LEE REICH / AP
A grafted chestnut tree in New Paltz, N.Y. Chopping and grafting may look brutal but can result in beautiful fruit trees.
Visitors to my garden this time of year are often astonished to see me lopping the tops off some of my trees.
No, I'm not the Henry VIII of horticulture, chopping the head off any tree that no longer meets my fancy. OK, I am actually lopping the head off any tree that doesn't meet my fancy.
I part ways with Ol' Henry, though, because first, lopping the head off a tree does not kill it, and second, I graft on a new head. A few years after this seemingly brutal operation, the tree looks as chipper as ever. And it has a head that I like better – or else off it comes again. I do this type of grafting, called topworking, mostly on my apple trees, but it could be applied to many other kinds of fruit or ornamental trees.
For instance, if you don't like the growth habit of your red maple or the leaf shape of your Japanese maple, you can just lop back the head and change it. Same goes for the flower color of a crab apple or flowering cherry. Each time I lop back one of my apple trees, I can make that tree into any one of the more than 5,000 other varieties of apple. Mostly, you can only graft the same kinds of plants together – any variety of apple on an apple trunk, cherry on cherry, maple on maple, etc.
GATHER YOUR STEMS
Before you can topwork any tree, you have to have stems, called scions, of the variety to which you want to change the plant. You might get scions from a neighbor's or friend's tree that you have admired. I often get scions for grafting mailed to me from enthusiasts elsewhere across our fruited plain, or from government institutions. Healthy portions of last year's growth, each cut into pieces a foot or so long, are ideal to become scions. They can be collected anytime in winter or early spring, as long as stems are showing no signs of growth and temperatures are above freezing. Once you have scions in hand, put them in the refrigerator. Wrap them well in plastic, perhaps with a damp cloth to keep them plump with moisture.
A FEW CUTS AND YOU'RE FINISHED
The ideal time for topworking is when buds on the trunk are just beginning to grow; the scions are still under refrigeration in their winter sleep. This way, the scion will have time to knit to the lopped-back trunk and hook up its plumbing before its buds expand into thirsty new shoots.
The actual grafting operation is simple, and there are a few ways to go about it. The method I'll describe is the cleft graft, practiced by gardeners for thousands of years and best done on trunks 1 to 4 inches across. Wedge grafting and bark grafting are among other methods of topworking, described in such books as "The Grafter's Handbook" by R. J. Garner (Sterling Publishing, 1993) and "Plant Propagation: Principles and Practices" by H. Hartmann, D. Kester, F. Davies and R. Geneve (Prentice-Hall, 2010), and are useful with trunks even a foot across.
After lopping off the tree's head and squaring off the top of the trunk with a clean saw cut, begin the cleft graft by hammering the blade of a heavy knife right down into the stub to form a 2- or 3-inch split. Remove the blade and let the split close up.
Next, cut two scions to fit into the split in the trunk. Do this by slicing wood from the bottom 2 to 3 inches on either side of each scion, making that bottom portion wedge-shaped in cross section, but slightly asymmetrical. (You "plant" more than one scion into the trunk when topworking as insurance against failure; a couple of years later you prune to leave only the one that made the best growth.) Now, force a screwdriver into the middle of the slit in the trunk to open it up, and slide each scion into each of the outer edges of waiting gap. The better the alignment of the line between the bark and wood on each scion with this same line on the trunk, the better the healing, because the layer just beneath the bark is the source of all new cells at the graft.
Once scions are snuggled in place and aligned, remove the screwdriver to let the split close up and firmly hug the two scions.
DRYING IS YOUR ENEMY
If your timing is right, and trunk and scions are in good contact, the only remaining threat to success is from the cut ends drying out. Avoid this by thoroughly coating all cut surfaces, including the tips of the scions, with some sort of pruning paint or grafting wax. My favorite is a gooey black stuff called "Treekote."
Check the graft a day after the operation to make sure all surfaces are still thoroughly sealed. Then stand back, because with an established root system it's possible to get 3 feet or more of growth from a scion in one season!