Late winter, from mid-February until early March, is the best time to prune most urban trees. Trees are still dormant at this time of year and, unlike in early winter, wound closure will be rapid if pruning occurs just prior to the time new growth emerges.
Although some elms, silver maples, birch and walnut trees exude sap if pruned in the late winter or early spring, this should not harm the tree.
“Once a tree has established a strong root system, usually within three years after planting, proper pruning is essential to develop strong structure and desirable form,” said Keith Wood, community forestry program manager for the Colorado State Forest Service. “Appropriately pruning trees while they are young can help you avoid more expensive tree care later.”
The CSFS offers the following pruning tips:
• Know what you want to accomplish before you get out the saw – don’t remove any branches without a reason.
• Remove any torn, dead or broken branches.
• Develop or maintain a dominant leader, and don’t cut off the tops of trees.
• Prevent branches below the permanent canopy from growing upright or too large.
• Space the main branches along a dominant trunk.
• Keep all branches less than one-half the trunk diameter.
• Retain branches with wider angles to the main trunk, as compared to those with tighter angles to the main trunk.
• Limit pruning of newly planted trees to the removal of dead, damaged or crossing limbs, or those interfering with the main leader.
• Always prune at the branch collar – the point where one branch joins a larger one.
• Avoid removing more than 25 percent of a tree’s branches in any one year.
• If the job requires running a chainsaw overhead or removing large branches/entire trees, contact an insured, licensed, certified arborist. A list of these professionals for your area can be found at http://www.isa-arbor.com.
For more information about urban tree care, go to csfs.colostate.edu.