atlantic and Gulf States and the Mississippi, the Myrobalan is used almost exclusively for the European plums and most largely for the other species. Several nurserymen from this region, however, state that the St. Julien is better than the Myrobalan for the Domesticas and Insititias but object to them because the stocks cannot be obtained as cheaply. The peach is generally recommended for the Triflora sorts and the statement is several times repeated that the Americanas would be preferred for the native species if stocks of this species could be obtained readily.

In the northern states of the Mississippi Valley, all nurserymen agree that plums must be worked on Americana stocks. In this region the hardy natives only are grown.

South of the northern tier in the states of the plains the Myrobalan is used almost exclusively for the European species, most largely for the Trifloras, with the peach second for this species, and Americana stocks for the native species. Stark Brothers of Louisiana, Missouri, large growers of nursery stock in this region, express the opinion that “the right stock for native plums is yet to be found.” In Oklahoma, Texas and New Mexico the Marianna is mentioned by several nurserymen as desirable, and is, from these statements, rather more commonly used for stocks in these states at present than in any other region.

On the Pacific Coast propagators use Myrobalan and peach in about equal quantities—the first named for heavy soils and the last for the lighter soils. The native plums are not grown in this region. The almond is mentioned as being desirable in California under some conditions. Some plum-growers in the states of the Pacific propagate their own trees from suckers.

The information given by nurserymen shows that by far the greatest number of plums in the country are grown on Myrobalan stocks. In New York this stock is used almost exclusively. In Europe the writer found that the nurserymen hold that this is a dwarfing stock, and that the trees on it are shorter-lived than on some other stocks. In the nurseries in New York, plums in general, but more especially the Europeans, are larger and finer trees at two years, the selling age, grown on Myrobalan roots than trees grown on other stocks. Nurserymen lodge but two complaints against it; these are that in the South it suckers badly and in the cold states of the Great Plains the roots are killed by the winters. Its advantages from the tree-growers’ standpoint are: Cheapness of the stock, which is usually imported from France, large handsome trees in the nursery, ease of budding and a good union with nearly all varieties. Some growers complain that certain varieties overgrow this stock making in the end a badly mal-formed trunk. The Myrobalan plums are very variable, a fact which finds record in nearly all the characters of tree and fruit and this is somewhat against it as a stock. It is for this reason that there are so many “true” and “false” Myrobalans among nurserymen. Many importers hold that this stock is grown in France from cuttings. Such it seems was the old practice but now, if information from France is correct, most of these stocks are grown from seed. Hansen reports that in South Dakota this stock is worthless because it winter-kills. He says[150] “in experiments at this Station a very small per cent. of Myrobalan stocks survived the first winter and these died the ensuing summer.” It is likely that this stock would suffer in the coldest parts of New York.

In this region the St. Julien is probably the next most common stock in plum orchards though trees on it are for most part old, as its use is on the decrease. There is a wide-spread opinion among plum-growers that this is a much better stock for Domestica and Insititia plums than any other. On St. Julien stocks varieties of these species, it is claimed, with much to substantiate the claim, produce trees that are longer-lived, thriftier, hardier, deeper feeders, sprout less and are less susceptible to changes in soils. The chief objections to this stock are: It is more expensive, sometimes scarcely obtainable in France; difficult to bud; the young trees do not make as good growth as on the Myrobalan stocks; and the yearlings are much more susceptible to fungi while in the nursery row, though the latter troubles can be remedied wholly or in part by spraying. Hansen, in the reference given above, says that “the St. Julien and European Sloe (_Prunus spinosa_) both winter-killed” in South Dakota when used as stocks. The St. Julien stock is propagated from layers when properly grown in France[151] but much undesirable stock is now raised from seed. There are fruiting trees of this stock about the nurseries in the neighborhood of this Station which show it to be an Insititia of the Damson type, a type likely to come fairly true to seed yet not sufficiently so as to make seed-grown trees desirable.

The Horse plum was formerly used as a stock by nurserymen a great deal but is now wholly superseded. Indeed, it is so nearly lost to the trade as to make it almost impossible to really know what the plum of this name is. Some describe it as a small-fruited Domestica, others as an Insititia similar to the St. Julien, but the majority of the trees shown by old nurserymen in the nursery region of New York, about the only place in which the stock was used, show it to be a Cerasifera but not Myrobalan. Some of the named varieties of Cerasifera probably sprung from sprouts of this stock. It seems to have had no qualities which would make it worth while to attempt to re-establish the stock.

The testimony of a large number of nurserymen is in favor of the peach as a stock for plums. Budded on the peach, plums of many varieties are grown very successfully on the warm sandy and gravelly soils so well suited to the peach. This stock enables the tree to make a quick growth and come into bearing early, and the roots do not produce sprouts. The budding with the peach is easily done, the young trees make a vigorous growth in the nursery and plums on peach roots can probably be grown at a less cost than on any other stock. Triflora plums in particular make excellent trees worked upon peach stock, the roots are as hardy as the tops and the union is sufficiently congenial to make the resulting tree long-lived. For the Domestica and Insititia plums the peach stock is not so valuable, for with some varieties a good union is not secured and the roots are less hardy than the tops. Among the varieties which nurserymen say will not unite with the peach are: Lombard, Damsons, Yellow Egg and Washington. Peach borers are sometimes troublesome when plums are budded on peach stocks.

Mr. Kerr, in his statement regarding stocks, on page 115, says that it is his practice to whip-graft the plum on “whole-root” peach roots obtaining eventually the plum on its own roots. This method is certainly well adapted to Mr. Kerr’s conditions but whether it would do in heavier soils and a colder climate is doubtful. One would suspect that some varieties of Domesticas and Insititias at least would sprout badly.

In the South, more particularly Texas and the Southwest, Marianna stocks find favor, though their use seems to be on the decrease. The advantages of this stock are such as appeal to the nurserymen rather than to the plum-grower. These are that the Marianna readily strikes root from cuttings and the growth in the nursery is all that can be desired. Cuttings strike more easily in the South than in the North, hence its popularity in the first named region.

For the colder parts of the Great Plains and as far east as to include Wisconsin, Americana seedlings are the only stocks that will withstand the winter. In this region Americana stocks are, of course, used only for the native plums and data seem to be lacking as to whether other plums cultivated for their fruit could be grown on this stock or not. The W. & T. Smith Company of Geneva report that they are now using Americana seedlings for native plums for their eastern trade, speaking of them as follows: “We think we get a larger growth and a better root system by using the native (Americana) stocks. We also consider that the Flowering Almonds, _Prunus triloba_ and _Prunus pissardi_, make a better growth on native stocks.” From the last statement one would suspect that it would be feasible to grow other orchard plums than the native species on this stock. As yet Americana seedlings are expensive, and until they cost less their use in competition with the Myrobalan and peach stocks will be almost precluded. The chief fault of the Americana stock is that the trees sucker rather badly.