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News / Life / Clark County Life

Tree-of-heaven is an otherworldly invader in Northwest

Contrary to its name, fast-growing species is a menace that’s difficult to eradicate

By Lauren Ellenbecker, Columbian staff writer
Published: April 23, 2023, 6:00am
8 Photos
Tree-of-heaven, otherwise known as ailanthus altissima, is a fast-growing shade tree that wreaks havoc on both local ecosystems and homeowners. The tree, native to China, excels at extending its network of roots, which have been known to grow through walls and concrete, as well as outcompete other plants.
Tree-of-heaven, otherwise known as ailanthus altissima, is a fast-growing shade tree that wreaks havoc on both local ecosystems and homeowners. The tree, native to China, excels at extending its network of roots, which have been known to grow through walls and concrete, as well as outcompete other plants. (lauren ellenbecker/The Columbian) Photo Gallery

Who knew something so sweet-sounding could be incredibly menacing.

Tree-of-heaven is obnoxiously noxious, earning it a designation on Washington’s quarantine list, which prohibits its sale or distribution within the state.

However, the deciduous giant is unassuming, which is why Vancouver urban forestry officials host tree-of-heaven awareness walks, one of which fell on Saturday morning ahead of an Earth Day festival.

So, what’s the tree’s damage?

Tree-of-heaven is fast-growing, reaching up to 80 feet in the sky, adorned with compound leaves with 10 to 27 pointed leaflets. Underground, its robust root system can extend as far as 50 feet.

It knows no bounds, whether grassy or paved, and will grow between cracked slabs of concrete or through retaining walls, said Jessica George, Vancouver urban forestry education and outreach coordinator. This threat soon becomes tenfold more wicked, as a parent tree will shoot up dozens of sprouts if it is damaged or improperly removed.

In Portland, a resident may need to completely retrofit a home because a tree-of-heaven shifted the framework of its basement, as reported by KOIN 6 News.

Furthermore, tree-of-heaven’s roots, bark and leaves secrete chemicals that inhibit the growth and reproduction of plants nearby. Spotted lanternfly, an invasive insect that feasts on agriculturally significant crops, uses the tree as a host site, said Jeff Kessenich, urban forestry commissioner.

As the story goes, tree-of-heaven’s name is loosely related to its mysterious ability to grow abundantly, leading some to associate a heavenly power to it, according to Susan Sanders, a former urban forestry commissioner. Regardless of the tale’s truthfulness, the title rolls off the tongue more smoothly than its scientific name, ailanthus altissima — directly translating to “tallest sky tree.”

But for clarity’s sake, it’s also commonly (though unofficially) known as a harbinger of chaos.

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“You don’t want this thing around your house,” Sanders said.

Tree-of-heaven dots northeast and central China, where it’s native.

Hailed as a fast-growing shade tree, tree-of-heaven first dug its roots in Philadelphia during the late 1700s after being hauled from England, where it was previously introduced, according to Pennsylvania State University. About a century later, immigrants introduced the tree along the West Coast.

Tree-of-heaven wasn’t always rebuked as a menace to urban infrastructure and greenspaces, and admiration of the tree isn’t baseless.

Once established in the U.S., tree-of-heaven was widely cultivated by nurseries and tree enthusiasts for its ornamental appearance and its ability to develop quickly in adverse conditions, casting large patches of cool shade, Sanders said. A farmer in Eastern Washington, for example, would happily seek refuge at the base of its trunk rather than be exposed to relentless sun in expansive fields.

The tree has even been referred to as a symbol of endurance, a viewpoint popularized in 1943 by Betty Smith’s book “A Tree Grows in Brooklyn.”

Despite its cooling and allegorical contributions, tree-of-heaven still poses harm.

Removal isn’t a simple undertaking. It requires a deliberate approach, though it can be done professionally or individually. And it requires patience.

Arborists will typically remove most of the tree-of-heaven — leaving behind only its stump — and recommend treating it with an herbicide on a routine basis, according to Cascade Tree Works. Then they will come back to grind the stump and all its roots.

Herbicide timing is crucial, usually between July and October. During this window, the tree pulls nutrients into its root system for winter storage and, with it, whatever chemical is applied, Kessenich said.

If a stump isn’t treated with an herbicide, the tree will continue to sprout.

As a self-described environmentally keen gardener, Sanders avoids using chemicals and unnecessarily stripping away vegetation. But tree-of-heaven is a different breed.

“This is the exception,” she said.

The cost to remove any tree depends on its size and location, but tree-of-heaven’s elimination is rigorous and can be expensive, easily topping $1,000, Sanders said. Not all homeowners can make these investments, she added, leading groups to provide support, such as the Watershed Alliance of Southwest Washington’s neighborhood micro-grant program.

Kessenich urges community members to download the EDDMapS app to report local tree-of-heaven sightings, which will ping him to follow up and confirm. Doing so will help urban foresters create strategies to control tree growth and, ideally, prevent a spotted lanternfly infestation.

Report a tree

Tree sightings can also be reported at www.eddmaps.org or www.invasivespecies.wa.gov. For more details on Vancouver’s invasive trees, visit www.cityofvancouver.us/publicworks/page/guide-invasive-trees-city-vancouver.

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This story was made possible by Community Funded Journalism, a project from The Columbian and the Local Media Foundation. Top donors include the Ed and Dollie Lynch Fund, Patricia, David and Jacob Nierenberg, Connie and Lee Kearney, Steve and Jan Oliva, The Cowlitz Tribal Foundation and the Mason E. Nolan Charitable Fund. The Columbian controls all content. For more information, visit columbian.com/cfj.

Columbian staff writer