Tree of heaven, a noxious weed and invasive tree, is making an indelible mark on the Pacific Northwest — and confounding the officials attempting to control its spread.

“Something is definitely triggering more fecundity, and we’re not sure what it is,” said Beth Myers-Shenai, a noxious weed specialist at the Oregon Department of Agriculture.

A female tree of heaven can produce more than 300,000 seeds annually, and the trees can’t be removed via simple cutting methods. Their roots will sucker into the soil, resprouting as far as 50 feet from the parent tree.

When crushed, its leaves produce a smell comparable to rotten peanut butter.

The tree eventually spread to the Pacific Northwest, where it is commonly found along riverbanks and is especially prevalent along the Interstate 5 corridor and east of the Columbia Gorge, Myers-Shenai said.

“As a non-native to the northern U.S., it doesn’t have a natural enemy, so it doesn’t have any natural controls keeping it in check, like other native plants do,” Myers-Shenai said.

Tree of heaven was first added to ODA’s noxious weed list in 2013, as the weed became more prevalent across the state. It’s listed as a “B” weed — more intended to raise awareness about the plant than to control or eradicate it, given how widespread it is throughout the region, Myers-Shenai said.

Nevertheless, some jurisdictions have made attempts to combat the plant, like Wheeler County, Ore., home to the John Day River Basin.

Cassandra Newton is the district manager of the Wheeler Soil and Water Conservation District.

Newton submitted a grant application to ODA that would have attempted to eradicate tree-of-heaven in Wheeler County, but was denied.

“Compared to other areas in Oregon, we felt we had a small enough infestation that it was able to be eradicated,” Newton said. “In the Columbia Gorge area, or over near Umatilla (Ore.) on Highway 730, those infestations are so massive that you’re talking millions of dollars and multiple years of work.”

Newton did say the county has used some of its Bureau of Land Management funding to treat tree of heaven, in collaboration with ODA.

Complicating efforts to fight tree of heaven is the spread of the spotted lanternfly, which has been detected in at least 18 states as of 2023. The invasive insect can infest and destroy numerous crops, including stone fruit orchards and vineyards — and tree of heaven is its primary host.

While there have only been isolated sightings of the spotted lanternfly in Oregon and Washington, some officials say its arrival is a question of “when” — not “if.”

“It’s estimated that (spotted lanternfly) will be here in two to four years,” said Renee Hadley, the conservation district manager in Walla Walla County, Wash. “We don’t want to have it find the tree of heaven and propagate like crazy.”

Hadley recommended eradicating any tree of heaven within half a mile of orchards and vineyards to provide a future “buffer” against the spotted lanternfly.

While solutions for tree of heaven infestations are slim, a new approach could soon be introduced, said Joel Price, a biological control entomologist with ODA. Introducing the snout weevil, also native to China, could do significant damage to the tree — its larvae tunnel underneath the bark and help it become susceptible to disease. The weevil is currently in the federal permitting process, Price said

“There is an added importance to controlling both an invasive weed species and insect pest all at once,” he said.