Alberta takes on hawkweed

Alberta has a new invader. It arrived stealthily, by unknown means, though it likely hitched a ride on construction equipment. Now it is poised to take over territory.

Such invasions are not unfamiliar to provincial weed specialists, but yellowdevil hawkweed is a formidable adversary.

There are no approved herbicides to control it, and the wily weed can spread in several different ways. Unchecked, it can form mats that choke out desirable pasture species.

Alberta Agriculture weed specialist Nicole Kimmel said the sighting of yellowdevil hawkweed in southern Alberta’s Crowsnest Pass this summer was the first discovery of this particular weed in Alberta.

However, yellowdevil hawkweed is a well known invasive throughout the United States Pacific Northwest and in British Columbia, so its arrival is not a surprise.

“We’ve been finding it in forested areas, in pasture grazing areas and along roadsides. It’s fairly versatile in its habitat preference,” Kimmel said in an Aug. 29 interview.

The weed likes disturbed soil. In fact, it likes it too much, as Kimmel discovered while trying to dig it up.

“They usually get a little testy and they spread a little bit more aggressively after any digging. We’re still working on control measures. Prevention is the key.”

There are many types of hawkweed, so identification isn’t easy. Kimmel said there are 12 invasive species and six or seven species native to Alberta.

“If it’s forming a mat, it’s really thick, then chances are it’s the invasive ones, because the native ones don’t usually reproduce by all three methods. They’re just seed producers as a general rule,” she said.

Those three methods include rhizomes, stolons and root buds.

“Where we’re concerned from an agriculture stance would be pasture and grazing areas, because once they’re in, they can get those mats and meadows of invasive hawkweed and they quickly out-compete. And they don’t offer a whole lot of forage value.”

Cattle will eat hawkweed, although it is not a preferred forage, nor is it toxic to animals, Kimmel added.

Yellowdevil hawkweed has small, dandelion-like flowers. Hairs on its stem help experts determine the species but identification is difficult.

Those who find yellowdevil hawkweed should contact an agricultural field man or range agrologist so the weed can be documented.

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