Chapter 20

Vegetative Plant Propagation

Plant Propagation by Grafting

Grafting is the act of joining two plants (or their parts) together. The portion of the graft that is to be propagated is called the scion. It consists of a piece of shoot with dormant buds that will produce a stem and branches. The rootstock, or stock, provides the new plant’s root system and sometimes the lower part of the stem. To make a successful graft, the cambium of the scion must line up as closely as possible with the cambium of the rootstock and make good, sustained contact. The cambium is a layer of cells located between a stem’s xylem and phloem. New xylem and phloem cells originate from cambial tissue. This union must be kept from drying out until the graft “takes.” One general rule of grafting is to always note which is top and bottom of a scion stick; a scion will not grow if it is inserted upside down. The best time for grafting is in the spring just as growth starts. Grafting techniques can be divided into four basic types, usually referred to as cleft, bark, whip-and-tongue, and side grafting. The method selected is largely determined by the size of the stock and scion.

Cleft Grafting

Cleft grafting (See Figure 20.9) is used for top-working and should be completed before active growth of the stock. It can be used on either young or mature trees. It is used to change over (rework) an established fruit (scion) variety to a new (more desirable) variety, or to obtain multiple varieties on a single tree, or to insert a pollinizer branch for self-incompatible trees like apple. The scion for the cleft graft should be made from year-old wood about ¼-inch in diameter 3 to 5 inches (8 to 13 cm) long. It is desirable for a scion to contain three buds and to be long enough that it can be inserted with the lowest bud just above the stock. Always note which is top and bottom of a scion stick; a scion will not grow if it is inserted upside down. Saw off the stock at a right angle in relation to its main axis of the branch. Make the cut so there are 4 to 6 inches below with no knots or side branches.

Bark Grafting

Unlike most grafting methods, bark grafting can be used on large limbs from an inch to several inches in diameter (See Figure 20.10). Collect scion wood 3⁄8 to ½ inch in diameter and 4 to 5 inches (10 to 13 cm) long with two to three buds when the plant is dormant. Wrap the wood in moist paper, place it in a plastic bag and store it in a refrigerator. Saw off a limb or the trunk of the rootstock at a right angle to itself. The bark graft can be made only when the bark slips or easily separates from the wood.

Whip-and-Tongue Grafting

Whip-and-tongue grafting is one of the most common and useful grafts for woody plants (See Figure 20.11). It is used for top-working and producing new plants, primarily deciduous trees. Both the rootstock and scion should be of equal size and, preferably between ¼ inch and ½ inch in diameter. The scion and rootstock usually are the same diameter, but the scion may be narrower than the stock. The scion should be year-old wood, preferably the same diameter as the stock. If the stock is larger than the scion, contact can be made on only one side. The scion should never be larger than the stock. Close alignment of the cambial tissues in the stock and scion are critical for grafting success. The technique is similar to splice grafting except that the whip on the rootstock holds the tongue of the scion in place (and vice versa).

Side Grafting

The side graft is suitable for plants that are too large for a whip graft but not large enough for easily making a cleft or bark graft (20.12). The plant or branch that will serve as the stock should be 1 to 2 inches (2.5 to 5 cm) in diameter. The material for the scion should be about ¼ inch in diameter. To prepare the stock select a smooth area near the base. Use a sharp knife to make a slanting cut into the stock. The cut should angle downward and extend about halfway through the branch. The scion should contain two to three buds and be about 3 inches long. Make a wedge at the end of the scion similar to that made for cleft grafting, but make it shorter. It is not necessary to make the cuts more than an inch long.

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