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.
“Applying proper pruning techniques at the correct time of year is an essential component of maintaining our urban forests,” said Keith Wood, community forestry program manager for the Colorado State Forest Service. “By being proactive and pruning trees during the late winter, residents can help maintain the health, appearance and safety of their trees for the long-term.”
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.
• Develop or maintain a dominant leader, and don’t cut off the tops of trees.
• Remove any torn, dead or broken branches.
• 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.
• Always prune at the branch collar – the point where one branch joins a larger one.
• Limit pruning of newly planted trees to the removal of dead, damaged or crossing limbs, or those interfering with the main leader.
• Avoid removing more than 25 percent of a tree’s branches in any one year.
• Emerald ash borer, an invasive insect responsible for the death or decline of tens of millions of ash trees in more than 20 states, has now been detected in Colorado. Urban foresters now recommend close inspection of ash trees, especially during any pruning activities. For more information visit http://www.eabcolorado.com.
• 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 http://csfs.colostate.edu/.