Tansy - Tanacetum vulgare

Tansy is a flowering herb with finely divided compound leaves and yellow, buttonlike flowers. It has a stout, somewhat reddish, erect stem, usually smooth, 50-150 cm tall, and branching near the top. The leaves are alternate, 10-15 cm long and are pinnately lobed, divided almost to the center into about seven pairs of segments or lobes which are again divided into smaller lobes having saw-toothed edges, thus giving the leaf a somewhat fernlike appearance. The roundish, flat-topped, buttonlike, yellow flower heads are produced in terminal clusters from mid to late summer. The scent is similar to that of camphor with hints of rosemary. The leaves and flowers are said to be poisonous if consumed in large quantities. The plant's volatile oil is high in thujone, a substance found in absinthe that can cause convulsions. Some insects, notably the tansy beetle, have evolved resistance to tansy and live almost exclusively on it.