CHAPTER II_The plums of New York

PLUM CULTURE.

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

------------------+---+---+---+---+---+---+---+---+---+---+---+---+---

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

| | | | | | | | | | | | |

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

| | | | | | | | | | | | |

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

| | | | | | | | | | | | |

Damsons | h | h | h | h | h | h | h | h | h | h | h | h |hh

| | | | | | | | | | | | |

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

| | | | | | | | | | | | |

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

|2 3 4 5 6 7 8 9 0 1 2 3 4| | | | |

----------------+-------------------------+-----+-----+------+----+----

| | | | | |

De Soto | * | | | * | |

Hawkeye | * | | | * | |

New Ulm | * | | | * | |

Ocheeda | * | | | * | |

Oren | * | | | * | |

Rollingstone | * | | | | |

Stoddard | * | | | * | |

Surprise | * | | | * | |

Wolf | * | | | * | |

Wood | * | | | * | |

Wyant | * | | | * | |

| | | | | |

De Caradeuc |* | * | | | |

Golden Cherry |* | * | | | |

| | | | | |

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 | * | | | * | |

Epineuse | * | | | * | |

Imperial Gage | * | | | * | |

Italian Prune | * | | | | * |

Jefferson | * | | | * | |

Kirke | * | | | * | |

Lafayette | * | | | | * |

Large English | * | | | | * |

Late Orleans | * | | | * | |

Muscatelle | * | | | | * |

Lombard | * | | | * | |

Lucombe | * | | | * | |

Middleburg | * | | | | | *

Miller No. 1 | * | | | * | |

Miller Superb | * | | | * | |

Green Gage | * | | | * | |

Morocco | * | | | | * |

Mottled Prune | * | | | * | |

Newark | * | | * | | |

Nicholas | * | * | | | |

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 | * | | | * | |

Prune | * | | | | * |

| | | | | |

Golden Beauty | * | | | | | *

Wayland | *| | | | | *

World Beater | * | | | | | *

| | | | | |

America | * | | * | | |

Ames | * | | | * | |

Apple | * | | * | | |

Bartlett | * | * | | | |

Climax | * | * | | | |

Downing | * | | | * | |

Golden | * | | | * | |

Hammer | * | | | * | |

Japex | * | * | | | |

Juicy | * | | | * | |

Marianna | * | | | * | |

Milton | * | * | | | |

Shiro |* | * | | | |

Sophie | * | | | | |

Wickson | * | | | * | |

| | | | | |

Black Bullace | * | | | | | *

Crittenden | * | | | | * |

Freestone | * | | | * | |

French | * | | | | * |

Frogmore | * | | | | * |

Damsons | * | | | | * |

Late Mirabelle| * | | | | |

Mirabelle | * | | | * | |

Mirabelles | * | | | | * |

Shropshire | * | | | | * |

Sweet Damson | * | | | * | |

White Bullace | * | | | | |

| | | | | |

Forest Garden | * | | | | * |

Maquoketa | * | | | | * |

| | | | | |

Arkansas | * | | * | | |

Newman | * | | | * | |

Poole Pride | *| | * | | |

Pottawattamie | * | | * | | |

Robinson | * | | | | |

Wild Goose | * | * | | | |

| | | | | |

Cheney | * | | | * | |

| | | | | |

Abundance | * | | * | | |

Burbank | * | | | * | |

Chabot | * | | | | * |

Engre | * | | * | | |

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.

Besides the plants discussed above various nondescript members of the

genus Prunus are used as stocks for cultivated plums under particular

circumstances or for particular purposes. Seedlings of Munsoniana plums

are supposed to be preeminently adapted for low wet lands. J. W. Kerr

believes that seedlings of _Prunus hortulana_ are excellent stocks

for native plums as they never sucker.[152] The Sand plum (_Prunus

angustifolia watsoni_) offers possibilities as a stock for dwarfing

larger growing species. According to Hansen,[153] who reviews the

literature and describes several experiments of his own, the western Sand

cherry (_Prunus besseyi_) dwarfs varieties worked upon it and has the

merits of being extremely hardy and of producing trees which bear early

and abundantly. As stated in the discussion of Subcordata, stocks of this

plum have been used on the Pacific Coast and discarded because it dwarfs

trees and suckers badly. According to Wickson,[154] the apricot and

almond are sometimes used as stocks for plums in California and in some

instances with considerable success.

Lastly, suckers are not uncommonly used by plum-growers for certain

varieties. Thus in the western part of New York, the plum-growing region

of the East, several varieties as the Reine Claudes and some of the

Damsons are propagated from sprouts taken from the base of old trees.

This method can be used, of course, only when the trees are grown

upon their own roots. The writer was told by plum-growers in Germany

and France that most of the plums in gardens and small plantations,

constituting the majority of the plums in the two countries, were

propagated from suckers. This method has small merit except that it

enables a grower to get a few trees cheaply and perhaps gives a better

tree of some varieties for a heavy soil. Beyond question it gives trees

with a tendency to sucker—an undesirable attribute.

In the horticultural literature of the time recommendations for

top-working plums are rather frequent. It is true that many varieties

of plums grow slowly and make crooked growths, especially in the

nursery, but in the attempts at grafting in New York the failures are

more conspicuous than the successes. If top-working is decided upon,

the earlier in the life of the tree it is done, the better. For the

Domesticas at least, the Lombard is probably the best stock. The method

of top-working is to graft in early spring or bud in late summer.

Grafting ought to be used more often than it is to renew the tops of

injured trees, as the difficulties in doing this are not much greater

than in the case of apples.

PLUM ORCHARDS AND THEIR CARE.

Plum trees in New York are set from twelve to twenty feet apart. The

amount of room given seems to depend mostly upon the custom in the

locality, though, as all agree, it should depend upon the soil and

the variety. The deduction which plum-growers are drawing from these

experiences is that the plum should have more room than is generally

given it, therefore, wider plantings are more the rule now than formerly.

Little attention has been paid to mixed planting for cross-pollination

in this State, as the Domesticas are planted almost exclusively and seem

under orchard conditions to be self-fertile.

In this region plum trees are usually planted two years from the bud, the

exception being the Japanese which are sometimes set at a year from the

bud. Plum trees in the past have been headed at three or four feet above

the ground but the tendency now is to head them lower—half the above

distances, and in orchards so planted there seems to be no inconvenience

in tilling with modern implements. In the commercial orchards of the

State the heads are formed of four or five main branches and in the

case of the Domesticas and Insititias about a central trunk but with

the Trifloras the leader is often removed leaving a vase-formed head.

After the head is formed the subsequent pruning is simple, consisting of

cutting out injured and crossed branches and heading-in long, whip-like

growths. The Trifloras receive more pruning than the European varieties,

as much of the fruit is borne on the growth of the previous season and it

is necessary to keep the bearing wood near the trunk. It is the custom to

cut rank growing Trifloras severely but the value of such a procedure is

doubtful, as the more such a plum is pruned the more it will need pruning

in the years to follow. A better plan seems to be to curtail the food and

prune as little as possible, though on rich soils the tree would probably

grow out of all bounds unless cut back somewhat year after year.

About the only cultivated native plums to be found in New York, if a

few Wild Goose trees here and there are excepted, are on the grounds

of this Station. Experience here demonstrates that, prune as you will,

certain varieties of the native species will remain crooked, ungainly and

unkempt. Pruning some varieties is necessary in order to permit pickers

to get into the dense, thorny heads; heading-in such varieties would make

their tops wholly impenetrable.

In common with all tree-fruits the best plum orchards are tilled. Such

tillage usually consists of plowing in the spring followed by frequent

cultivation until the middle of August, at which time a cover-crop of

clover, oats or barley is sown. The plum seems to require more water

than other tree-fruits—it often thrives in comparatively moist land and

fails on sandy soils where the peach would grow luxuriantly. Cultivation

to save moisture is very necessary for the plum in the experience of New

York growers. Grass and grain have proved ruinous in most orchards where

tried, though cultivated crops between young trees to pay for keep until

fruiting-time are very generally planted. The claim is made by some, and

with a show of reason, that there is less of the brown-rot in tilled

orchards than in neglected ones for the reason that the mummied fruits

which carry the fungus through the winter are buried by plowing and with

shallow cultivation, at least, do not come to light and life.

Plum-growers very generally recognize the several distinct and valuable

purposes which cover-crops serve in orchards. They protect the tree from

root-killing, from cold, keep the soil from washing, add humus and,

with legumes, nitrogen to the soil, modify the physical structure of

the soil and hasten seasonal maturity of the tree. There is one other

function which is not so often taken into account. Plum orchards in

which cover-crops are regularly grown, even though the crop be not a

legume, need less fertilizers than those in which no such crop is grown.

There are several reasonable suppositions as to why there should be such

an effect, but one not usually given sufficient consideration is that

cover-crops make available much plant food in the soil. Each plant in the

crop collects food from soil and air, most of it otherwise unavailable,

and turns it over to the trees.

A discussion of fertilizers naturally follows. Present practices in the

use of fertilizers with the plum, as with other fruits, are very diverse.

It is impossible to ascertain what considerations have governed the

applications of fertilizers in the plum orchards of New York or what the

results have been. Too often, it is to be feared, fertilizers have been

used as “cure-alls” for any or all of the ills to which trees are heirs.

Out of the mass of conflicting data as to the effects of fertilizers on

plums, the most apparent fact is that much of the fertilizers for this

fruit is wasted; this in face of the fact that plums want rich soils. But

the plum crop is mostly water, the foliage remains on the ground, the

trees grow several years before fruiting, their growing season is from

early spring until late fall, the roots go deep and spread far, the trees

transpire large amounts of water, hence may thrive on diluted solutions

of plant food, and now and then there is an off year in bearing for the

trees to recuperate.

It does not follow from the above consideration that plums never need

fertilizers, but it does seem plain that they need rather less than truck

or farm crops and that applications of plant food must be made with

exceedingly great care if fertilizing is to be done without waste. There

is a growing disposition on the part of plum-growers to experiment very

carefully and know that they are getting the worth of their money before

using any considerable quantity of fertilizers for their trees.

Thinning the fruit should be a regular practice with plum-growers, but

it is the operation in the growing of this fruit about which growers are

most careless both as to whether it is done at all and in the manner

of doing. Many growers in New York, realizing the great necessity of

thinning certain varieties of Triflora, as Burbank and Abundance, follow

the practice very regularly with plums of this group; but the Domesticas

are seldom well thinned, though some of them, of which Lombard is a

conspicuous example, ought nearly always to have anywhere from one-fifth

to half of the fruit removed. Growers of some of the native varieties in

regions where these sorts are grown say that under cultivation some kinds

of these plums will bear themselves to death if a part of the crop be not

removed in most years. Those growers in New York who thin, do the work as

soon as possible after the June drop has taken place.

HARVESTING AND MARKETING.

Plum trees in this climate begin to bear when set from three to five

years. The Triflora varieties will bear soonest, the Old World varieties

next in order, say at four years from setting, and the native sorts, as

a rule, come in bearing last. At eight or ten years of age, prolific

varieties of the Triflora and Domestica sorts bear in a good year about

three bushels of fruit; the Insititia and native varieties, on the

Station grounds, at least, do not bear as much, though most of the plums

of these two groups bear more regularly than the first named groups.

Plums in this State, and east of the Mississippi generally, are picked

and put upon the market just before they reach edible condition; while

farther away they must be picked much greener. It is the practice in the

East to pick while still somewhat green because the fruit so picked is

best handled at this stage of maturity and the brown-rot fungus is likely

to destroy much of the crop if left until fully matured. Some of the

Triflora sorts, Abundance, Burbank and October, for example, are picked

from a week to ten days before ripe and yet develop very good color and

flavor. The Domesticas need not be, and are not, picked quite so green.

In picking, great diversity exists as to ladders, receptacles, and manner

of conveyance from orchard to packing house. These need not be discussed

here, nor need the methods of picking be spoken of further than to say

that while good growers consider it vital not to bruise the fruit nor

destroy the delicate bloom, if such injuries can be avoided, pickers in

general are not nearly as observant of these important details as they

should be.

The plum crop is sent to market, for most part in New York, in six,

eight and ten-pound grape baskets with the preference at present for the

smallest of these baskets. Occasionally some fruit is packed in four

pound baskets. Rarely, and always to the disadvantage of both producer

and consumer, plums go to market in the packages in which the fruit

is picked. Indeed, it is seldom advantageous to pack the fruit in the

field, it being far better to convey it to the packing house where the

preparations for shipping may be more carefully made, as the package and

the manner of packing advertise the product. Plums coming to this State

from the far West are often wrapped individually in tissue paper as a

help in safe shipping and to add to their attractiveness but the fruit

grown in the State is seldom, if ever, so treated, though it is possible

that choice specimens could be profitably wrapped. Of the sorting,

grading, facing and marking the packages, little need be said except

that they are too rarely well done in present methods, though there is a

steady improvement in attending to these important matters.

Few plums are stored longer than a week at most in common storage and

three weeks or a month is quite the limit for most varieties in cold

storage. Late plums and in particular some of the prunes might well be

stored longer than is now the custom if proper precautions are taken, as

is shown by the experience at this Station where a considerable number

of the Domestica and Insititia varieties are annually kept in common

storage for a month or longer without unusual precautions. Some of the

new varieties offered to growers, as Apple and Occident, are recommended

as keeping for several weeks after picking. There is a most marked

difference in the keeping qualities of this fruit and it is certain that

varieties can now be selected for long keeping and that there is a fine

opportunity for breeding sorts that will keep even longer than any we now

have.

Marketing, the actual selling, is a business quite by itself, and since

it is one which has changed greatly in the past few years and is destined

to change even more in the near future, a few observations on the subject

are worth putting on record. A well developed local market is undoubtedly

the best selling place for the plum producer, as in it the sales are

directly to the consumer, eliminating expensive middlemen. The westward

spread of manufacturing industries, the workers in which use up the

western-grown fruit, is making better local markets for eastern plums, a

point worth noting, for many New York plum-growers have ceased planting,

indeed have been removing trees, fearing western competition.

By far the greater part of the plum crop now finds its way to consumers

through the following costly distributive system: 1st. Local buyers who

ship to centers of consumption. 2nd. Transportation companies. 3rd.

Commission companies who collect and distribute the crop in consuming

centers. 4th. Retailers who parcel out the quantities and the qualities

demanded by the consumer. The great defect in handling the crop is,

that there are too many men and too much machinery to do the work

cheaply—moreover, the risks of depreciation are great, and the fruit is

not handled on a large scale chiefly because of a lack of capital by the

grower or local buyer. These defects in the present distribution of plums

in New York make the price received by the grower about half that paid

by the consumer and the selling of the crop a more or less speculative

business. The plum industry, as is the case with all fruits, is greatly

hampered by the present marketing systems.

Unfortunately there is yet but a small outlet for surplus plums as

manufactured products. As a rule the commercial outlook is best for those

fruits of which the surplus can be turned into by-products. The only

outlet for the plum in the East is in canning, as this region is unable

to compete with the West in the making of prunes[155] and as the several

plum products of the Old World are not in demand in the New World. Beyond

question there are a number of products, as preserves, jellies from

the native plums, glacé fruits, plum butter, marmalades and the like,

which could be made profitable for the markets and thus a great help in

utilizing surplus plums.

DISEASES.

Plums are subject to a considerable number of fungus diseases, several of

which are often virulent, the virulence depending on locality, season,

weather and variety. Happily for the plum industry, knowledge of plant

pathology has made such advancements in recent years that nearly all of

the diseases of this fruit are now controlled by preventive or remedial

measures.

One of the commonest and most striking of the diseases of the plum is

black-knot[156] (_Plowrightia morbosa_ (Schw.) Saccardo) characterized

by wartlike excrescences on shoots and branches. In early summer these

knots are dark green, soft and velvety, but as the fungus ripens in the

fall the color changes to a carbon-like black and the knots become hard

and brittle. The disease is usually confined to one side of the twig

or branch so that death of the affected part does not ensue at once.

Black-knot is an American malady, at one time confined to the eastern

part of the continent where in some localities its ravages forced the

abandonment of plum-growing. The fungus is now endemic to wild or

cultivated plants in practically all the plum-growing regions of the

continent, but it is still epidemic only in the East, the South and West

being practically free from the disease. Unless especially virulent

black-knot is controlled by cutting out the diseased wood. Usually

eradication is not possible without several prunings during a season.

Much has been made of the supposed immunity of some varieties of plums

to black-knot. In the vicinity of this Station, where the disease is

always present and often rampant, the differences in immunity are not

very marked in varieties of the same species. The Trifloras are less

attacked, however, than any other group of plums, and the Insititias

rank next in immunity. No variety of the Domesticas has yet proved to

be free from the disease but strong claims are made that Middleburg and

Palatine are relatively free.

Next in order of seriousness among the diseases which attack cultivated

plums is the brown-rot[157] (_Sclerotinia fructigena_ (Persoon)

Schroeter) known also very commonly as the ripe-rot and sometimes as

peach-blight. The disease is most conspicuous on the ripe fruits of the

various drupes and is popularly supposed to be confined to the fruits

alone. Such is not the case, for it also attacks, and very vigorously

oftentimes, the flowers and shoots. The presence of the disease on the

fruits is known by a dark discoloration of the skin which is afterward

partly or wholly covered by pustule-like aggregations of grayish spores.

The decayed fruits may fall to the ground, or as is more usual in the

case of plums, they hang to the tree and as the juice evaporates become

shriveled mummies, each mummy being a storehouse of the fungus from which

infection spreads the following season. The twigs, flowers and leaves

are known to be suffering from inroads of the parasite when they are

blackened as if nipped by frost. In warm, damp weather the rot spreads

with great rapidity and fruits touching in clusters or in boxes stored

for shipping are well placed to spread the epidemic. Destruction of the

mummy-like fruits and all other sources of infection, and spraying with

bordeaux mixture are now practiced as preventives, but so far as the crop

is concerned with but indifferent success. A better remedy than we now

have is eagerly looked for by growers of fruits.

The hosts of this fungus show varying degrees of susceptibility to it,

the peach and the sweet cherries being more subject to it than plums.

Similarly, among plums some species and varieties are more susceptible

than others. Thus the Trifloras and Americanas, the latter especially

in the South, are injured more by the brown-rot than other species.

The idiosyncrasies of varieties in this regard are best shown in the

discussions of the individual sorts.

Several interesting and sometimes destructive diseases of plums are

caused by various species of the fungal genus Exoascus.[158] The most

common of these, and the most striking and destructive, is plum-pockets

(_Exoascus pruni_ Fuckel), which causes prominent deformities of

the fruit. These give the disease the common name or less frequently

“bladders” and “curl.” The fungus attacks the developing fruits at an

early stage of their growth and causes the production of a spongy mass in

the fleshy tissue which greatly enlarges and distorts the plum. The stone

in a diseased plum is but rudimentary or very often not at all developed.

Less prominently but quite as frequently, the leaves are attacked,

showing as they unfold more or less red or yellow with a very decided

curling and arching of the leaf-blade. The disease usually spreads from

the leaves to the shoots, the infected shoots with their rosettes of

mal-formed leaves giving the tree a most unsightly appearance. Prevention

at present consists of removing the diseased parts and spraying with

bordeaux mixture when the buds begin to swell. Munsoniana and Hortulana

plums seem to be most susceptible to this disease. Atkinson[159] has

described several species of Exoascus on the different species of wild

plums, some of which are liable to be found on the cultivated varieties

of the native plums. They are all very similar to _Exoascus pruni_,

differing chiefly, in the eyes of the layman, in forming smaller pockets.

Sturgis[160] records an attack of one of the leaf-curl fungi, distinct

from the plum-pockets fungus, on varieties of Triflora in Connecticut,

which seemed to him to be of scientific and economic importance.

The leaves of the different species of cultivated plums are attacked by

several fungi which produce diseased spots on the foliage, which for most

part drop out, causing a shot-hole effect. These diseases pass under such

descriptive names as “shot-hole fungus,” “leaf-spot,” and “leaf-blight.”

The fungus probably responsible for most of this trouble is best known as

the shot-hole fungus[161] (_Cylindrosporium padi_ Karsten). The Domestica

and Triflora varieties are very susceptible to this fungus, which, on the

foliage of the first, causes spots for most part, while on the latter the

spots on the leaves are nearly always followed by holes. Varieties of the

native species, especially those of Americana and Nigra, are relatively

free from this disease. Another of these shot-hole fungi is _Cercospora

circumscissa_ Saccardo[162], much less common than the former, but still

to be considered and especially on the foliage of Americana. All of these

diseases of the foliage are prevented to some degree by the proper use

of bordeaux mixture, which, on the Triflora plums at least, must be used

with great care to avoid injury. Cultivation has a salutary effect as it

destroys the diseased leaves which harbor the fungi.

Another disease of plum foliage, occurring rarely on the fruit, is the

plum-leaf rust[163] (_Puccinia pruni-spinosae_ Persoon) which produces so

considerable a number of spore cases on the underside of the leaves as

to give the foliage a brownish cast and to cause defoliation in severe

infections. The fungus is most apparent in the fall and most troublesome

in warm, moist climates. Bordeaux is used as a preventive.

Stewart and Rolfs have shown that trunks and branches of plums affected

by sunscald in New York are almost invariably infested by a fungus[164]

(_Valsa leucostoma_ Persoon) which in the Old World is known as the

“die back” of the peach. The disease manifests itself on plums chiefly

by affected areas much depressed at the boundary between the living and

the dead bark, these areas usually, not always, having connection with

sunscald injuries on the trunk. The disease is accompanied by more or

less gumming.

In common with nearly all rosaceous plants, in nearly all countries,

the plum is sometimes seriously injured by the powdery mildew[165]

(_Podosphaera oxyacanthae_ DeBary). The affected leaves have a grayish

appearance caused by the parts of the fungus which project beyond the

leaf tissue; when badly diseased the leaves are more or less arched and

curled. Mildew is seldom prevalent enough on plums to require treatment.

The crown gall,[166] (_Bacterium tumefaciens_ Smith and Townsend) is a

parasite on all of the fruits of the order Rosaceae and is especially

common on nursery stock, attacking plums in many soils but rarely,

however, to the great injury of the plant. These galls are perennial

structures of very varying duration. They are to be found on the roots,

usually at the collar of the plant, and vary from the size of a pea to

that of a man’s fist, forming at maturity, rough, knotty, dark-colored

masses. Means of prevention or cure are not established though all agree

that soils may be inoculated with the disease from infected stock; hence

the necessity of discarding diseased trees at transplanting time.

Smith found in Michigan and Clinton in Connecticut a disease of the fruit

called bacterial black spot[167] (_Pseudomonas pruni_ Smith) of the same

generic origin as the crown gall but widely different in nature. The

writers and the growers who found the infected fruit, saw the disease

only on the Triflora plums. It attacks the green fruits which show

conspicuous, black-purple, sunken spots sometimes as large as half an

inch in diameter. The injuries are usually isolated and quite superficial

but nevertheless, spoil the fruit.

The plum in common with other stone-fruits often suffers from an

excessive flow of gum, for which trouble the name gummosis[168] is now

generally applied. The disease is to be found wherever plums are grown

but it is much more destructive on the Pacific than on the Atlantic

seaboard. So far as is now known gummosis is secondary to injuries caused

by fungi, bacteria, insects, frost, sunscald, and mechanical agencies.

The disease is least common in species and varieties having hard wood;

on trees on soils favoring the maturity of wood; under conditions where

sun and frost are not injurious; and, obviously, in orchards where by

good care the primary causes of gumming are kept out. Stewart[169] has

recorded an interesting case of gum-pockets in the fruit, but could

assign no cause.

Mechanical injuries from the sun, frost and hail are troubles with which

nearly all plum-growers must contend at one time or another. In this

region the Reine Claude and Triflora plums suffer much from sunscald

but none are wholly immune, though Lombard is possibly most so. These

injuries from the elements of weather are often mistaken for diseases,

and are so often followed by fungal parasites and insects as to make

it difficult to distinguish the primary from the secondary trouble.

Low-heading of the trees is the best preventive of these trunk injuries.

Plums are somewhat subject to attacks of the well-known peach scab[170]

(_Cladosporium carpophilum_ Thumen). The scab appears in numerous, small,

sooty, circular spots of brownish color, often confined to one side of

a fruit but in other cases distributed over the whole surface. None of

the cultivated species are free from the disease but the Munsoniana,

and Hortulana varieties are most susceptible to it. Pear blight,[171]

(_Bacillus amylovorus_ (Burrill) DeToni) commonly thought of as a disease

of the pear and apple has been found on various plums, and the yellows of

the peach, cause unknown, is often quite destructive to Triflora plums.

According to Smith the peach rosette,[172] cause unknown, attacks both

wild and cultivated plums in the South and is quickly fatal. The disease

was prevalent on the wild Angustifolias, on two varieties of Triflora,

Kelsey and Botan, but the observer had not seen rosette on varieties of

Domestica.

Waugh describes a trouble which he calls “flyspeck fungus”[173] found on

fruits sent from the Southern States, in which small areas are thickly

dotted with black spots; also a fruit-spot on plums from Texas caused, as

he states, by an undetermined Phoma.[174] Starnes of Georgia describes a

malady of the Triflora plums called “wilt,”[175] cause unknown, which he

states is the most serious obstacle to the culture of this plum in the

South. In this peculiar disease the foliage passes directly from a green,

healthy state into a wilted and then parched condition, the death warrant

being signed when a tree is once affected. In Oregon and Washington the

Italian Prune is subject to a leaf-curl[176] which begins in mid-summer

and curls the leaves conduplicately without withering but shriveling

somewhat. As the season advances the leaves turn yellow and many of them

drop. Neither cause nor cure is known. Smith described a plum-blight[177]

of native plums in Georgia which “destroys large branches or even whole

trees in mid-summer in the course of a few weeks.”

INSECTS.

Cultivated plums furnish food for a great number of insects. Many of the

destructive insect pests of the several cultivated species of Prunus

are known to have come from the wild plants of the genus, but others,

and possibly the majority, come from over the seas. No less than forty

species of insects may be enumerated as pests of the plum and many

more can be counted as occasional parasites on one or another of the

species. Of the formidable pests the plum curculio is probably the most

troublesome. The plum curculio[178] (_Conotrachelus nenuphar_ Herbst) is

a rough, grayish snout-beetle somewhat less than a quarter of an inch

in length, an insect so familiar to fruit-growers as hardly to need

a description. The female beetle pierces the skin of the young plums

and places an egg in the puncture. About this cavity she gouges out a

crescent-shaped trench, the puncture and trench making the “star and

crescent” of the Ottoman Empire, hence the common name of the beetle,

“The Little Turk.” The egg-laying process may be repeated in a number

of fruits and from each egg a larva hatches within a week and burrows

to the stone, making a wormy fruit. Most of the infested plums drop. In

years past plum-growers relied upon jarring the beetles from the trees

in the early morning, but the treatment was too expensive, and poisoning

with an arsenate is now the chief means of combating the pest. Rubbish

and vegetation offer hiding places for the insects and hence cultivated

orchards are more free from curculio. Thin skinned varieties are damaged

most by the insect but there are no “curculio-proof” plums.

A larger snout-beetle than the curculio, the plum gouger[179]

(_Anthonomus scutellaris_ LeConte), occasionally does much damage to

plums. The work of the gouger may be told from that of the curculio by

the absence of the crescent cut about the puncture made for the egg, and

from the fact that the larvæ of this pest chiefly infest the stone and

those of the other insect the flesh of the plum. The remedies are the

same for the two insects though the gouger is more easily destroyed.

Among the several borers which are more or less destructive to species

of Rosaceae only the peach borer[180] (_Sanninoidea exitiosa_ Say.)

may be counted as a troublesome pest of the plum. The larvæ of this

insect are frequently to be found in both wild and cultivated plum trees

and must be combated in nearly all plum orchards east of the Rocky

Mountains. The prevention of the work of the borer is best accomplished

by thorough cultivation, the use of coverings of tar and poisonous washes

and mounding the trees. Destruction is effectively carried out only by

digging out the borer with knife or wire. The lesser peach borer[181]

(_Sesia pictipes_ Grote & Robinson) attacks the plum and in New York has

been found particularly injurious to the Wickson plums. The flat-headed

apple tree borer[182] (_Chrysobothris femorata_ Fabricius) is frequently

found in the wood of wild plums and is sometimes a pest of the several

cultivated species. It is treated as is the peach borer. The shot-hole

borer[183] (_Eccoptogaster rugulosus_ Ratzeburg) a diminutive insect

which deposits its eggs in the trunks or large branches of various

members of the genus Prunus, may be regarded as an effect rather than a

cause of disease, for it seldom injures perfectly healthy plum trees.

The peach bark-beetle[184] (_Phlœotribus liminaris_ Harris) is somewhat

similar in its work to the shot-hole borer and like it is found for most

part only in diseased and decrepit trees.

The plum aphis[185] (_Aphis prunifolii_ Fitch) is sometimes very

destructive to varieties of the native plums, especially the Americanas,

and occasionally injures or even kills the young trees of the Domestica

sorts. It is not a formidable foe in New York, and it is the exception

when trees must be treated for it, the treatment being any of the contact

solutions used against sucking insects. The cherry aphis[186] (_Myzus

cerasi_ Linnaeus) and the green peach aphis[187] (_Myzus persicæ_ Sulzer)

are much less common than the plum aphis on plum trees, but are sometimes

abundant on foliage of this fruit and are combated in the same way as the

more common aphis. Gillette enumerates two other aphids as attacking the

plum in Colorado—the rusty brown plum louse[188] (_Aphis setariæ_ Thomas)

and the mealy plum louse[189] (_Hyalopterus arundinis_ Fabricius).

Several scale insects infest the plum. Chief of these is the dreaded San

José scale[190] (_Aspidiotus perniciosus_ Comstock) known and feared by

all fruit-growers in the United States. The lime and sulphur solution

is now the most common and probably the most effective spray for this

insect. The European fruit lecanium[191] (_Lecanium corni_ Bouche)

occasionally does a great deal of damage in New York and now and then

destroys the whole crop in an orchard. The winter treatment for San

José scale is used to control this pest, but usually such treatment

is supplemented by a summer spray about July first with such contact

sprays as whale oil soap and kerosene emulsion. Of the other scales[192]

which feed upon plums and now and then become pestiferous the following

may be named: The fruit pulvinaria (_Pulvinaria amygdali_ Cockerell),

the mealy bug (_Pseudococcus longispinus_ Targioni), the scurfy scale

(_Chionaspis furfura_ Fitch.), the West Indian peach scale (_Aulacaspis

pentagona_ Targioni), the Putnam scale (_Aspidiotus ancylus_ Putnam),

the cherry scale (_Aspidiotus forbesi_ Johnson), the walnut scale

(_Aspidiotus juglans-regiæ_ Comstock), Howard’s scale (_Aspidiotus

howardii_ Cockerell), the European fruit scale (_Aspidiotus ostreæformis_

Curtis), the red scale of California (_Chrysomphalus aurantii_ Maskell),

the oyster-shell scale (_Lepidosaphes ulmi_ Linnaeus), and the soft scale

(_Coccus hesperidum_ Linnaeus).

Wild plums of several species seem to be favorite feeding grounds

for the tent caterpillar[193] (_Malacosoma americana_ Fabricius),

but cultivated plums are not so often attacked; the spraying with

arsenites usually given for the curculio is fatal to this pest as well.

The spring canker-worm[194] (_Paleacrita vernata_ Peck) and the fall

canker-worm[195] (_Alsophila pometaria_ Harris) are other caterpillars

which often do much damage unless checked by destructive measures, of

which the best are the arsenical sprays. The larvæ of a considerable

number of other moths and butterflies are often found on plum foliage but

seldom in such numbers as to require systematic destruction.

The eye-spotted bud-moth[196] (_Tmetocera ocellana_ Schiffermuller) is a

rather serious pest in plum nurseries where the larvæ eat into the young

buds at the time they are opening, often destroying the shoots. Sometimes

the larvæ are found destroying buds on old trees. The arsenical sprays

are used to destroy this pest. The peach twig-moth (_Anarsia lineatella_

Zeller) is now and then found in plum twigs but is seldom classed as a

plum pest.

The clover mite[197] (_Bryobia pratensis_ Garman) formerly considered a

serious pest of the plum only in the far West, is now abundant in plum

orchards in New York. It can be controlled by applications of lime and

sulphur. The bumble-flower beetle[198] (_Euphoria inda_ Linnaeus) is

reported by Goff to be occasionally very injurious to plums in Wisconsin.

Remedies seem not to have been tried. The larvæ of the cherry slug[199]

(_Selandria cerasi_ Peck) is not infrequently found doing damage to plum

foliage and occasionally the larvæ of one or two other saw-flies feed on

the plum. These are all overcome by the use of arsenical sprays. At least

one of the curious insects know as “case-bearers” attacks the plums. The

troublesome one is the pistol case-bearer[200] (_Coleophora malivorella_

Riley), which is not often a pest but has sometimes done considerable

damage. Attempts to check this insect with the arsenical sprays have

usually proved successful. The plum tree is a host-plant of the hop

aphis[201] (_Phorodon humuli_ Schrank). So much does this insect feed on

the plum that the destruction of plum trees in the vicinity of hop fields

is recommended to hop-growers by Riley.