Common Wormwood

Grown as a medicinal plant, most commonly as a vermifuge, Artemisia vulgaris is widely established in eastern North America and is often weedy in disturbed sites. Populational differences in morphologic forms are reflected in size of flowering heads, degree of dissection of leaves, and overall color of plants (from pale to dark green), suggesting multiple introductions that may date back to the first visits by Europeans. It is tempting to recognize the different forms as subspecies and varieties; the array of variation in the field is bewildering. If genetically distinct forms exist in native populations, the differences appear to have been blurred by introgression among the various introductions in North America. A case could be made for recognizing var. kamtschatica in Alaska based on its larger heads and shorter growth form; apparent introgression with populations that extend across Canada confounds that taxonomic segregation.

A highly polymorphic and widespread species in which a number of infraspecific taxa have been recognized. The infusion of leaves is said to be given in fever. The tomentum is used as moxa.

Perennials, (40–)60–190 cm, sometimes faintly aromatic (rhizomes coarse). Stems relatively numerous, erect, brownish to reddish brown, simple proximally, branched distally (angularly ribbed), sparsely hairy or glabrous. Leaves basal (petiolate) and cauline (sessile), uniformly green or bicolor; blades broadly lanceolate, ovate, or linear, (2–)3–10(–12) × 1.8–8 cm (proximal reduced and entire, distal pinnately dissected, lobes to 20 mm wide), faces pubescent or glabrescent (abaxial) or glabrous (adaxial). Heads in compact, paniculiform or racemiform arrays (10–)20–30(–40) × (5–)7–15(–20) cm. Involucres ovoid to campanulate, 2–3(–4) mm. Phyllaries lanceolate, hairy or glabrescent. Florets: pistillate 7–10; bisexual (5–)8–20; corollas yellowish to reddish brown, 1.5–3 mm, glabrous (style branches arched-curved, truncate, ciliate). Cypselae ellipsoid, 0.5–1(–1.2) mm, glabrous, sometimes resinous. 2n = 18, 36, 40, 54.

A perennial, large, basally suffruticose shrub with several, closely growing, erect, simple cinereous or tomentose to glabrous, striate to shallowly grooved, reddish-tinged, (30-) 50-18 (-200) cm tall stems from the upright, 1.5-2 cm thick rootstock. Leaves densely whitish arachnoid hairy beneath, green and sparsely hairy to glabrous above, basally articulate; basal leaves petiolate, lamina broadly ovate, 5-12 (-15) x 3-6 (-8) cm, unipinnatisect into elliptic-ovate, pinnatifid primary segments with acute lobes; middle and upper stem leaves sessile to subsessile, deeply pinnate; uppermost in floral region undivided, lanceolate, entire, acute. Capitula heterogamous, numerous, subsessile, oblong, 3-4 x c. 2 mm, erect to ± nodding, in 10-40 x 5-25 cm, broadly pyramidate panicle with 5-20 cm long, upwardly directed primary and secondary branches. Involucre 4-seriate, phyllaries greyish arachnoid pubescent outside; outermost ovate, 1.5 x c. 1 mm, narrowly scarious on margins, acute; inner elliptic-oblong, c. 2 x 1.75 mm, broadly pale scarious margined, obtuse. Receptacle glabrous, hemispherical. Florets 10-30, yellow with reddish tinge; marginal florets 5-10, female, fertile, with 1.75-2 mm long, bidentate, glandulose corolla tube; disc florets 5-20, bisexual, fertile, with 1.5-2 mm long, narrowly tubular-campanulate 5-toothed glandulose corolla. Cypselas light brown, c. 1 mm long, finely striate.

Distribution: North Africa, Europe eastwards to Caucasia, Turkestan, Siberia, Iran , Afghanistan, Pakistan, N. W. India; introduced and naturalised in N. America.

Fl. Per.:August-November.

Artemisia opulenta Pampanini; A. vulgaris var. glabra Ledebour; A. vulgaris var. kamtschatica Besser

A. superba Pamp. in Nuov. Giorn. Bot. Ital. n. s. 36: 473. 1930.