tansy

Any of about 150 species of strong-smelling, poisonous herbs, especially common tansy (Tanacetum vulgare), of the aster family (Asteraceae), native to the northern temperate zone. T. vulgare has button-shaped yellow flower heads of disk flowers (no ray flowers) that are arranged in a flat-topped cluster, deeply cut leaves, and many stems. It is sometimes cultivated in herb gardens and was formerly used in medicines and insecticides. See also chrysanthemum.

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