Feverfew

Tanacetum parthenium is widely cultivated throughout North America.

Perennials, (20–)30–60(–80) cm. Stems 1–3+ (ridged), erect, branched (usually glabrous proximally, puberulent distally). Leaves mainly cauline; petiolate; blades ovate to rounded-deltate, 4–10+ × 1.5–4 cm, usually 1–2-pinnately lobed (primary lobes 3–5+ pairs, ± ovate), ultimate margins pinnatifid to dentate, faces (at least abaxial) usually puberulent, gland-dotted. Heads 5–20(–30) in corymbiform arrays. Involucres 5–7 mm diam. Ray florets 10–21+ (more in "doubles"), pistillate, fertile; corollas white, laminae 2–8(–12) mm. Disc corollas ca. 2 mm. Cypselae ± columnar, 1–2 mm, 5–10-ribbed; pappi 0 or coroniform, 0.1–0.2+ mm. 2n = 18.

Perennial or annual, pungent aromatic herbs, with many, ± puberulous, striate-angled, erect, 20 – 60 (-80) cm tall, densely leafy stems from ± woody rootstock with fibrous roots. Leaves radical or cauline, punctate glandular on both sides, usually yellowish-green, on slender, canaliculate, 2.5 – 8 cm long petioles, laminas ovate-oblong, 2 – 7 (-8) cm long, 1.5 – 5 cm broad, 1-2-pinnatisect to pinnatipartite into obtuse or subacute ultimate segments, the upper leaves reduced gradually in size, on shot petioles or sessile, glabrous or sparsely to moderately pubescent. Capitula radiate, heterogamous, few to several, upto 20 (-30) on 2 –3.5 cm long peduncles, in terminal dense corymbs borne on 2 – 13 (-15) cm long floral axis. Involucre hemispherical, 2-3-seriate, phyllaries imbricate, outer lanceolate, c. 1.5 mm long, inner oblong-oblanceolate, 3 – 4 (-5) mm long, sparsely pubescent or glabrescent, finely scarious and shortly lacerate at the apices. Receptacle convex or occasionally flat. Ray-florets 5-12, female, with oblong, 5 – 6 x 2 – 3 mm, obtusely 3-lobed, white ligules. Disc-florets yellow, with tubular-infundibuliform, 5-toothed, 2.5 – 3 mm long corolla tube. Cypselas oblong, 1 – 1.5 mm long, grayish-brown, with 6 – 8 white ribs and sessile glands, flattish. Pappus coroniform, irregularly lobed, or rarely evenly lobed, 0.1 – 0.5 mm long.

Distribution: N Africa, SE and E Europe, SW Asia from Turkey to Caucasus, Iran, Afghanistan, Pakistan (Baluchistan, N.W.F. Province); Kashmir and Central Asia; also widely naturalized in many countries.

Fl. Per.: July-September.

Waste places, banks of streams, sometimes in forest shade or on rock edges, from sea level to 2500 m.

Matricaria parthenium Linnaeus, Sp. Pl. 2: 890. 1753; Chrysanthemum parthenium (Linnaeus) Bernhardi

Matricaria parthenium L., Sp. Pl. 890. 1753; Chrysanthemum parthenium (L.) Bernh., Syst. Verz. Erf. 145 (1800); A. B. Jackson in Kew Bull. 1937:393. 1937; R. R. Stewart, l. c. 732; Pyrethrum parthenium (L.) Sm., Fl. Brit. 2: 900. 1800; Boiss., Fl. Or. 3: 344. 1975; Post, Fl. Pal. ed. 2, 2:62. 1933; Tzvelev in Schischk. & Bobrov, Fl. USSR 26. 195. 2000. (Engl. transl.).