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Tansy Ragwort

(Senecio jacobaea)

Common Names

tansy ragwort, tansy butterweed, ragwort, stinking willie


A beautiful plant, tansy ragwort is a biennial plant or short-lived perennial in the sunflower family. This plant germinates in the fall or early winter, lives through the following year as a rosette, then dies the next year after producing flowers and seeds. Rosettes of this plant have ten to twenty leaves with cottony, web-like hairs that are directly attached to the main stem. Lower leaves can be up to ten inches long, are irregularly lobed into leaflets with the leaflets being lobed again. Leaves are alternate, appear ruffled, have rounded tips, and decrease in size up the stem. Tansy generally grows from one to three feet in height, but with the right conditions, may grow up to six feet. The ray, daisy-like flowers can be a half an inch long, and the flower heads have a disk with thirteen petals (usually). Flowers are clusted at the end of the stems.  Seeds have a white pappus and can be carried along by the wind, resulting in rapid spread. A single large tansy ragwort plant can produce up to 200,000 seeds.  The root system consists of extensive light-colored roots that spread and produce shoots when stimulated by mechanical treatment.

Key Features

Daisy-looking flower heads with thirteen petals, ruffled leaves and cottonly web-like hairs that attach from the leaves to the stems.


Tansy Ragwort prefers to grow in disturbed areas; it is often found on waste places, roadsides, pastures, hayfields, creek bottoms, pastures, after forest fires and forest clear-cuts.

Currently found in the following counties:

Flathead, Judith Basin, Lincoln, Mineral, Sanders, Toole


Interesting Facts

If this plant is prevalent in livestock pastures, be aware that ingestion of this plant is one of the most common causes of poisoning in cattle and horses. Even when cured in hay, the plant still contains toxins, and even milk and honey can be contaminated with tansy ragwort toxins after cattle and bees consume the plant.

Commonly Confused Plants

Dryland ragout (Seneca eremophilus) resembles tansy ragwort, but the leaf tips are pointed rather than rounded.

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Photo credits:Photo Credits: Dan Williams; Richard Old, XID Services, Inc.,; Eric Coombs, Oregon Department of Agriculture,; Leslie J. Mehrhoff, University of Connecticut,