This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Many plants are propagated by inserting a short shoot in a root of a relative or by side grafting. Most of the Tree Paeonies are raised by inserting a shoot in a cleft of a tuberous root of Poeonia officinalis, making the edges fit flush on one side, and then tying them up with raffia, etc. Shoots of Wistaria are also inserted in the fleshy roots of the same plant, as shown in fig. 82, while garden varieties of Clematis are grafted in thousands on the roots of the common G. Vitalba.
This method of propagation was, no doubt, suggested originally by the fact that boughs of trees that rub against each other and wear away the bark become united later on by means of their cambium layers. Inarching is thus a kind of grafting, but differs in that each of the plants to be united is growing on its own roots. It is often practised on Vines. A shoot of a desirable variety is cut and tongued on one side to fit into a similar cut and tongue on the undesirable one that may be worth retaining on account of its state of development, and to avoid replanting and remaking of the borders. When the inarched shoot has become firmly united it is severed from its own feeding base, while the stock to which it is attached has the portion above the inarched scion also cut away, thus leaving the lower portion of the stem and the roots. In this way a new variety takes the place of the old one without much trouble.
Bottle grafting is a form of inarching, and has been practised in connection with Oranges, Vines, Oleanders, and other woody-stemmed plants. A ripened shoot is taken, say of a Vine, about 1 ft. long. It is cut about 4 or 5 in. long, and tongued on one side about the middle, to fit into a corresponding cut and tongue on the stock. It is tied on securely, but the base of the shoot is stuck into a bottle of water. The latter should be replenished from time to time, fresh rainwater being preferred, and a few lumps of charcoal may be put in to keep it fresh for a longer period. [J. W.]
Fig. 82. - Root Grafting Wistaria.
A, Shoot inserted in root B and tied.