PLANNING AN IDEAL PLUM OR PRUNE
THE REQUIREMENTS AND HOW THEY MAY BE MET
When I was in the nursery business a woman came to me on one occasion and wanted trees for his orchard. I showed him my stock, but it did not suit him. He wanted trees that grew six feet high before branching. I had nothing answering that description, so he bought elsewhere. In a year or two his trees were sweeping the ground, quite as might have been expected. So the orchardist came to me to find out what he should do. Naturally I told him he should have commenced right by getting trees of the right form at the outset. Now there was nothing for him to do but to cut his trees back to the right height, and let them start anew, thus losing two years of growth. He did not like this prescription, but he presently had to follow it. Of course his trees were never as good as though they had been given the right start; but their new condition was an improvement on the old one. This misguided orchardist was simply acting on the mistaken idea that was everywhere current until quite recently-the idea that it is necessary to run a tree into the sky so that other crops can be raised under it, and that teams can be driven close to the trees in cultivating. Nowadays the orchardist adapts the implements of cultivation to the tree, instead of adapting the tree to the implements. Or, what is better, he adapts the trees to the land and makes the orchard pay better and with less labor, without attempting to raise any other crops in the orchard. It has been discovered that skyscrapers in the orchard do not pay. A tree should be of such form that the fruit may be picked conveniently. It should not be necessary to use step-ladders to gather the fruit from the lower branches. In the case of the prune, in particular, a low-branching tree is especially to be desired, that the prunes may not get bruised in falling for even as tough a fruit as a prune may be injured in falling from a tall tree.
PLANNING THE PLUM ORCHARD
The old way of planning an orchard was to look over a catalog and order half a dozen of this or half a dozen of that, without asking any questions or gaining information as to whether the varieties selected were adapted to the region where they were to be grown. And the old way for the grower or nursery man was to accept the form of the tree as it tended to grow, with little or no attempt to change it. But the new way is for the intending orchardist to select his varieties with the utmost care, paying careful heed to questions of soil and climate, and introducing only such fruits as are adapted to the conditions that must be met. And as to the trees themselves, when they begin to grow, the modern plant improver is by no means content to leave everything to Nature. He takes a hand from the outset, and largely determines the form of the tree. Moreover, the up-to-date orchardist will look beyond the existing variety, and recognize that it requires both imagination and labor to produce the ideal tree. Building an ideal plant of any kind is like building a house. Each must be planned in accordance with a clearly conceived idea. But there is this great difference: In the case of the plant you must wait for Nature to supply you with the material with which to build. Plant building is architecture-but architecture with limitations. It is always slow and very often it is extremely disappointing, yet it has its encouraging surprises as well. Times without number I have been ready to give up an attempt to secure an improvement on which I had worked unsuccessfully for years, when, just as my patience was at the breaking point, Nature would seem to have a generous mood and, as it were, throw the desired characteristic into my lap. What the blue print means to the architect, the conception of the tree or fruit or flower wanted should mean to the plant improver. It represents a precise ideal toward which to work, and it gives standards of comparison by which progress may be checked as the work progresses. In the case of the plum, it is possible to present the ideal to the mind with great accuracy. Of course it may not be possible to attain results strictly in accordance with the plan. But usually the ideal may be at least approximated if it has been intelligently conceived, and if it is persistently borne in mind.
SPECIFICATIONS FOR AN IDEAL PLUM
Let us now note specifically and in sequence some of the practical points to be considered in planning our ideal plum. In so doing we shall find that there is a certain amount of overlapping, or perhaps we had best say interference, of qualities. A plum that is best for one purpose may not be best for another. We must bear in mind the different purposes to which a plum is put, and endeavor to make our plan comprehensive enough to cover all of them. There are certain qualities, to be sure, that are desirable in every variety of fruit. Large size, for example, and frost-resisting quality are seldom or never disadvantageous. Yet even this must be qualified, for, in case of a prune, drying becomes more difficult as the fruit enlarges, and unusual size may be a disadvantage. But for plums in general we aim at a tolerably definite combination of qualities-size, form, color, flavor and hardiness-and endeavor to associate these in the same fruit. Taking up our ideal plum tree part by part, let us first consider the root. This is of great importance. A great difficulty of the French prune is that its root system is ordinarily inadequate. It is usually necessary to graft this prune on other roots. Peach stock is sometimes used to advantage both for this and for other varieties of plum. But there are some plums that do not graft kindly on the peach, and it is necessary in such cases to make a double graft, using first a cion of some plum that grafts well on the peach, and then grafting on this the cion of the desired variety. This is obviously a rather tedious procedure. Fortunately it has been discovered that the Myrobolan plum furnishes good roots on which almost all plums may be grafted, and this stock is becoming very popular. The roots of the apricot are also sometimes used successfully. On deep, dry soil, almond stock often gives the best results. But, of course, there will be great advantage if the plum can be made to grow a good set of roots of its own. It should be recalled that an abundance of roots is always closely correlated with abundance of foliage. One may tell at once in the orchard whether a tree has a good set of roots by observation of the foliage. And the close dependence of the roots on the foliage is a matter of common observation. Many orchardists fail to realize how completely the roots are governed by the amount of foliage. And even when this is realized the observed conditions are not always correctly interpreted. If the foliage did not govern the roots, our orchard trees would be of all sizes and of all degrees of vigor, whereas now, when grafted on seedlings of varying degrees of vigor, the trees are uniform. As to the stem of the tree, this should come up straight as a flag-staff, and should branch sturdily, the branches coming out not quite at right angles but turning slightly upward. Branches should not turn down, nor should they be crooked. Moreover, the branches should not tend to grow too long and slender. Many seedlings tend to take on a bushy growth, which is undesirable. Others are too slender. Some have a general irregularity of growth, which is particularly objectionable. Brushiness invariably indicates a lack of production; it suggests a reversion to some inferior ancestral type. And it may fairly be predicted that the tree will show similar reversion as to fruit, producing a small fruit of poor quality. Brushiness is indicated by slender, too abundant, poor branches instead of sturdy branches. Slender branches can never be correlative with large fruit-they have not requisite strength. That is one of the many reasons why I select seedlings with large branches, and those having prominent buds and large, thick leaves. These are all indications of a bearer of large fruit. Large branches and large fruit are associated together through the effect of past heredity; just as, contrariwise, small fruit and small leaves and branches are the hereditary traits that are similarly associated with small fruit. Of course, it is not always possible, in the present stage of orchard development, to secure a tree of perfect growth and form. This is true not alone of plums but of other orchard fruits. Some of our best varieties of orchard trees, like the Bartlett pear, have branches too slender and upright, and do not carry the fruit well. The Bellflower, though a fine apple, makes a weeping growth. The Newtown pippin makes too slender and upright a growth. On the other hand, the Gravenstein apple makes a very fine, spreading tree, and the popularity of this variety may be to some extent associated with the almost perfect form of the tree itself. But it is one thing to observe that a tree is imperfect, and quite another thing to take the trouble to improve it. We know that the branch system should resemble a vase in form, avoiding brushiness, woodiness, or overgrowth. But many orchardists who are well aware of this will not take the trouble to prune the tree in such a way as to encourage this development; nor will they consider the matter of selecting a variety that tends to grow in the right way without pruning. As to the leaf system, it is always desirable that the foliage of a fruit tree should be large, thick and abundant. In the case of cherries it is particularly desirable that the leaves should hang over the fruit to protect it from the weather and from birds. With the plum this is not so necessary. Still the question of foliage should always be considered. Other things being equal, seedlings should be selected that show large, thick leaves.
BLOSSOMS AND FRUITING
It is almost axiomatic to say that plum seedlings should bear perfect blossoms in reasonable abundance. The blossoms should be borne on the larger wood of the tree rather than on the tips, because the fruit is held better where it has the support of the older wood. Moreover, if the fruit is borne at the tips of the branches, these are brought too near the ground. The time of flowering should be given careful consideration in connection with the climate where your orchard is located. Many fruit trees bloom so early that in mild climates the late spring frosts injure them. In general, late-blossoming trees have an important advantage. It should be understood that a tree that blossoms late usually matures its fruit early, whereas one that blossoms early will usually bear late fruit. This is, of course, precisely the reverse of what might be expected, unless we bear in mind the reasons for the difference. A moment's reflection makes it clear that late bearing and early fruiting should be correlative, being adaptations to a climate where the summer is brief. The bearing season of the plum may be short or long according to the use to which the fruit is to be put. Fruit that is to be gathered wholesale for the market should have a short season, the major part of it ripening at the same time. On the other hand, fruit for home use or a local market should have a long season. But even more important is the matter of "every year bearing." A tree that never makes a failure-one that bears annually and does not have any off years-is the kind of a tree that is needed. The orchardist naturally wants a tree that can be depended upon to give him a crop. A tree that sometimes balks after starting a lot of fruit, because the temperature or conditions of moisture are not just to its liking, is not the kind of tree that endears itself to the fruit grower. It must be understood, however, that fullness of bearing has no necessary association with hardiness. The two qualities are quite distinct. A tree may have one quality and quite lack the other. It may be able to thrive under adverse conditions but not to bear under adverse conditions. The ideal tree, of course, is one that will not only thrive but will invariably produce a fair crop of fruit whether the season is hot or cold, dry or rainy. A fine practical test of fullness of bearing is supplied when a frost comes just after the blossoms have dropped, while the miniature fruit is fully exposed. A tree that will stand this test may generally be depended on as an every-year bearer. Nowadays the plant developer has this matter of every-year bearing in mind, and varieties of plums have been developed which conform to this business principle. Our fathers pretty generally supposed that a fruit failure about every second or third season was to be expected. Now we know that the right variety of fruit can be depended on to give a crop each season. In selecting stock for your prospective plum orchard, bear this point very carefully in mind, and choose only such varieties as have the inherent tendency to bear fruit with regularity.
SIZE AND QUALITY OF FRUIT
It was just noted that a prune may be so large that it dries badly. This is not likely to be the case, however, if the prune ripens early and has a high sugar content. And as to plums in general, large size is, of course, a foremost merit. There are other fruits that sometimes tend to grow too large. This is true of certain pears; also of some peaches. But the plum has not as yet been developed to anything like the maximum size, notwithstanding the very great improvement of recent years. A good many of my newer plums are giants in comparison with the standard plums of a generation ago. But no one complains that they are too large. On the contrary, their high price in the market is due in considerable measure to their large size. In selecting the ideal plum there is no reason nowadays why you should not secure one that bears fruit that is at least two inches in diameter on the average. In form the plum should approach the globular. This is best in most fruits, for the reason that the spherical form is the most compact, and therefore the one best adapted to handling and packing. The suture in the plum is a mark of recognition, but of no value to the fruit in any way. It is mostly due to the fact that one side of the plum grows slightly larger than the other. But this is a matter that concerns the pomologist rather than the fruit originator or grower. The same is true of the ridge on the plum stone. It is a mark often used as a distinguishing Character between different varieties, but which has no practical significance. The plum should be of some attractive color, red, yellow, or even a brilliant white. Green fruit is never attractive. It would appear that the birds and man have combined forces to produce red and yellow fruits by selection, because these colors are enticing, and we have come to associate them with superior qualities of fruit. The skin of the plum should be thick and firm, especially if the fruit is to be shipped to a distant market. For home use or a nearby market a thin-skinned plum may be quite as satisfactory. The bloom of the plum adds to its appearance, and its condition may be a test of freshness. The bloom evidently had originally a protective function, possibly shielding the fruit from the sun, or otherwise protecting the juices from too rapid chemical change. The bloom may be developed on a fruit by means of selection where it is especially desired for any reason. It is obviously only a minor characteristic of the perfect plum. The flesh of the plum should be firm, particularly if the fruit is to be used for shipping purposes. The texture may be shown by cutting the fruit with a dull knife. For home consumption, plums that are very watery are often considered a great treat. I have some splendid watery plums now growing-fruits that almost melt in the hand. But these have not the texture to stand the trip to market and keep in good condition. The orchardist must bear this difference clearly in mind, and let the choice be determined by the use for which the fruit is intended. Nearly white is usually the most suitable color for the flesh of the fruit. Yellow flesh is also admissible, and sometimes pink or crimson. The plums with crimson flesh, as we have elsewhere learned, are all descendants from the Satsuma plum which was one of my earliest importations from Japan. Plums show almost every possible combination of flavors. Appearances are sometimes deceptive as to the eating qualities of the fruit. As an instance, one plum that I have named the "Fraud" is extremely beautiful to look at, but its flavor is that of vinegar. There is, of course, a great range of variation between different plums-even aside from those that rank as prunes-in the matter of sugar-content. Some are very sour and require a great deal of sugar when cooked; others require almost no sugar, except possibly to bring out their flavor. Taste and aroma are so closely associated that they may be said to be almost identical. They simply represent the same thing as interpreted by different organs of sense. It is obviously desirable that a market fruit should have an attractive aroma, for both market man and customer often judge the fruit by this quite as much as by the taste. Closely associated with the flavor of the plum is the matter of a chemical content that will resist fermentation. A fruit that is too juicy and does not contain enough sugar will ferment very easily, as we have seen in connection with our studies of the prune. Some plums are peculiarly subject to fermentation, particularly if bruised in any way. Plums that contain plenty of sugar are, as we have seen, resistant to fermentation. This is one reason why prunes have gained in popularity for shipment in the fresh state to the eastern plum market. There is a good field for investigation as to the particular qualities, in addition to sugar content, that tend to make a fruit resist fermentation. In general it is observed that insipid fruits decay first. Highly flavored acid fruits as well as very sweet ones tend to resist fermentation. But the precise chemical conditions that have to do with this very important property of resistance to decay have been but little investigated. All that the prospective orchardist can do at present is to select varieties of fruit that have been shown to have good marketable qualities. Finally, there is the matter of the stone. In the case of the very soft plum, the stone may serve a useful function in giving support to the fruit. But the stone may be somewhat smaller than it commonly is and still give adequate support. In the development of stoneless plums it will be necessary to bear in mind that the removal of the stone to some extent takes from the fruit its natural support, and the plant developer will select with intent to increase the firmness of the pulp of the fruit. Where the stone is retained it should be free, particularly in the case of the plum. The advantages of a free-stone fruit are obvious to every fruit eater. Varieties of plums have been developed in which the stone becomes practically detached from the fruit on ripening. There is now no reason why the orchardist should not include free-stone among the qualities that he demands of his ideal plum. If to these qualities of root and branch and leaf and flower and fruit we add the one comprehensive requisition that the texture of tree and fruit alike should have the undefinable quality that makes it resistant to disease, we have perhaps summarized in broad and general outlines the most essential qualities of the ideal plum. It may properly enough be said that no plum hitherto developed can measure up to the maximum or ideal standard as to each and every one of these qualities. The production of a variety that will meet these requisitions remains for the plant improver of the future-perhaps of the not distant future. Meantime it will, I think, be admitted by those best competent to judge that there are some of my hybrid plums, notably, for example, the Wickson, the Formosa, and the Santa Rosa plums, and the Sugar, Standard and Conquest prunes, that, in their respective fields, make a fair approximation to the ideal standard. There are plums in the orchard that excel all these in some respects, but have not as yet all the qualities in combination.
-Building an ideal plant of any kind is like building a house. Each must be planned in accordance with a clearly conceived idea. But there is this great difference: in the case of the plant you must wait for Nature to supply you with the material with which to build.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 5 Chapter 6