Tansy Ragwort
Jacobaea vulgaris
Washington State Classification
Class B — Control Required (Designated)
Tansy ragwort is toxic and a threat to livestock and agriculture.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
It is a biennial or sometimes a winter annual or perennial herbaceous plant. As a biennial, tansy ragwort spends the first year in the rosette stage with dark green basal leaves that appear ruffled. During the second year, one or more flowering stems form. Disturbance, such as mowing, may cause the plant to behave as a perennial, appearing year after year.
Leaves
Leaves are twice divided, with petioles (leaf stems) on leaves near the base and without petioles toward stem tips. First year leaves in a basal clump (rosette). Second year leaves are alternate along the stem, 1.6 to 7.9 inches long by 0.8 to 2.4 inches wide.
Flowers
Flowerheads are in somewhat flat-topped clusters. Flowerheads yellow with many disk flowers and 13 ray flowers (which look like petals), overall having a daisy-like appearance. Flowerheads have around 13 bracts at their base with dark tips.
Fruit & Seeds
Seeds are sparsely hairy to glabrous (hairless and smooth).
Impact
Tansy ragwort is toxic and a threat to livestock and agriculture. All plant parts are toxic, with the highest amount of alkaloids in flowers then leaves, roots and stems. Toxic properties are a possible threat to humans through food chain contaminants. Find out more about tansy ragwort toxicity in our booklet: Protect Your Horses and Livestock From Toxic Plants on pages 23-24.
Ecology & Spread
Habitat
Tansy ragwort is readily found in open, disturbed areas such as roadsides, in pastures, fields and cleared forested areas. It is not particular to soil type. Please click here to see a county level distribution map of tansy ragwort in Washington.
Spread Mechanisms
Reproduction
Tansy ragwort usually reproduces by seed, although it can also reproduce vegetatively.
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Control Methods
Biological Control
- The tansy ragwort flea beetle, Longitarsus jacobaeae, larvae and adults are destructive to tansy ragwort. Larvae feed on and within the roots and the adults feed on leaves. The ragwort seedhead fly, Botanophila seneciella, larvae feed within seedheads, often destroying all of the developing seeds. The cinnabar moth, Tyria jacobaeae, caterpillars can completely defoliate tansy ragwort. Unfortunately the cinnabar moth can also feed on native and horticultural species of Senecio and Packera so further redistribution of the moth is discouraged in many areas. If you have questions or are looking for more information about these biological control agents of tansy ragwort, please visit WSU Extension Integrated Weed Control Project.