3. Artemisia biennis Willd. (biennial wormwood)

Pl. 225 c, d; Map 943

Plants annual or biennial, with taproots, not or only slightly aromatic when bruised. Stems 30–150(–300) cm long, erect or ascending, glabrous but minutely glandular. Leaves 1–15 cm long, the basal and lower leaves often withered by flowering time, all the leaves short-petiolate to sessile, often with 2 or 3 pairs of small, linear, stipulelike lobes or leaflets at the base. Leaf blades 1 or 2 times pinnately compound or deeply lobed, lanceolate to ovate or obovate in outline, the main leaves with 7–11 primary lobes, the ultimate segments or lobes 0.5–3.0 mm wide, narrowly elliptic-oblanceolate to linear but not threadlike (except sometimes on the uppermost leaves), mostly sharply pointed at the tip, the margins toothed, both surfaces glabrous but minutely glandular. Inflorescences appearing densely and narrowly paniculate or spikelike with short, densely flowered branches, the heads sessile or nearly so. Heads with the central florets perfect and the marginal florets perfect or pistillate, thus all of the florets potentially producing fruits. Involucre 2–3 mm long, the bracts in 2 or 3 overlapping rows, the main body oblong-elliptic, glabrous but minutely glandular, with broad, thin, transparent margins and tip, these glabrous. Receptacle naked, without bristly hairs. Corollas 0.7–1.1 mm long. Fruits 0.7–0.9 mm long, narrowly ellipsoid-obovoid, mostly 5-nerved or finely 5-ribbed, somewhat flattened, reddish brown to brown, shiny. 2n=18. June–November.

Introduced, uncommon in Atchison County and the St. Louis and Kansas City metropolitan areas (native of the northwestern quarter of the U.S. and adjacent Canada, introduced widely but sporadically farther east). Banks of rivers; also railroads and open, disturbed areas.