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Biennial, with a yellow composite (sunflower) type flowerhead with 10 to 15 ray petals. Flowering occurs from late June through September.
Tansy ragwort is toxic to big game animals and livestock. The toxicity is caused by several alkaloids which produce irreversable liver damage. The high rate of seed production and long viability of seeds means a long term commitment is required to eradicate an established infestation.
Spring conrtol efforts should use a selective herbicide appropre for the site. Blooming plants can be hand-pulled effectively in small sites. Plants may regenerate from root fragments.
A seed head fly is established in the Blue Mountains, other agents, so successful in Western Oregon, have not survived the harsh winters in Eastern Oregon. No current effort is being made to solve this problem.