3. Tanacetum vulgare L. (common tansy, golden buttons)

Pl. 228 e–g; Map 957

Plants producing rhizomes. Stems 40–150 cm long, moderately pubescent with short, curly hairs when young, becoming glabrous or nearly so by flowering time. Leaves 3–20 cm long, the basal leaves usually absent by flowering time, short-petiolate to sessile. Leaf blades pinnately compound or deeply pinnately lobed, oblong-obovate to elliptic in outline, the primary leaflets or lobes 9–21 (with short wings or reduced, accessory lobes between them), these pinnately lobed, narrowly elliptic to lanceolate or oblong-lanceolate, rounded to more commonly bluntly pointed at the tip, broadly sessile or short-angled at the base, the margins otherwise sharply toothed, both surfaces moderately to densely glandular but otherwise glabrous or nearly so at maturity. Heads usually discoid. Involucre 3–7 mm long, broadly and shallowly cup-shaped, the bracts in 3–5 series, the main body narrowly oblong-lanceolate to triangular-lanceolate, tapered to a conspicuous, thin, papery tip, the margins also thin and nearly transparent, the outer surface glandular and hairy. Ray florets absent or the marginal florets rarely pistillate, somewhat zygomorphic, but inconspicuous and not markedly enlarged, yellow. Disc florets with the corollas 1.5–2.5 mm long. Pappus a short collar or crown or absent. Fruits 1.3–1.7 mm long, moderately to strongly 5-angled or 5-ribbed, those of the ray florets sometimes only 3-angled. 2n=18. July–September.

Introduced, scattered (native of Europe, Asia, introduced widely in North America). Tops of bluffs; also fencerows, roadsides, railroads, and open, disturbed areas.

Feverfew has been used medicinally to treat fevers and headaches, and as a tonic. However, Burrows and Tyrl (2001) noted that several cases of fatal overdoses have been documented involving ingestion of either a concentrated extract or a tea brewed from dried plants. An unusual mutant with irregularly undulate (crisped) leaf margins that is sometimes cultivated has been called f. crispum (L.) Hayek.