Tree Pruning

"When's the best time to trim my (fill in the blank) tree? It's a question I get every weekend on GardenLine.

In most cases, especially with hardwood trees, the answer is, "December through January" ... the dead of winter, when the tree is in its highest state of dormancy.

And here's a list you should review before pulling out the pruning shears or chainsaw.

• Do not top your tree. Topping is, unfortunately, a common practice designed to encourage vigorous new growth. While that is achieved, the overall strength and structure of the tree are sacrificed. The limbs that are forced from latent buds are very often weakly attached, which makes them susceptible to wind damage. Pollarding is often confused with topping, but this practice is following by thinning, and is more technically demanding. Many Europeans utilize this practice to dwarf their trees.
• Do not remove all the lower limbs on newly planted trees. This is sometimes referred to as "limbing up." Some lower branches should be left intact for a period of time to encourage caliper growth. No more than one-third of the top growth on younger trees should be removed.
• Do not make stub cuts.
• Do not make cuts flush with the trunk or adjoining limb. The proper cut is made flush with the collar at the base of the branch. The collar is the somewhat raised area surrounding the branch union with the parent branch or trunk. This zone contains chemically-protective tissue; if it is cut off or severely cut into, proper natural 'healing' cannot occur. And, once this area is damaged, it is damaged for good. Trees have the unique ability to compartmentalize, or surround injured tissues with a protective barrier.
• Do not cut large limbs with a one-cut method. This will surely result in bark peeling from the weight of the cut limb. Rather, use the three-cut method.
• Do not use pruning paints or wound dressings. They do not encourage healing, nor do they prevent pathogens from entering the tree. Although they will not damage the tree, they will certainly prove to be an unwarranted cost. Painting could be justified where aesthetics are concerned. A dark paint can hide the glaring spots made from fresh wood being exposed from a recent cut.

• Do approach the tree, and look for any limbs that might be a hazard to someone underneath it or to a building or structure nearby. Broken branches, weak branches, narrow crotch angles, and other obvious faults should be identified. First and foremost, these limbs should be taken care of.
• Do remove any dead or dying material on the tree.
• Do remove limbs that are rubbing each other or cross over one another. Limbs that rub will develop wounds that attract insects and diseases.
• Do remove excessive vertical sprouts. Some may need to be left in place to encourage caliper growth.
• Do prune to encourage fruiting. In the case of fruit trees, thinning out of limbs will allow allocation of nutrients, etc., for fruit production. In addition, practices such as open-center pruning allow sunlight penetration for fruit ripening.
• Do choose to keep branches with wide crotch angles. Wide crotch angles are generally from 40 to 90 degrees, and are very strong as a result of being composed of solid wood. Narrow crotch angles are less than 40 degrees, and contain a bark inclusion that causes them to be very weak. Narrow crotch angles should preferably be pruned out while the tree is still young. In older, established trees, bracing and cabling may be the only resort.
• Do prune the tree to your liking. There are many different ways that one particular tree may be pruned. Even experts will have differing opinions on which branches to remove. The bottom line is: whatever you like is what you should do, so long as you utilize proper cutting techniques and pruning methods.