Chip budding is a technique
that may be used whenever mature buds are available. Because the bark does
not have to "slip," the chip-budding season is longer
than the T-budding season. Species whose bark does not slip easily without
tearing - such as some maples - may be propagated more successfully by chip
budding than by T-budding.
Preparing the Stock and the Scion Bud.
Although all the basics in handling budwood and stock are the same for Chip Budding and T Budding, the cuts made in chip budding differ radically. The first cut on both stock and scion is made at a 45o to 60o downward angle to a depth of about 1/8 inch (Figure 15). After making this cut on a smooth part of the rootstock, start the second cut about 3/4 inch higher and draw the knife down to meet the first cut. (The exact spacing between the cuts varies with species and the size of the buds.) Then remove the chip.
Figure 15. Rootstock cut for T budding.
Securing the Bud.
Cuts on both the scion (to remove the bud) and the rootstock (to insert the bud) should be exactly the same (Figure 16). Although the exact location is not essential, the bud is usually positioned one-third of the way down from the beginning of the cut. If the bud shield is significantly narrower than the rootstock cut, line up one side exactly.
Figure 16. Removing chip from budstick.
Wrapping is extremely important in chip budding. If all exposed edges of the cut are not covered, the bud will dry out before it can take. Chip budding has become more popular over the past 5 years because of the availability of thin (2-mil) polyethylene tape as a wrapping material. This tape is wrapped to overlap all of the injury, including the bud (Figure 17), and forms a miniature plastic greenhouse over the healing graft.
Figure 17. Chip bud wrapped with plastic tape.
When irrigation is available, apply water at normal rates for plants that bud before August 1. Ornamental peaches and pears often will break bud and grow the same year they are budded. Dogwoods and most other species budded after August 1 should be irrigated at a normal rate for only two to three weeks after budding except during extreme drought. Following these irrigation practices will enable buds to heal completely with no bud break before frost.
Although budding rubbers and polyethylene tape reportedly decompose and need not be removed, studies show that unless they are taken off, binding or girdling of fast growing plants like Bradford pear may occur within a month. Summer buds should take in two to three weeks.
On species budded in early summer, it may be desirable for the buds to break and grow during the same season. In this case, either remove the stock tops entirely or break them over within a few weeks of budding to encourage the scion buds to break. Once the buds have broken, completely remove the stock above the bud or keep a few leaves intact but remove the terminals, depending upon the species.
For dogwoods and other plants budded in late summer, remove the tops just before growth starts the following spring. A slanting cut away from the bud is preferred (Figure 18). If possible, set up stakes or other devices to insure that straight growth will occur before the buds break. Straight shoots, however, are so essential to the growth of high-quality grafted and budded stock that stakes should be set as they are needed.
To insure a top-quality plant, it is essential to remove unwanted sprouts. These sprouts should be rubbed off as soon as they are visible so that they do not reduce the growth and quality of the budded stock. If they are removed regularly and early, large scars or "doglegs" can be avoided.
Figure 18. Budded plant after pruning.
Collecting Budwood for Shield Budding
I am collecting budwood for shield budding, keep these points in mind:
- The best budwood is from the second flush of growth from the end of a branch.
- Budwood should be rounded with plump buds. Leaves should be trimmed to very small stubs as the budwood is cut from the tree.