There’s a killer loose on the Mountain. His name is Ragwort. That’s Tansy Ragwort to you, pal.

The invasive weed tansy ragwort has a long and deadly history in the Pacific Northwest. It is believed to have been brought here in the early 20th Century through ballast water from ships.

This noxious plant is dangerous to humans and livestock due to a poisonous
alkaloid in its tissue which causes liver damage when ingested, according to
Lisa Kilders, education and outreach program manager for the Clackamas Soil
and Water Conservation District.

“Horses and cows are especially susceptible to this poisonous weed with death
occurring after consuming 3 to 8 percent of body weight,” Kilders wrote in a
press release to The Mountain Times. “Humans can also be harmed from
tansy ragwort by consuming the plant, consuming livestock suffering from
liver damage ... by consuming animal products such as milk (made from liver
damaged cows), and honey (made with tansy ragwort nectar).”

Ragwort is an especially familiar sight in rural communities. It prefers a cool,
wet climate, well-drained soils and full to partial sun.

“You can see patches of tansy in pastures, fields, grasslands, vacant land,
waste places, horse trails, roadsides, rangeland, riparian areas, and clear
cuts,” Kilders wrote.

Tansy ragwort is a biennial, taking two years to complete its lifecycle. In its
first year, it appears as a ground-hugging rosette, transitioning in its second
year up to six feet in height. It blooms in late spring and early summer with
yellow flowers. The stems are green, sometimes with a reddish tinge, and the
leaves are dark green and ruffled.

Control methods
Rosettes should be dug up, removing the root. Because it is toxic, wear gloves
and protective clothing. Pulled plants should be bagged and placed in the
municipal waste.

Mowing is not a good control method. While it may prevent the plant from
immediately producing seeds, it also stimulates additional growth.

Insects have been introduced – most notably the Cinnabar moth – to help
control the invader. The caterpillars of the moth feed on the flowering ragwort
during the summer.

For information on how to control the tansy ragwort with chemical controls,
contact the WeedWise program at 503-210-6000.