Common Tansy (Tanacetum vulgare) pollen. The strongly aromatic leaves of Common Tansy are finely divided into fernlike segments. The flowers are yellow buttons in flat-topped clusters. The plant contains a monoterpene called thujone. It is now illegal to sell this herb as food or medicine but traditionally, cold leaf tea was used to treat dyspepsia, flatulence, jaundice, worms, and suppressed menses. Tansy is an antispasmodic and antiseptic. It may cause dermatitis.