Fruit and crabapple trees: Pruning can typically be done from January through the end of March as long as the trees remain dormant. You don’t want to do major pruning when the temperature is above 50 degrees if at all possible, and there might be some desiccation that could occur if it is below zero when you are pruning. I am concerned this year about potential winter damage on the less-hardy fruit trees (peaches, apricots and sweet cherries) with the wild temperature fluctuations and the prolonged bitter cold.
When pruning fruit trees (and other woody plants), be careful not to remove more than approximately 25 percent of the old growth. Keep in mind that the spurs that bear the flowers and fruit are already on the tree and pruning removes them. Prune for good light penetration and structural strength to support the weight of the fruit. Sixty-degree crotch angles between the branch and trunk are the strongest and most fruitful in terms of fruit production.
In pruning for strength, remember that V-shaped crotch angles are not as strong and don’t produce as much fruit. Remove crossing and rubbing branches, dead branches, diseased branches, suckers that come up around the base of the tree and water sprouts (the vertical fast-growing twigs that usually appear in the middle of the branches).
For more detailed information on pruning apple trees, see UWEX publication A1959 “Training and Pruning Apple Trees”at http://learningstore.uwex.edu/.