Alberta (Rural Roots Canada) – Canada thistle has won the top spot on Alberta’s most-reported invasive species list for the second year in a row. In all, 409 reports were submitted through the EDDMapS tracking system in 2025.

The Alberta Invasive Species Council released the rankings, showing Canada thistle leading over dalmatian toadflax (391 reports) and spotted knapweed (306 reports).

“Canada thistle has been here for a long, long time,” said Megan Evans, executive director of the Alberta Invasive Species Council. “It’s really had an opportunity to spread.”

The plant, also known as creeping thistle, is not native to Canada and was one of the first species listed under Alberta’s Weed Control Act. What makes it particularly hard to deal with is its extensive underground root system. It can survive even when the above-ground plant is removed.

“The seeds in Canada thistle aren’t always super viable. It’s really those underground roots that are really the hard part to kill,” Evans explained.

The impact on Alberta’s agricultural sector is huge. Invasive species cost the province roughly $2 billion annually, with the majority of that cost the result of invasive plants like Canada thistle.

“When they come into these agricultural systems, if it’s like a pasture where cows are grazing the vegetation, or if it’s a crop field, the Canada thistle pops up, and that’s going to impact their yields,” Evans said.

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Controlling the plant requires different approaches depending on whether it’s in pastures, crops or ditches, Evans said. Methods include removing above-ground growth and applying herbicide to target the roots at key times of year.

The rankings come from reports submitted through EDDMapS, an app and online platform where anyone can document invasive species sightings. The council verifies reports using submitted photos and forwards them to local authorities for follow-up.

“It’s really useful, like in more natural areas or parks or things like that where maybe the manager, the area land manager doesn’t know about it,” Evans said.

While farmers already know about Canada thistle on their land, public reports from parks, trails and roadsides help track the species’ spread and alert land managers who might not realize they have a problem.

To encourage participation, the council is awarding the Big EDD Belt, a wrestling-style championship belt, to whoever submits the most reports in a season. The winner will get their name engraved on the belt and free registration to the council’s annual conference, happening March 11-12 in Olds.

Evans said Albertans should stay vigilant about emerging threats.

“It’s really a death by a thousand cuts on any native plant community,” Evans said.

The council encourages Albertans to download the free EDDMapS app and report invasive species year-round. Even dried plant skeletons in winter can be identified and tracked.