by Urban Forestry Operations Assistant Paul Cancik

With spring upon us, many residents are eagerly planning their gardens and starting to spruce up their yards. Pruning helps trees live longer, which allows them to grow taller and contribute to Denver’s urban canopy. With this in mind, Denver’s Office of the City Forester is offering helpful tips for pruning. It’s important to keep in mind that if you cannot safely prune your tree from the ground, it’s best to hire a licensed tree care professional since they use specialized equipment and have the necessary field knowledge. When you prune a tree, you are planning for the future, and with patience, you will ultimately have results that benefit generations to come.

Why should you prune your trees? 

• Pruning helps ensure that your tree develops a strong form/structure and prevents breakage in the future.
• Thinning your tree makes the crown (top) healthier by allowing more air and sunlight to pass through it.
• Pruning, much like watering, helps give your tree longevity; future generations will be able to enjoy it.
• Removing deadwood from your tree helps prevent insect infestation.
• If pruning is neglected, a tree can become susceptible to breakage, making the tree potentially dangerous.

What should you prune from your trees? 

• Follow the “3 D’s” of pruning: only remove Dead, Damaged and Diseased wood, especially if the tree is not established. You can also prune branches that impact the structural integrity of the tree.
• Be deliberate about what you prune from a tree.
• It’s important to prune around stop signs and to ensure sidewalks are clear to prevent accidents on or near your property. Stop signs should be clearly visible and sidewalks free of obstructions. The clearance requirements in Denver are 8’ above sidewalks and 13.5’ above streets and alleys.

When should you prune your trees?

• While you may prune your tree year-round, ideally the best time to prune is late in the dormant season or early spring, before leaves form. This is typically a good time to remove excess or undesired branches because the tree is not putting forth energy to create foliage.

• Certain trees, including American elm (Dutch elm disease) and fruit trees in the rose family (fire blight) should only be pruned while dormant to reduce the spread of disease.
• Only prune a young tree two years after it has been planted and just focus on dead, broken, crossing and interfering branches.

Tips for pruning:

• Make sure that every pruning cut you make is clean and smooth. The best tool to use for pruning is a pair of sharp bypass hand pruners for one-inch branches because they make smaller cuts that the tree can recover from faster.
• Colorado has a very short growing season compared to other regions. A shorter growing season means the tree has a shorter period of time to create and store energy, which ultimately affects how quickly a tree can recover from pruning. A young established tree can tolerate removal of 1/3 of its foliage in a growing season. A mature tree should never have more than 25% of its live foliage removed in one growing season.
• If you are pruning something off your tree that you can’t reach from the ground, it’s advised that you hire a tree care professional since they use specialized equipment such as an aerial lift truck/bucket truck and they have the needed field knowledge and expertise. In the City of Denver, tree contractors are required to be licensed and insured. A list of Denver’s licensed tree contractors can be found by visiting https://www.denvergov.org/forestry.
• If you suspect an insect problem, contact a tree care professional to develop the most effective and environmentally conscious solution.
• Covering a wound or using wound dressings is not recommended and may be detrimental to tree health.

Want to learn more? Our friends at The Park People offer a community forester program with classes that cover a variety of topics, including pruning and tree planting basics. You can sign up here:

https://theparkpeople.org/What-We-Do/Community-Forester-Program

Happy pruning!