My cottonwoods are dying!
Cottonwood trees are dying all across the Denver area. Native cottonwoods are highly resilient and thriving in many Denver neighborhoods while hybrid cottonwoods are slowly dying in some of Denver’s older neighborhoods. What’s the cause for these dying cottonwoods and what can homeowners expect for the next few years?
Why your cottonwoods are dying
Denver experienced a significant frost this year on Mother’s Day. Many trees, including cottonwoods, were already in bloom and ready for spring when bam- freezing cold and heavy, wet snow hit our Mile High city. A late freeze can cause a significant tremor to a tree’s vascular system and actually shock a tree back into hibernation. If your cottonwood hasn’t started blooming by Fourth of July, it’s most likely curtain time for your cottonwood.
Not all hope is lost though! Try watering your cottonwood around its base up to five feet away from the trunk. This may kickstart a late spring growth that will help revive your tree. Your cottonwood may also be nearing the end of its natural life. The life expectancy of hybrid cottonwoods is around thirty years. (NDSU) If you live in an older neighborhood in Denver, like in Greenwood Village or Cherry Creek, your cottonwoods may be hitting the end of their life cycle.
Canker disease in cottonwood trees
There’s also a tree disease called Canker (cytospora canker)that affects members of the poplar tree genus, including cottonwoods. It’s a fungus-based disease that affects stressed trees, which would include cottonwoods that experienced a late frost. Canker in cottonwoods can be easily identified by its sunken, discolored areas of bark. The disease causes dieback as the canker kills the bark and creates an oozing resin from the trunk. As with many diseases, the best route of action is prevention. Canker thrives on stressed and weakened trees. The best approach is eliminating lawnmower wounds, drought conditions, and improper pruning to help prevent Canker from affecting your cottonwoods.