Common tansy (Tanecetum vulgare L.), a pungent smelling perennial herb, was brought to the United States from Eurasia for horticultural and medicinal purposes. The plant reproduces by both seed and creeping roots. Stems are erect, brown or purplish-red in color, and dotted with glands. Mature plants grow from 2 to 5 feet tall. Fern-like leaves are alternate and deeply divided into numerous, individual leaflets with toothed margins. Flowering occurs from July to the fall, varying by location. Flowers are yellow and button-like without petal-like ray florets. They appear in dense, flat-topped clusters at tops of the plant. Seeds are yellowish-brown, 5-angled achenes, without pappus. Common tansy is distinguishable from tansy ragwort (Senecio jacobaea), which is non-aromatic and has ray florets and seeds with pappus. Common tansy plants prefer full sun and good subsoil moisture, and commonlyinvade disturbed areas, pastures, ditch banks, and riparian areas. This prolific plant contains alkaloids and is potentially toxic to both humans and animals, although cattle and horses seldom graze the bitter plant once it matures. This aversion allows common tansy to out compete desirable pasture plants.

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