Grafting

Grafting is the process of connecting two different plants so they grow as one. The advantages of grafting include combining attributes that don't naturally occur in a single plant, for instance flavorful fruit with dwarfing or disease-resistant roots. All grafts are composed of two parts: the detached part of one plant, called the scion, which becomes the flowering and fruiting top part of the plant; and the rooted and growing part of another plant, called the rootstock.

Over the years many grafting techniques have evolved, but the whip-and-tongue graft is favored by most professionals who propagate fruit trees. It works best when both scion and rootstock are small (1/4 to 1/2 inch in diameter) and the same size. In part because of the added surface provided by the tongue, this graft heals fast and forms a particularly strong union. Much experienced in the technique is Nick Botner, a hobby orchardist in western Oregon, who guided this article.

The whip-and-tongue grafting process begins in early winter once plants have become fully dormant and growth hormones are concentrated in next season's buds. The only tools you need now are bypass pruning shears to collect the scions and a plastic bag in which to store them. Although you won't be grafting for several months, choose scions of the same diameter as that of your well-established rootstock (which should have been planted one year earlier). Select scions that are about pencil thickness, 6 to 8 inches long, with three or four buds. Label them by origin and with the variety name, and be sure to indicate the top and bottom. Refrigerate the scions in plastic bags until early spring.

The ideal time to graft is between January and March, just prior to the natural burst of spring growth. To make clean cuts, you'll need a sharp, sterile knife with a flat (not beveled) blade. (See Steps to A Successful Graft, below.)

Within a month after grafting, expect new growth from both rootstock and scion. The rootstock will send out suckers during the first year. Remove them down to the very base of the tree to redirect the energy from the tree's roots into the scion. On the other hand, leave new scion growth untouched until the longest is 6 to 8 inches, normally toward the end of May. At this point, select the best shoot to form the main trunk of the new tree. Pinch out the growing tips of the other shoots, leaving five or six leaves on each shoot to aid the formation of a strong union. (In fall, cut away these pinched shoots.) Also in May, remove the binding by running a sharp knife up the back of the rootstock, taking care not to injure the bark. Water your grafted tree weekly throughout the first year.

Steps to A Successful Graft

  1. In early spring, match scion wood to rootstock (the scion must be fully dormant). Ideally, they should be exactly the same diameter, though the rootstock may be slightly larger.
  2. Make a slanting cut halfway between buds on both scion and rootstock, holding them together to ensure that the angle is the same. Make clean cuts using a very sharp knife.
  3. Make matching slits (the tongues) about 1/4-inch deep in the surface of each cut. These notches interlock when the scion and stock are joined.
  4. Join the scion and rootstock by aligning their cambium layers. (The cambium is the active, green layer of tissue between the bark and the wood.)
  5. Make the graft by gently pushing the scion into the rootstock and interlocking the tongues. If the scion and rootstock widths are slightly dissimilar, match the cambium layers on at least one side of the graft.
  6. Wrap and stake the graft to secure it until the bond is strong. Use a cut rubber band, winding from the bottom up, and slipping the end under the final loop. Tying the graft to a 1-inch stake will provide support when top-heavy scion growth forms. (Adequate trimming may preclude the need for staking.)
  7. Seal the union by covering the grafted area with a thin coat of water-based grafting sealant.
  8. Three years later, the graft is strong enough to support the growing scion and any fruit it bears.

Kris Wetherbee, a market farmer and writer, lives in Oakland, Oregon. She also wrote for National Gardening Meet the Asian Pears and Corn of Many Colors.

Article published on June 23, 2008.

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