This is a process of layering by uniting a limb or branch of one tree or shrub with that of another of the same species or a nearly allied one. This quite frequently happens in the primitive forests probably by the twisting together of the tops of young trees by animals. Fig. 21 shows an example of this kind, where two oaks are thus united, forming one tree. In Europe it is common to unite the tops of two elms standing on opposite sides of a gateway, forming a common top over the centre of the opening. Inarching is often useful on the home place. As instances we may have a very hardy wild rose or a strong plant of Rosa rugosa standing beside a desirable garden rose. If a branch of the tender variety is brought in contact with one of the rugosa, with the bark of each shaved off where they meet, the two will unite if the point of union is waxed or covered with waxed paper to exclude air. But indoors the two cut surfaces will unite without waxing by merely binding them together with raffia or woolen yarn. After uniting, the top of the stock is cut away and the desired top saved, as shown in Fig. 22, where two potted plants are inarched.
In amateur practice it is a good way to get our best varieties of the grape on wild stocks. In German school yards the writer found low-branched cherry-trees with many wild-cherry stocks planted beneath. In June when new wood was rapidly forming the children were taught to inarch twigs of the cherry on the wild stocks beneath, where they stood until the next spring, when each student claimed his own tree to plant on the home grounds. It is the most certain way yet found by the writer to graft young stocks of the shellbark hickory, chestnut, oak, and English walnut, where the seedlings are in pots. In Prance and other parts of west Europe the writer has observed some queer effects produced by inarching. In gardens every branch of fruit-trees was inarched on one of neighboring trees in such a way as to form fanciful designs and arbors beneath. Indeed, whole groups of trees had a common circulation of top and a common support from the roots. In Europe inarching is also much used by amateurs in filling in naked spaces, in peach- and nectarine-trees. Even on vines mammoth bunches of grapes are formed by inarching bunches together, often of different colors of fruit. This, under glass, is done as soon as the berries are set.
Fig. 21. - Natural inarching. (After Bailey.)
Fig. 22.—Inarching two potted plants.