When you prune a tree depends to a large extent on why you choose to prune it in the first place. Light pruning and dead wood removal can be done anytime, but other work should be reserved for specific seasons. Here are some general guidelines to follow:
Winter pruning
Pruning during dormancy results in a vigorous burst of new growth in the spring, but make sure you wait until the coldest part of winter has passed. Some tree species, such as maple, walnut and birch, may “bleed” their sap during this time—it’s not harmful and will stop once the leaves fall out.
Summer pruning
To direct growth by slowing unwanted branches, pruning should be done soon after seasonal growth has occurred. Another reason to prune in the summer is for corrective purposes—defective limbs (limbs that hang down too far under the weight of the leaves) can be seen more easily.
Prune flowering trees to enhance flowering
Prune spring-blooming trees when their flowers begin to fade. Trees and shrubs that flower in mid- to late summer should be pruned in winter or early spring.
Use the 1/3 and 1/4 rules of pruning
• Never remove more than 1/4 of a tree’s crown during a season.
• Ideally, main side branches should be at least 1/3 smaller than the diameter of the trunk.
• For most deciduous (broadleaf) trees, don’t prune up from the bottom any more than 1/3 of the tree’s total height.
