Report this monarch-threatening invasive vine if you see it in N.B., conservationist urges

Conservationists are urging people to be on the lookout for an invasive vine that's harming the monarch butterfly population and the general ecosystem. It's called dog-strangling vine and it's now been found in New Brunswick.

Monarch butterflies have distinctive orange and black markings with white dots on their wings' borders. Monarch sightings are a sure sign that summer is coming, as they migrate back to Atlantic Canada after wintering in Mexico.

The butterflies rely on milkweed for their reproduction. They lay their eggs on this common plant, and those eggs become caterpillars that eat only milkweed until they metamorphose into butterflies. 

Dog-strangling vine is in the same family as milkweed and is too similar-looking, according to Kristin Elton with the New Brunswick Invasive Species Council. The monarchs often mistake it for milkweed when lay their eggs, and when the eggs hatch there's nothing to eat.

"The caterpillars ultimately die because they have no food," Elton told Shift New Brunswick.

Also known as the European swallow wort, the plant doesn't actually strangle dogs, Elton said, but it does have an extreme advantage over the native ecosystem. 

It can grow up to two metres tall and produces star-shaped pink or deep purple flowers. It also produces long bean-shaped pods that contain seeds with fluffy tufts that break open and spread in the wind.

It's a very vigorous plant and will wrap around things and suppress other growth, she said. It also releases chemicals into the soil that prohibit growth of other species.

"It's a very impressive plant, it's just one that we don't want here," Elton said.

On top of that, deer tend to avoid this plant because it produces toxic sap.

And while it doesn't quite have nine lives, it's more difficult to kill than a regular weed. 

Elton said if you see it around your property, dig it up, but don't just throw it on your compost pile. Even after it's dug up, it can still spread seeds. That's why it should be contained in a black garbage bag, sealed well and left in the sun for a few days to decompose.

According to the Nature Conservancy of Canada, the vine arrived in Canada with European settlers approximately 120 years ago. 

It has generally been found in southern Ontario, but it's been recently spotted in New Brunswick, including in Saint John. It's also been spotted in Nova Scotia, Elton said, but the exact extent of its spread is unknown.

"We're missing a lot of data. We know that it's here, but we don't really know the extent of exactly where it is," she said.

That's why she's calling on the public to learn what the plant looks like and report it using iNaturalist, an online tool and app.

"You just take a photo, upload it, it'll show where the location is. You can input the information if you know what the plant is. If you're not sure, it can do its magic [artificial intelligence] thing and give you a guess as to what species it is," she said.