TANSY, Tanacetum vulgare L. 1, plant in flower; 2, root system showing rhizome; 3, section of a flower head; 4, seed. Perennial, reproducing by seed and short rhizomes. Root system strong, fibrous. Stems stout, erect, smooth or slightly hairy, 1 to 4 feet (0.3 to 1.2 m) tall, unbranched, except for the flowering portion. Leaves alternate, compound with oblong segments having toothed edges, smooth or nearly so, lower leaves sometimes 12 inches (30 cm) long. Flower heads numerous, button shaped, about 1/2 inch (1.3 cm) in diameter, composed of many small yellow ray flowers, in a flat-topped cluster at the top of the stem. Seed flat, about 1/16 inch (1.5 mm) long, 5-angled, yellowish-brown, tipped with small scales. Found along roadsides, in gardens and waste places. The plant has an unpleasant odor.