Why we need to eliminate the Tree of Heaven

By Bonnie Orr
WSU Chelan/Douglas County Master Gardener

tree of heaven flower.
A single, full-blooming Tree of Heaven can produce up to 350,000 seeds, so it’s best to eliminate it before it reaches that stage. – Wikimedia/Luis Fernandez Garcia
Tree of heaven
Controlling the spread of Tree of Heaven, Ailanthus altissima, is the most effective means of preventing the spread of the spotted lantern fly, an invasive pest that causes damage to fruit trees and ornamental trees. – Wikimedia/Göterrbaum
Bonnie Orr
Bonnie Orr – WSU Extension Chelan/Douglas County Master Gardener – photo by Don Seabrook, Wenatchee World

The United States has had all types of migrants since the first European settlements. Dandelions and angle worms were introduced, as well as many invasive and noxious weeds and insect pests.

In the 21st century, the world is truly a global economy, so our migrants have changed to insect pests hidden in shipments of goods from other parts of the world for which we have not yet developed sure means of controlling them.

In the last 20 years, gardeners in North Central Washington have seen the eruption of the spotted wing drosophila, a fruit fly that damages ripening fruit, and the brown marmorated stinkbug that eats nearly anything organic and has become a scourge on the East Coast, and the Asian hornet or northern giant hornet.

Now there is a new pest that we hope we can control in the West before its population explodes. The new pest, the spotted lanternfly, Lycorma delicatula, is actually spread by using another inadvertent plant pest, the Tree of Heaven, as a host.

The Washington Invasive Species Council wants to have these unwanted and unloved trees eliminated from the landscape because that is the most effective means of preventing the spread of the spotted lantern fly, which like the tree comes from China.

The spotted lanternfly uses the Tree of Heaven as a host. The lanternfly sucks the sap from stems and new growth of ornamental trees such as maple, oak, pine and willow and fruit trees, including apples and grapes. It lays its eggs on the smooth bark of the Tree of Heaven. It is a remarkable-looking insect that is brightly colored, but we do not want to see it in Chelan and Douglas counties.

Did you ever read the book or see the classic movie, “A Tree Grows in Brooklyn?” The tree featured in the book is Ailanthus altissima, a tree brought to the U.S. from China for its “beauty.” Nothing was known about how aggressively this plant spreads.

The tree is casually known as a “trash tree.” People seldom plant it in their yards. It grows in uncultivated places, in disturbed land, near abandoned buildings, and in cracks in sidewalks. One tree in a neighborhood can produce enough seeds and suckers to populate several square blocks.

So, what is a short-term management of this pest? Before the trees bloom and send off up to 350,000 seeds per tree, cut down the trees that live on the north and east side of your property since trees in other areas of your yard provide your shade. It is best to kill the tree with herbicide before you cut the tree down or the tree will send up lots and lots of suckers up to 50 feet from the tree.

If you cannot cut them down or arrange to have them cut down, kill them with herbicide. There are a number of techniques. You can spray the leaves or the basal bark. You can hack the stems and squirt herbicide in the cut. July is the time to treat the tree with systemic herbicide.

Generally, it takes two years to totally eliminate the tree. After you have killed the tree and have selected not to cut it down, there are several options. First, it can become a snag tree for cavity nesting birds. Or if it not too close to your house, you can plant rapidly growing vining plants to climb up the dead branches. Wisteria, native clematis and climbing roses, will bloom colorfully. Even ivy, kept in control, can create a sense of green on the dead branches of the Ailanthus.

If you would like assistance with managing your Tree of Heaven, contact the Chelan County Noxious Weed Control Board or The Douglas County Weed Management Task Force. These organizations can offer site-specific recommendations for a tailored management plan that best fits the location and extent of the problem. Email the WSU Chelan-Douglas Master Gardeners (chelanmastergardeners@gmail.com) for additional information and lists of herbicides to control this pest tree.

A WSU Chelan and Douglas County Master Gardener column appears weekly in The Wenatchee World. To learn more, visit bit.ly/MGchelandouglas or call (509) 667-6540.