The most important shrubs commonly propagated by this means are Clematises, Roses and Rhododendrons. In the case of the first, the variety of Clematis to be propagated is attached to a piece of root of one of the commoner species, such as Viticella, Flammula, or lanuginosa. These species, raised from seed, have a tufted rootstock somewhat resembling that of Asparagus in their third year, and one plant will yield enough material for many plants, as pieces of two or three inches long suffice. A plant of the variety to be increased is grown in a pot and started in a warm house in winter and when it has made a few feet of growth the shoot is cut up into pieces between the joints with leaves and dormant buds. The soft tip is rejected. Sloping cuts are made on both root and shoot of the same length, so that they fit close together; this is splice grafting; they are then tied and inserted in small pots of sandy soil, the tip with its leaves just above the soil. Half loam and a quarter each of leaf-mould and sand make a good compost. Some propagators slit down the centre of the root cuttings, pare down the scion into the shape of a wedge, press it into the cleft in the root, tie and pot. This is wedge-grafting. In either case the pots should be kept close in bottom heat till rooted.
Although Roses are generally propagated by outdoor budding in gardens, large quantities of plants are raised by grafting in the nurseries, and this is done in heated houses at mid-winter. The varieties to be increased are grafted on to Brier stocks, generally seedling Briers, which are grown in pots for the purpose, because they can be put into heat and given a start at any time. They will be ready for grafting in a fortnight. The scions are small pieces of firm wood and they are attached to the side of the stock (1) by plain splice grafting, as in the case of Clematises, (2) by whip (tongue) or (3) by veneer grafting. A whip graft differs from a plain splice graft in that a tongue is raised by a second cut in both stock and scion. A veneer graft is one in which a shallow slice is taken off the stock with a small "butt" at the bottom, which takes the base of the scion. A slice is taken off the scion to correspond. Many would call this "side" grafting, as the scion is, as it were, let into the side of the stock, near the soil, not put on to the top of the stock. In each case the grafts are tied in and kept close in a warm case until the parts are united. No wax or clay is used as in outdoor grafting
With respect to Rhododendrons, they are mostly grafted on to R. ponticum. In this case the saddle graft is often used. The stock is cut wedge-shaped, and the scion is split and fixed on. But wedge-grafting and side-grafting (see above) are also practised. If the work is done in winter it is well to put the grafted stocks in moist but not strong heat. In spring they could be put in a pit or frame without heat, and this suits all the hardy varieties. The variety Cunningham's White is used as a stock for Indian Azaleas, being raised from cuttings in moist heat in winter and grafted the following year.
It is convenient to grow stocks for grafting purposes in pots for several months before operating, but they need not be put in heat until about a fortnight before the work is done.
Like Roses and Rhododendrons, various conifers and Cytisuses may be grafted in late winter or early spring.
The following subjects may be grafted:
Chionanthus (on Ash).
Most of the foregoing are cases in which garden varieties are grafted or budded on to a species.