Tree-of-Heaven Isn’t “Heavenly”

Tree-of-heaven header image

If you start looking around Clackamas County, it won’t take you long to find the invasive tree-of-heaven (Ailanthus altissima). This state-listed noxious weed is increasingly common in many of our urban areas where it flourishes.

Tree-of-heaven seems right at home in alleys, roadsides, railways, vacant lots, even cracks in the sidewalk. Very large trees can be found growing in many yards and vacant lots. Often, these trees were intentionally planted as ornamental. These trees can reach heights up to 80 feet in height. They can also spread seed for blocks around.

Recently, tree-of-heaven has been featured in the news. This news account documents the trials of one local resident as he struggles to deal with a tree on his property line. This particular tree is slowly destroying his home’s foundation. In response to this news story, Clackamas SWCD WeedWise staff have been busy. They have received a large number of calls, emails, and hotline reports from concerned citizens.
Tree of heaven flower (Photo:

Tree of heaven flower (Photo:

Tree-of-Heaven is Real Threat to Property Owners

The threat from tree-of-heaven is real! If this tree is growing on your property, you should take action now.

  • Due to its rapid growth and structural weakness, tree-of-heaven is considered a fall hazard. Its roots damage pavement, roads, and building foundations.
  • Tree-of-heaven produces allelopathic chemicals in its leaves, roots, and bark. These chemicals discourage the germination, growth, survival, and reproduction of other plants.
  • These trees can form dense thickets which reduce wildlife habitat, particularly in riparian areas.
  • It is a favorite host for the spotted lanternfly, an invasive and agriculturally damaging pest. (NOTE: If you find a spotted lanternfly on your property, please report it immediately).
  • Tree-of-heaven can also be toxic. See caution information below.

Caution: Tree-of-heaven has been known to cause skin irritations or allergies in some people. Additionally, there have been rare reports of myocarditis (inflammation of the heart muscle) from exposure to sap through broken skin. People who work around the tree should wear personal protective equipment, including eyewear and gloves.

Best Management Practices

Remove small seedlings and saplings. To help, the Clackamas SWCD WeedWise program has weed wrenches and other tools available through our equipment library. These tools can be borrowed at no cost to help you safely remove these small trees. Contact us to reserve a weed wrench today.

Larger trees are much more difficult to manage. These large trees have extensive root systems that can spread up to 50 feet in all directions. Cutting large trees causes these roots to sucker, potentially leading to even more damage.

An Integrated Pest Management (IPM) approach is needed to effectively manage tree-of-heaven. An IPM approach uses several different management strategies to be effective. These strategies include chemical controls, one of the only controls found to be effective in dealing with tree-of-heaven. To assist Clackamas County residents through this process our WeedWise team created a Tree-of-heaven Best Management Practices (BMP). This document will help guide you through the management process.

TREE-OF-HEAVEN Best Management Practices

Take action now! It isn’t too late to protect your home from tree-of-heaven.

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Clackamas SWCD