Top grafting old apple trees in the Tukey Orchard

During the past five months, I have been the teaching assistant for Plant Propagation (HORT 251) here at WSU. I prep labs, write, administer, and grade quizzes, grade lab reports, and entertain the students. On a wonderfully sunny day this week, we took the class out to the Tukey Orchard.

The R.B. Tukey Horticulture Orchard is just off campus and was established for research and education purposes. Surplus fruit is sold to the public and there are u-pick cherries, apples, pears, and peaches (in mild years). Many of the trees are over 30 years old. Aging trees begin to slow in productivity and decrease in yield. The orchard houses lots of varieties. Many varieties were experimental and never gained momentum while other varieties have simply fallen out of favor over the decades. The solution to an aging unfashionable orchard: top-grafting!

Top-grafting is a grafting technique used to revitalize old established orchards or replacing a variety that may be waning in popularity with a rising star (such as 'Pink Lady' or 'Honeycrisp).

In the spring, the established tree's branches are cut back close to where they arise from the trunk. It is important to top graft in the spring, as the bark 'slips' away from the inner wood due to cambium growth. The scion wood's cambium must come into contact and heal with the rootstock's cambium. Slipping the bark away from the cambium, allows you to securely place the scion cambium in contact with the rootstock cambium.

Scion on left has been slipped between bark and cambium. Scion on right has been sealed with grafters wax to prevent it from drying out.

The scion material are new shoots that are about the thickness of a pencil. The lower ends must be cut in a wedge shape to maximize exposure of the cambium and to slip securely in between the bark and inner wood of the rootstock. Cutting the scion in the perfect wedge is a lot more difficult than it initially appears and requires confidence around very sharp knives.

A vertical cut is made about 3/4" down the bark of the rootstock, the bark is gently pried away from the cambium, and the scion is pushed down in between the bark in inner part of the rootstock.

Scion is nailed in place to secure.

The base of the scion is then covered with grafters wax to prevent drying out. The scion is pruned back to 3-4 buds to promote graft healing rather than vegetative growth. All wound surfaces are painted with seal and heal to prevent water loss and disease infection. About 3-4 scions are grafted into each main branch of the rootstock.

Did I mention that I am TAing a great group of students? Well, they're great.

And they did a mighty fine job on this old fruit tree too!