Sometimes called two-arm upright cordons
The U-form classifies somewhere between the cordon and the espalier. It consists of two upright branches joined to a single trunk below by an arc of a circle. The fruit is all borne on the two parallel stems which are treated essentially the same as upright cordons. (Fig. 17.)
The double U-form is made by growing two U's from the same tree. The stem is first divided near the ground into two branches and each of these is immediately divided into two more. The tree thus provides four parallel and equally spaced upright and fruiting stems equal to four upright cordons, except that they are all supported from a single trunk. The U- and double U-forms are employed mostly for plums, apricots, peaches and nectarines.
One occasionally sees much more elaborate schemes of training than any here mentioned. There are complex geometrical designs, even pictorial figures—birds, dogs, and beer-steins—and sometimes the initials of the gardener, or the name of his kingly and imperial majesty. In every case the method of producing these forms is practically the same. A frame is built of wood or wire in the form which it is desired to give the tree. Branches are developed at suitable points on the tree and these are tied out while they are growing to the wooden or metal form. It does not require any special care or ingenuity to produce the most elaborate designs in this method. It is essentially a job of carpentry.
FIG. 17—APRICOTS IN U-FORM
We come now to the cordons. If we take the simplest form, namely the upright cordon, we have what we may call a tree of one dimension only. The upright cordon has nothing but height, eschewing both breadth and thickness. A cordon is simply a tree trained to a single stem and this stem may be placed in any position. The position or direction of the stem classifies the cordon. There are, therefore, besides the upright cordon, others which are oblique, that is, which make an angle with the horizontal, those which are horizontal, and those which are bent into various forms. The serpent form is one of the simplest of these. This form of cordon is simply bent back and forth against a trellis forming a series of S's one above another. The horizontal cordons are of two varieties, namely one-arm and two-arm forms. It is altogether a matter of convenience which one of these forms is chosen.
