Noxious plant taking root in Oakdale, Washington County

Black swallow-wort. (courtesy of Minnesota Department of Natural Resources)

Amy Felegy

staff writer


The black swallow-wort, an invasive and noxious vine to monarch butterflies and native plants, has made its way to Oakdale and other portions of Washington County, according to a Sept. 11 release from the University of Minnesota Extension.

It’s the first time the county has seen the plant, which also goes by the name of black dog-strangling vine.

After seeing a strange-looking vine in her backyard this summer, Janelle Dahman reported it to the Minnesota Department of Agriculture. After some research, Dahman, a Master Gardener and garden center supervisor at Bachman’s, knew just how tricky the plant could be to eradicate.

“It’s probably the worst case scenario,” said Dahman, who lives in the Longfellow neighborhood of Minneapolis. Through her getting the word out to other Master Gardeners, the plant was spotted in Oakdale.

It’s made significant appearances on the upper East Coast and in states like Michigan, Illinois, Wisconsin, Pennsylvania and Ohio. It spreads not only by roots, but by seeds -- they go airborne and can travel long distances.

The plant looks a whole lot like milkweed, making it difficult to distinguish for butterflies and gardeners alike. It’s even in the milkweed family, but when monarchs lay their eggs on it the caterpillars can’t survive due to the plant’s toxic nature.

This is why plant experts say it’s so important for property owners, renters and anyone who comes in contact with plants to watch out for the black swallow-wort and follow a specific removal procedure.

Angela Gupta, a forestry extension educator at the University of Minnesota, asks anyone who sees the shiny green vine with pods to report it as soon as they first see the plant. It’s on the Minnesota Noxious Weeds Eradicate List, which experts say should be taken seriously. 

“State statute requires things on the Eradicate List be destroyed,” Gupta said. “These are very problematic.”


Early stages 

Monika Chandler, a plant protection specialist at the Department of Agriculture, said the vine was first introduced to Harvard’s botanical garden from Europe in the late 1800s and can be seen across greater Massachusetts and Connecticut today. In Boston, a group called the Cambridge Pod Squad still attempts to remove the black swallow-wort despite tall odds.

Luckily, after Dahman’s discovery led to more sightings in Oakdale and across the county, there are only a few other known infestations here and there.

“In Minnesota, we’ve had a heads-up that it’s an invasive plant and causes trouble,” Chandler said.

This trouble, Chandler said, includes forcing out native plants like milkweed and others.



Eliminating the black swallow-wort is both complicated and unlikely, Dahman said. 

“It’s still growing, so every time I go out there and I have to mow the lawn, I’m pulling it,” she said. “[It’s] the best I can do before the seed pod explodes.” 

“Hopefully it will eventually exhaust it of any energy and [it] won’t come back,” she added, saying that keeping it at bay is the next-best solution. 

Since the county is new to dealing with the plant, removal tactics should be strictly followed, plant experts say. Those who find the black swallow-wort shouldn’t compost it because backyard composts typically don’t get hot enough to destroy the plant. 

Washington County staff said a public compost is set to be installed for county and residential use on Oct. 1 in Hugo.

Digging up the roots to remove the plant completely has been effective in removal, according to the University of Cambridge. Chemical methods like Round Up Pro and Garlon 3A have also been used to successfully control swallow-wort. 

For now, spreading awareness may be the key to stopping the spreading vine. Dahman said she heard a radio program about the black swallow-wort and hopes that means more people are now aware. She also said she hands out brochures of information about the plant at her store and throughout the neighborhood, but eradicating the plant is quite the undertaking.

She said it requires Conservation Corps removal teams to get the approval of every yard they want to clear, and it often includes non-organic pesticides.

“Even if they could get the Conservation Corps to help, it couldn’t happen this year,” Dahman said. “Logistically it wouldn’t be able to contact everybody.”

Experts ask those who see the invasive plant to report black swallow-wort by downloading the Great Lakes Early Detection Network app and following the reporting process. Other options for reporting include visiting or contacting the Department of Agriculture by emailing or calling 1-888-545-6684.

Per the University of Minnesota Extension program, early fall is the ideal season for removing the plant because the seed pods haven’t yet burst and dispersed seeds.

For those not interested in paying attention to noxious weeds, Dahman has one piece of advice.

“I get that not everybody finds gardening fun like I do,” she said. “Just be aware of what’s going on in your own yard.”


Amy Felegy can be reached at or 651-748-7815.

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