- Senecio jacobaea
Tansy ragwort (Senecio jacobaea) is a biennial to short-lived perennial. Considered noxious under the BC Weed Control Act, tansy ragwort grows in grazed pastures, hay fields, vacant non-crop lands, roadsides, clear cuts, and other disturbed areas. Currently found in the central Fraser Valley, central to southern Vancouver Island, the Gulf Islands, and the east side of the Okanagan Valley between Kelowna and Penticton.
Tansy ragwort has bright yellow daisy-like flower heads arranged in a dense, flat-topped cluster at the top of the stem. Each flower head has 10-15 petal-like ray flowers surrounding yellow disk flowers. Bushy plants have a ragged appearance, with ruffled, deep-cut leaves and purplish stems. Tansy ragwort grows to 0.2-1.2 metres in height at maturity.
Tansy ragwort reproduces mostly from seeds blown in the wind, but regeneration of shoots can occur from crown buds, root fragments, and intact roots. Tilling, grazing or other disturbance promotes seed germination and spread. A single plant can produce 150,000 seeds that remain viable in the soil for up to 15 years. Most new growth occurs within 10 metres of the original infestation. Seeds can be transported in soil carried on equipment and vehicles, as well as by people and livestock. Tansy ragwort reduces forage production of pastures by up to 50%, and alkaloids in the plant taint honey produced by bees so that it is too bitter and off-color to market.
Warning: Tansy ragwort contains toxic alkaloids that can cause cumulative liver damage in cattle, deer, pigs, horses, and goats.