How to Graft an Apple Tree
What Is Grafting?
Grafting describes any of a number of techniques in which a section of a stem with leaf buds is inserted into the stock of a tree. The upper part of the graft (the scion) becomes the top of the plant, the lower portion (the understock) becomes the root system or part of the trunk. Although grafting usually refers to joining only two plants, it may be a combination of several. A third plant added between two others becomes the trunk or a portion of it. This is called an interstem.
Some cultivars (varieties) of plants do not come true from seeds. The seed from a Haralson apple will produce an apple tree, but it will not produce a Haralson apple tree. In other words, fruit trees cannot be reproduced "true" to the original cultivar from seed. They can only be reproduced by grafting. Grafting (top working), is a way to change a large tree from old to a new variety. It is also a method of using a root system better adapted to soil or climate than that produced naturally by an ungrafted plant. By using special understocks or interstems, grafting is a way to produce dwarf plants.
What can be Grafted?
Most varieties of a particular fruit species are interchangeable and can be grafted. Because of differences in vigor, some are better able to support others as understocks. Plants of the same genus and species can usually be grafted even though they are a different variety. Plants with the same genus but of a different species may often be grafted. But the result may be weak, short-lived, or they may not unite at all. Plants of different genera are less successfully grafted although there are some cases where this is possible. Plants of different families cannot be grafted successfully.
What Trees Can Be Grafted?
Young, vigorous fruit trees up to 5 years old are best for top working. Older apple and pear trees of almost any age can be top worked but the operation is more severe and those over 10 years old must be worked at a higher point. Young trees should have 1 to 2 feet of branch between the trunk and the graft. Otherwise the good crotch formation of the understock will be lost by the trunk expanding past the union. Trees up to 5 years old can be grafted at one time. On older trees about half--the upper and center part only--should be worked at one time. The remainder should be worked a year later.
How to Collect and Store Scions
Scion wood may be collected during the winter. It should have a diameter of 1/4 to 3/8 inch. If the scions are left on the tree until spring, there is some danger that the buds will start to grow or be injured during winter. Store in a cold, moist place at temperatures close to 34 degrees F. At home, a few scions could be stored in a plastic bag in the refrigerator with moist paper towels. Do not store in a freezer.
When to Graft
It is best to graft in the spring, from the time the buds of understock trees are beginning to open, until blossom time. The usual time is April or early May.
What is budding?
Budding is a method of grafting in which the scion (upper portion of the graft) is a single bud rather than a piece of stem or twig. It is the most commonly used method for fruit tree production in the nursery, but can also be used for top working plum, cherry, apricots, and peach as well as young apple and pear trees. (Cherry, plum, and apricot are not easily cleft grafted or whip grafted.)
Why propagate by budding?
Budding, particularly "T" budding, is faster than any other grafting technique. Even for the beginner, the percentage of successful unions is usually greater than with other forms of grafting. Budding is also well adapted to plant shoots from 1/4 to 1 inch in diameter. In larger branches, buds may be inserted in vigorously growing twigs near the upper part of the plant. Besides ease and success, a stronger union is formed than those made with other grafting techniques. Because only a single bud is inserted, you can produce a number of new plants even when scion wood of a new variety is scarce.
When is the time to bud?
"T" budding can be done almost any time that the bark of the stock slips (easily separates from the wood) and buds are fully developed. Most budding is done from July 15 to August 15. Buds set at this time normally remain dormant until the following spring. In cold climates, bud growth in fall is undesirable because young shoots are subject to winter injury. Spring budding (in May) is possible, but is less desirable than fall budding.
What Tools and Materials are Needed?
Knife. A good quality knife, able to hold a sharp edge, is the key to good grafting. Although special grafting and budding knives are desirable, you can use almost any good pocket knife. Keep material to sharpen the knife handy.
Grafting tape. This is a special tape with a cloth backing that decomposes before girdling can occur. Tapes may be used for binding grafts where there is not enough natural pressure. Rubber Electrician's tape is an excellent material that will bind and protect graft unions.
Plastic electrical and masking tapes are also used. Plastic tape can be a problem because it lasts to long and may constrict the growth of the graft. If used, choose a brand that is elastic and will stick well to itself. Do not stretch this tape too tightly or it may crack or weather. Masking tape is suitable where little pressure is required, as in the whip graft.
Asphalt water emulsion. Is widely used as a protective coating on graft unions. It is of pasty consistency and can be applied with a brush. It is preferable, however, to smear it on thicker with a small paddle.
Budding strips. Budding strips are elastic bands. They look like a wide rubber band that has been cut open.
Grafting tool. Specially designed tools have been developed for grafting. The most common one is used for cleft grafting. It has a blade used to split the stub and a wedge to hold the split open while the scions are inserted If this tool is unavailable, use a heavy knife and a fairly wide wedge at least 2 inches long for cleft grafting. Use a mallet or hammer to pound the grafting tool or heavy knife into the stub. Split the stub and insert the wedge to open the split.
Reasons for Graft Failure
1. Stock and scion were not compatible.
2. The cambiums were not meeting properly.
3. Scions were upside down.
4. Grafting was done at the wrong time.
5. Understock or scion were not healthy.
6. Scions were dried out or injured by cold.
7. Scions were not dormant.
8. The graft was not properly covered.
9. The scion was displaced by storm, birds, or other means.
10. The graft was shaded too much by other growth.
11. The graft was attacked by insects or disease.
12. The graft union was girdled because tape was not cut or released in time.