Fruit tree pruning is an annual cold-weather activity for those who want their flowering trees to supply delicious and nutritious homegrown fruit. The best timing for this do-it-yourself plant surgery can vary from year to year. However, it follows fairly specific guidelines.

Pruning shouldn't start until the trees have been fully dormant for several weeks. In Kansas, that often means some time in January. But, pruning when temperatures are below 20 degrees isn't a good idea, either. That can lead to tree injury. The ideal period for pruning can sometimes extend through March. Because of our unpredictable weather, however, many fruit growers prefer getting the job done as early as they can.

The pruning process must be completed by early spring – before the trees' buds swell, yet when temperatures won't drop below 40 F for 24 hours. Meeting this deadline gives gardeners time to apply a dormant oil treatment to kill such pests as scale insects, mites, pear psylla and pear leaf blister mites.

Start with the oldest trees first. Older, larger wood tolerates lower temperatures much better than young wood. But, pruning before full dormancy leaves fruit trees vulnerable to winter's sub-zero temperatures. In contrast, pruning in mid to late winter reduces the likelihood of bark tearing down the side. In addition, the pruning wounds quickly heal once spring growth begins.

Neglected fruit trees are more prone to damage caused by wind, ice, branch rubbing and awkward growth. To help them develop a strong tree structure, pruning should begin, if needed, when the trees are planted and continue every year after that.

Even so, some injury will occur each year, due to weather extremes, diseases, insects and the weight of fruit. Removing this damaged wood is important to tree health. Pruning in winter allows gardeners to identify undesirable or damaged branches without the cover of leaves.

Opening up the canopy of a tree for sunlight penetration is yet another reason to prune. The sun must penetrate a tree's leafy canopy for its buds to be able to develop mature fruit. Additionally, most fruit trees require pruning to keep their size within workable bounds – in both branch spread and tree height.

Neglected apple trees produce so many branches that little energy is left for fruit production. Overgrown apple trees are also difficult to harvest and spray. Gardeners who inherit such a tree are often at a loss as to how to get it back in shape. Often the best recommendation is to give up on the old tree and start over with a new tree. However, trees may have sentimental value that will make revitalization worth the time and effort. Keep in mind that this will be an ongoing process because no more than 30 percent of the tree should be removed in one year.

First, remove all dead wood. This does not count toward the 30 percent. Next, remove suckers from the base of the tree. Then, choose approximately six of the best branches to keep as scaffold branches. Remove all others. Candidates for removal include branches with narrow crotch angles, which are more likely to break in wind and ice storms, and those that cross branches you will save. This may be all that is possible the first year if the 30 percent threshold has been reached.

Thin the branches on each scaffold branch. Remove crowded branches to open up the tree to light and allow humidity to escape. Shorten each scaffold branch by cutting back to a side branch. When you are through, the tree should have enough wood removed so that a softball can be thrown through the tree. Later, the tree will produce vigorous side shoots from the trunk and vertical shoots from the scaffold branches called water sprouts. These water sprouts produce few fruit and should be removed throughout the growing season so the center of the tree stays open.

Additional information on how to prune fruit trees is available on the Web at http://www.oznet.ksu.edu/library/hort2/c631.pdf .