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Tansy Ragwort Senecio jacobaea
Tansy ragwort is an invasive, toxic biennial weed from Europe most often found in pastures and along roads and trails. It is a Class B Noxious Weed in Washington State and control is required in selected counties in the state, including King County.
History and Impact
An invader from Europe, tansy ragwort was first seen in seaports in the early 1900's and is often spread in contaminated hay. When prevalent, tansy ragwort is one of the most common causes of poisoning in cattle and horses, caused by consumption of the weed found in pasture, hay or silage. Milk produced by affected cows and goats can contain toxins. Stock does not reject or avoid it in hay or silage; its poisonous alkaloids are unaffected by drying. Honey from tansy ragwort also contains the alkaloids.
Biology and Morphology
The plant's stem is stout, erect or slightly spreading, and may be branched; often groups of stems arise from the plant crown. A biennial plant, tansy ragwort usually germinates in fall or early winter, lives through the next year as a rosette, then dies the following year after producing flowers and seeds. Its leaves are dark green on top, whitish-green underneath, and have deeply cut, blunt-toothed lobes with a ragged/ruffled appearance. Flower clusters develop on stout, leafy elongated stems that grow up to 6 feet tall; each flower cluster is composed of many bright-yellow flowers with (usually) 13 petals. Its seeds have a white pappus and are wind-carried, resulting in rapid spread of tansy ragwort infestations. A single large plant may produce 150,000 seeds, which may lie dormant in the soil for as long as 15 years. The plant's fibrous system of coarse, light colored roots spreading from the crown can produce small adventitious shoots when stimulated by mechanical destruction or pulling.
Additional Tansy Ragwort Photos - click thumbnail for larger image
More Information on Tansy Ragwort (Senecio jacobaea)
Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact a staff member at the King County Noxious Weed Control Program, please call 206-296-0290 or by reach them by email.
The plant's stem is stout, erect or slightly spreading, and may be branched; often groups of stems arise from the plant crown. A biennial plant, tansy ragwort usually germinates in fall or early winter, lives through the next year as a rosette, then dies the following year after producing flowers and seeds. Its leaves are dark green on top, whitish-green underneath, and have deeply cut, blunt-toothed lobes with a ragged/ruffled appearance. Flower clusters develop on stout, leafy elongated stems that grow up to 6 feet tall; each flower cluster is composed of many bright-yellow flowers with (usually) 13 petals. Its seeds have a white pappus and are wind-carried, resulting in rapid spread of tansy ragwort infestations. A single large plant may produce 150,000 seeds, which may lie dormant in the soil for as long as 15 years. The plant's fibrous system of coarse, light colored roots spreading from the crown can produce small adventitious shoots when stimulated by mechanical destruction or pulling.
