Tanacetum L.
Annual or perennial herbs, often rhizomatous. Lvs simple, entire to 1-3-pinnatisect, alternate. Capitula in corymbs, or rarely solitary, terminal, usually pedunculate; involucral bracts in 3-4 rows, often with membranous margins. Receptacle flat; scales 0 or few. Outer florets usually ♀ (sometimes all florets ⚥), ligulate or ligule much reduced, yellow, white or pink; inner florets usually ⚥ and tubular, transformed into ligulate florets in double forms. Achenes all similar, cylindric or clavate, sometimes with many small glands but otherwise glabrous, 3-10-ribbed; pappus a small toothed or lobed corona.
Key
c. 70 spp., Europe, temperate Asia. Naturalised spp. 2.
Tanacetum is part of the Chrysanthemum complex and is sometimes treated within Chrysanthemum sens. lat. Achenes of the 2 naturalised spp. are similar (see, T. parthenium, Fig. 17).
