Grafting Fruit Trees (cont)
By: Nan Sterman
Finding and Storing Scion Wood
We started collecting scion wood -- new, vigorous growth trimmed from desirable trees -- in late winter for early spring grafting. Though early spring is the best time to graft deciduous fruit trees like apples and stone fruits, tropical fruit trees like avocado and citrus can be grafted later in the year. The best scion wood is no more than one year old and 1/4-to 1/2-inch in diameter. We were careful to avoid wood from diseased trees.
Most of our scion wood came from an exchange sponsored by the local chapter of California Rare Fruit Growers, but scion wood exchanges take place around the country -- even among neighbors. (Our scion wood included prunings from my parents' nectarine tree.)
If you collect your own scion wood, cut it into 12-inch lengths, and be sure to keep track of the "top" or growing end, and "bottom" or root end of the scions. Experienced grafters showed us how to mark the top with a diagonal cut and the bottom with a square cut. Then label each length with the variety name. We bundled our scions and labeled each bundle with masking tape and waterproof markers. Next, we wadded damp (not wet) paper towels around the cut ends of the scions, and placed them in large plastic bags. Finally, we sealed each bag with rubber bands and put the bags in the refrigerator. Our goal was to keep the wood moist and cool to maintain its dormancy until we were ready to graft. Scion wood can keep like this for up to six months in the refrigerator, as long as it doesn't freeze.
No matter where you live, collect scion wood from deciduous trees before the buds start to grow. Cut scions when temperatures are at or above freezing, between 10 a.m. and 2 p.m., when the sun is up and causes the sap to flow. If you live in a frost-free region of the country, you can graft at any time before new bud growth begins.
Care and Maintenance of Grafted Trees
After we grafted our trees, we waited, impatiently, for three or four weeks. Then one day, we noticed that the first graft had developed tiny green buds. Over the next few weeks, more than 30 of our 40 grafts developed buds. Within two months of grafting, all the successful grafts had started, though four or five that had appeared to take later withered. The withered grafts had sprouted using only their own energy, rather than forming a true union (called a callus) with the rootstock. Soon, however, we had substantial new growth from about two-thirds of our grafts. If you decide to try grafting, use at least 10 scions of each variety to ensure that some will take.