If you want more apples, you have to learn how to prune

If I hadn't needed more sunlight and some additional lumber for the cottage we are building here in Maine, I might never have learned firsthand how the fruiting potential of old apple trees can be restored.

It happened this way: Two winters ago I felled several large trees near the building site so winter sunlight would not be blocked from the home when it was built. The trees themselves would be used for roofing timbers. However, a quite unexpected result of that exercise on snowshoes was a more-than-two-bushel harvest of great-tasting pie apples this past fall.

At the time the trees came down, I barely noticed a gnarled, partly rotting runt of a tree that was almost crushed by the toppling giants. But, once freed of the imprisoning shade, it responded with vigor, sending several sturdy branches skyward the following summer.

This past year those new branches were loaded with medium-size green apples that turned yellow in the fall. They were incredibly tart. One bite might pucker your mouth for a month, but, oh, what delicious pies and cobblers came from those apples!

Obviously, the tree is worth keeping, so my concern is to ensure its continued productivity.

The records suggest that the undulating hillsides that form the woodlot I now own were farm fields back around the turn of the century. Sometime before World War I, the fields were abandoned and the forest returned to engulf the lone apple tree that now stands in front of our cottage. In other words, the tree has to be close to 75 years old, which is far past its productive prime.

Apple trees stop producing with age, largely because their tops outgrow the ability of the root system to feed the numerous branches. Pruning corrects the imbalance between root system and top and so enables the tree to keep on fruiting. Moderate fertilizing and good sunlight are two other basic needs of good fruit production.

The tree on my lot had died back considerably because of the heavy shade. It had been naturally pruned, in other words, and was ready to go the moment it was given sun. The sudden elimination of competition from other tree roots had much the same effect as giving it a shot of fertilizer. (The decaying roots of the felled trees would also release stored nutrients into the soil.)

Meanwhile, the unintentional rejuvenation of the apple tree led me to look into ways in which old apples, left unattended for many years, may be restored. Apparently, the slow advance of suburbia into abandoned orchards has prompted many knowledgeable gardeners to do the same thing. Generally, it is a two-year process:

First year: Preferably in the early spring before growth starts, remove approximately two-thirds of all the suckers or water sprouts that have sprung up around the base of the tree. Also remove all dead wood or damaged branches and any branch that rubs against another.

Cut one to two feet off the end of all lateral branches to reduce the overall size of the tree.

When pruning is done in late winter or early spring, the wounds quickly heal during vigorous early-season growth. By not removing all the water sprouts at one time, you spare the tree some of the shock that accompanies drastic pruning.

Apply a good mulch out to the drip line of the tree to smother grass, weeds, or other competitive growth. A light feeding should be given at this time.

Second year: Remove the remaining suckers and begin thinning out the branches. In particular, remove any branch that grows the ''wrong way'' - from the outside back through the center of the tree. The idea is to encourage good lateral growth, rather than vertical branches.

One way to do this is to remove a vertical branch just above the point where a promising lateral branch begins. The vigor of that particular branch will then be channeled into the lateral growth.

Remove all new water sprouts as they appear, whatever the time of year. From the second year on, light midsummer prunings will do much to maintain the tree at the desired size and encourage the development of stubby fruiting spurs.

Recent research has shown that the feeder roots of apple trees are concentrated in from the drip line and a lot closer to the trunk of the tree than was at one time thought. With large old trees, these feeder roots begin about four feet out from the trunk of the tree and extend out another three feet. Apply any applications of manure or fertilizer in this area.