This section of the book is from the Guide To Hardy Fruits And Ornamentals book, by Thomas Joseph Dwyer, published in 1903.
This comparatively new family has revolutionized plum growing for some years past. They are in many essential ways different and preferable to our European sorts. The trees are hardier and will endure neglect and unfavorable situations better; they are stronger and more vigorous growers, much more productive, and as a rule, will come into bearing from two to four years earlier. The fruits average considerably larger, carry and sell better in market. They are superior for canning and fully as rich in flavor, consequently just as desirable as a desert and in its natural state. We have fruited several hundred trees during the past three years, and it was a common occurrence to pick half a bushel of choice fruit from three and four year old trees of Abundance, Burbank and other varieties; this, too, after we had thinned out two thirds of the fruit from the trees. This thinning is of absolute necessity to get choice fruit and to keep the trees from breaking down with an overload of fruit. The fruit should be thinned when it is about the size of a walnut or about one4hird grown. To get the best fruit and avoid rotting, no two specimens should touch each other at any time.
-- This must be practiced yearly with a heavy hand. In fact it is next to impossible to get the average horticulturist to cut back these trees as they should be treated. As before stated, they are rampant growers, and such sorts as Burbank will make a wood growth of from six to twelve feet each season. If this is not kept in check it will soon make a large tree that will exhaust itself trying to mature a superfluous quantity of fruit, inconsistent with its age and capabilities. Then this heavy annual pruning and heading back, is of itself somewhat detrimental to the welfare of the trees therefore, in the case of these Japan Plums, we would suggest and advise Summer and early Autumn pinching back of the leading and lateral branches; just when and how to do this must be determined by the variety and the growth it has made.
-- The best food for these Plums is that heretofore recommended for the peach; unleached wood ashes, nitrate of soda, pure ground bone and any good make of complete fertilizer. Stable manure can be used sparingly, otherwise we will get an overabundance of wood.
-- This should be properly looked after, using the Bordeaux mixture as heretofore recommended. Spraying and thinning of the fruit is of primary importance, as they both are necessary as preventatives to the rotting of the fruit, especially in moist and otherwise unfavorable seasons. We want to urge the advisability of heading these trees quite close to the surface of the ground, not over two feet, or about the same as the Peach tree. This method, is of necessity to make the trees strong, solid and bulky near the roots, to prevent injury from high winds, heaving, overbearing and other causes.
* Distance Apart
-- For commercial orcharding, Plum Trees should be planted twenty feet apart each way. In the home orchard they may be planted twelve to fifteen feet apart. By a little extra pruning back they can be fruited at these distances for a number of years, and in fact indefinitely without interfering. By keeping them in semi-dwarf state we will get large, choice fruit.
* The Right Soil
-- The Plum will grow and thrive on a great variety of soil, but as a matter of fact it attains its greatest perfection on heavy, loose, pliable land. It is a fact that the trees live longer and bear longer and more regularly on this character of ground. The Japan Plums have never failed us on any soil, and we have grown and fruited them with satisfactory results on all kinds of land, except the pure sand. The trees will not thrive on wet ground.
* Black Knot
-- This is one of the Plum's greatest enemies. Happily the Japan Plums are not as susceptible to it as the European varieties, in fact the writer's trees have been quite immune from it, yet we find that occasionally it does attack the Japan varieties. The only way, of course, to cope with this disease is to cut off, remove and burn the parts thus affected as soon as the knot is perceptible. Be sure to cut some distance say three or four inches, beyond the visible trouble. The Black Knot is a rough swelling of the wood, obnoxious looking, readily discernible and easily eradicated when taken advantage of in its early stages of development For several years before the introduction of the Japan Plums, this disease was so prevalent on the European Family of Plums, that their cultivation was quite generally abandoned, except by a few of the large fruit growers: throughout the country and especially in Western New York, where the production of this fruit is one of the leading industries. However, a better and much more encouraging feeling exists today, and the Plum is grown more largely than ever before in the history of the country. A good preventive against Black Knot is thorough cultivation. Trees that are neglected are quite generally infested with this fungous growth.
* The Curculio
-- This is another enemy of the Plum, fortunately, however, this can be easily and cheaply controlled. It is a small, dark brown beetle that stings the fruit, causing it to drop from the trees. When the trees blossom, and as the fruit begins to set, dress the ground about the Plum trees, make it very clean and smooth. Then, as soon as the Curculio commences its operations., spread a large sheet prepared for the purpose around each tree, and jar it so as: to shake down all fruits that have been stung, as well as all the Curculios. Both insects and stung fruits should be destroyed. This. work is performed daily, and ensures a full crop. The work is done quickly; a dozen trees in a garden can be attended to daily in less than half an hour's work of a man. Let those who really desire to grow fine crops of delicious Plums try this system, and follow it up rigidly, and they will be successful. You will find this insect much more prevalent some years than others. It is not at any time a difficult job to cope with it.