Grafting and budding are means of propagation not previously described. They are propagative methods for most fruit tree varieties and for ornamental woody plants that do not come true from seed and the cuttings of which do not take root easily.
A grafted tree consists of two parts, scion and stock. The scion is cut from a twig of the variety sought to develop, and it is from the scion that the stem of the plant is to be developed. The stock is the part from which the root system is to be developed. It is usually of the same or a closely related variety. A cross cut through the trunk of a tree would reveal various layers, one of which, the cambium, is the thin layer of cells between the wood and bark from which new tissues grow. The union of stock and scion must bring the cambium of each together until the two parts have united in growth.
In budding, a single bud is used instead of a scion, and it is done during the growing season, whereas grafting usually is undertaken with dormant scions, in the spring or winter.
An ideal stock would be adaptable to climate conditions in which it will grow, as hardy as the variety grafted onto it, insect and disease resistant, reasonable in cost, and capable of easy propagation.
Wood for the scion usually is of one season's growth, usually taken from bearing trees, and the best of such wood is twigs that have grown vigorously a foot or more in the last season, although well matured, but shorter twigs frequently are used with success. Scion wood should not be cut when it is frozen. It is generally cut after the leaves have fallen in late fall or winter, and if it is not to be used at once it should be packed in moistened spagnum moss or sand and kept in a cool place.
The names of grafts usually indicate the position on the stock at which the union is effected. Root grafts are made on mature root tissue, stem grafts high on the stem, crown grafts on the stem near the ground, and top grafts on the branches. They are further classified according to the technique used in making the union, such as whip graft, cleft graft, splice graft, veneer graft, and bark graft.
If stock and scion are almost similar in size, the whip graft is especially useful. Assume that a 3-inch piece of root is used as the stock and a scion 3 to 8 inches long is selected. Holding a thin-bladed, sharp grafting knife diagonally to the stock, cut the lower end of the scion on an angle with one stroke, leaving a flat, oval surface between 1 and 2 inches long. About a quarter of the way from the tip of the cut slice a cleft in the cut surface, leaving a thin tongue.
Cut the upper end of the stock the same way and fit them together, making sure that the cambium layers of the two are together on one side at least. They then are tied together with light twine dipped in melted grafting wax, drained, and cooled. Tie the two pieces together firmly but not so tightly that the twine cuts the bark. When the winding has been completed the twine may be broken off and will stay in place without being tied. Do not use twine so durable that it will not decay in time to avoid constriction of the graft after growth starts. A light tape bandage may be used instead of twine.
The grafts then should be bundled in boxes of moist spagnum moss or sand and stored in a cool place with a constant temperature of just above 40 degrees. Examine them from time to time for mold, and, if it appears, unpack them and expose them to the air for a while before returning them to clean, drier packing. Presently, a callus, consisting of a spongy growth, will be seen to form along the edges of the juncture.
As soon as the ground can be worked, in early spring, the graft should be planted, while still dormant, putting the whole union and all of the scion except the top bud under ground. Plant in rich, well-drained soil, packing it firmly around the roots. Keep the planting clear of weeds and when lateral shoots develop pinch them out, without disturbing the main stem leaves, to throw all growth into the terminal bud until the main stem attains a height of about 30 inches.
When the stock is larger than the scion the cleft graft frequently is used, carrying out the operation usually while both are still dormant, in late winter or early spring.
The stock is cut off and a cleft notched in the surface, a slender, V-shaped cut of the sort a broad chisel would leave. The tool is held in to keep the lips apart. The scion usually is long enough to carry three buds. The lower end is cut to a flat point, the tool removed from the notch in the stock, and the scion inserted in its place. When the tool is removed from the cleft in the stock its sides are free to press against the scion where the cambium layers meet. If the stock is sufficiently thick, a scion may be set at either edge of the cleft, creating two chances for a good union. The pressure of the stock cleft should be sufficient to hold the scions without tying but all cut surfaces should be covered with grafting wax. If both scions take, one should be removed within a year or two. Bark grafts should be done in the spring, after the sap rises to allow the bark to be separated easily from the wood, but while the scions are still dormant. Stocks should be larger than scions. The stock is cut off and from its edge a downward cut about 1 1/2 inches long is made in the bark. The lower end of the scion is fashioned into a shoulder, halfway through the thickness and then down to the tip, so that the two cut surfaces in the scion form a right angle. The prepared end of the scion is then slipped under the bark, wrapped with twine, and sealed with grafting wax to keep the air out.
Grafts of evergreens and some deciduous trees for landscape usually do not succeed outdoors because of slow union. Most evergreen grafting must be done in specially equipped greenhouses and is not an undertaking for unskilled gardeners. One of the most frequently used evergreen grafts is the veneer graft, with the junction made in the stem of the stock just above the surface of the soil in which the plant stands. A narrow wedge is sliced down the stem about an inch long. The lower end of the scion is trimmed to fit this slot. After the scion is inserted, the union is bound with twine dipped in grafting wax, but no other wax is poured over the juncture. The grafted plant must be kept free of fluctuating temperatures, and a night temperature of about 6o degrees should be maintained.
Budding is an inexpensive propagative method for various deciduous plants, with only one bud being used for the scion instead of 3 or more as is usually the case of the grafted scion. Buds are taken from wood of the current season which has grown to the point at which the middle portion of the bud stick is fully developed. Buds should be cut at the time they are to be used. The best time for this method of propagation is the latter part of the summer, after the buds have matured sufficiently and the stocks have achieved active growth to facilitate peeling of the bark.
Shield budding is the most popular form of this propagative method. A shield consisting of a portion of the bark and a thin layer of wood carrying the bud is sliced from the twig. A T-shaped incision is made in the bark of the stock, bark peeled back slightly along the edges of the cut, and the shield is slipped beneath the lips of the cut bark. Gauze dipped into melted paraffin may be wrapped around the union to tape it in place. Shade is helpful in such an undertaking and it is wise to make the incision on the north side of the stock, away from the prevailing direction of the sun.
Budding—(A) The bud is cut. (B) A T-shaped cut is made in the stock, and (C) the bark loosened and peeled back slightly. (D) The bud is then inserted in the opening and (E) the union wrapped firmly.
Leave the wrapping on the juncture until the tissues have started growing together, but remove it before it constricts the stock. It is easy to identify buds which "take." They are fresh and fat. When growth starts the next spring tops of stocks should be removed with a diagonal cut so that new growth will develop soon.
Correct use of essential fertilizers
In applying fertilizer to plantings of shrubs and trees, the gardener must guard against overstimulation and untimely stimulation. His goal in fertilization is the promotion of a steady growth throughout an extended season. By fertilizing too late in the fall he makes for growth that does not mature before the onset of freezing weather; unripened wood is particularly susceptible to injuries from cold, and even matured wood may be killed by a freeze if growth is in progress. Overstimulating may produce a vigorous soft growth, more susceptible to some diseases than ordinary growth.