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Butterflies, beware the wort

New invader 'swallow wort' threatens region

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BOLTON -- Officials are taking steps to prevent the spread of a plant spotted last week along the shoreline of Lake George.

The invasive species — black swallow-wort — is a twining vine that smothers other plants and is thought to threaten the monarch butterfly population. It was found near Rainbow Beach Road in Bolton.

Emily DeBolt, outreach coordinator for the Lake George Association, said she and members of the Rainbow Beach Association spotted the plants at Rainbow Beach on Basin Bay. They saw it during a trip to look at the growth of a native plant buffer the homeowners association had planted to manage stormwater runoff.

“It has a very distinct flower, like a black star. I knew right away that, unfortunately, it was black swallow-wort,” DeBolt said.

The plant, native to Spain and Portugal, is seen as an emerging threat in the Adirondack Park, with about half a dozen reported sightings. Its leaves are glossy, sometimes black and sometimes pale, and it produces small flowers, maroon to pale pink, in late May through July. Seed pods are smooth, slender and pointed. They split open to release downy seeds that spread in the wind.

The plant’s pods mimic milkweed pods, where monarch butterflies lay eggs.

Because of the confusion, female monarchs lay eggs on the swallow-wort, and the larvae don’t survive.

“Milkweed is the host plant they have to lay eggs on. When they hatch and feed on these (swallow-wort) leaves, they die,” DeBolt said.

According to the Adirondack Park Invasive Plant Program website,, swallow-wort vines push out large areas of native plant species and threaten forest regeneration. According to the website, the plant is somewhat toxic, making it poor forage for wildlife such as deer.

The pale swallow-wort vine has been a problem in central and western New York while the black swallow-wort has posed threats to other plant life in New England in states such as Massachusetts.

Brendan Quirion, a coordinator for the invasive plant program, said swallow-wort has been found in Elizabethtown, Ticonderoga, and Willsboro. The plant is prevalent in Malone and much of St. Lawrence County outside the Adirondack Park, he said.

He said an infestation of pale swallow-wort emerged in the town of Ohio, too.

“It is one of the top new and emerging terrestrial invasive plants in the park and is spreading very quickly wherever it becomes established. It is also called dog strangling vine and for good reason. It easily outcompetes other native vegetation, creating dense mats that cover fields and the forest floor,” Quirion said.

The local sighting has officials headed out Tuesday to do they best they can to get rid of it.

LGA staff and members of the Rainbow Beach Association, in coordination with the Adirondack Park Invasive Plant Program, will dig it up, record its GPS coordinates, and mark the area with flags so they can continue to monitor the site and make sure more plants don’t grow.

“When we get out there, hopefully we won’t find more,” DeBolt said.

Now is the best time to spot invasive species, since many of them are in flower. Anyone who sees swallow-wort vine should take a photo of it, make note of its location and report it to the LGA at 668-3558 or, for the broader Adirondacks area, the APIPP, at 576-2082.


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