Urtica urens L.

Within the flora, Urtica urens is most abundant in California and in eastern Canada. The Shuswap used it medicinally for sweatbaths and for pain from rheumatism (D. E. Moerman 1986).

Wright (in 1899) and Handel-Mazzetti (in 1929) reported this species from Zhejiang, in SE China; however, we have seen no material from there. If present in Zhejiang, the plants must be naturalized.

Herbs , annual, with taproot, 1-8 dm. Stems simple or branched, erect. Leaf blades elliptic to broadly elliptic, widest near middle, 1.8-9 × 1.2-4.5 cm, base cuneate, margins coarsely serrate, serrations often with lateral lobes, apex acute; cystoliths rounded. Inflorescences spikelike or paniculate. Flowers unisexual, staminate and pistillate in same inflorescence, subsessile to short-pedunculate. Pistillate flowers: outer tepals ovate, 0.5-0.7 mm, inner tepals broadly ovate, 0.6-0.9 × 1.2-1.4 mm. Achenes ovoid, 1.5-1.8 × 1.1-1.3 mm. 2 n = 24, 26.

Herbs annual. Stems branched, 10-60 cm tall, sparsely puberulent and somewhat densely armed with stinging hairs; lower internodes 4-7 cm, upper internodes 1-3 cm. Stipules free, narrowly triangular, 1-2.5 mm, ciliate; petiole 1-2.5 cm, puberulent, sparsely armed with stinging hairs; leaf blade broadly elliptic, sometimes ovate or obovate, 1.2-6 × 0.6-3 cm, 5-veined, often subglabrous except for sparse stinging hairs on both surfaces, base broadly cuneate or rounded, margin 6-11-dentate, apex obtuse-rounded; cystoliths punctiform, distinct adaxially. Inflorescences containing proximal female flowers and distal male flowers, spicate, 0.5-2.5 cm. Male flowers short pedicellate, in bud ca. 1.2 mm; perianth lobes connate 1/2 of length, puberulent. Female flowers: perianth lobes connate at base, dorsal-ventral lobes ovate, equaling achene, often with 1 stinging hair on dorsal rib, sparsely setulose along margin, lateral lobes ovate, ca. 5 times as small as others. Achene brownish gray, ovoid, compressed, 0.8 mm, verrucose, invested by persistent perianth lobes. Fl. May-Jul, fr. Aug-Sep.

introduced; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Calif., Conn., Fla., Ill., Iowa, Maine, Mass., Mich., Mo., Nev., N.H., N.Mex., N.Y., Okla., Oreg., Pa., R.I., S.C., Tex., Vt., Wash.; Eurasia.

Flowering spring-summer.

Waste places, roadsides, pastures, barnyards, cultivated fields, rich woodlands; 0-700m.

Forest margins, roadsides, near villages; 500-1000 m in N China, 2800-2900 m in SW China. Liaoning, Qinghai, Xinjiang (Altay region), S Xizang [Africa, Asia, Europe, very widely distributed in temperate regions and tropical highlands].