苎麻 zhu ma

Subshrubs or shrubs simple or few branched, 0.5-1.5 m tall; upper stems, branchlets, and petioles densely patent hirsute, appressed strigose or only strigose. Monoecious. Leaves alternate; stipules lanceolate, free or connate and 2-cleft, 7-11 mm; petiole 2.5-10 cm; leaf blade often orbicular or broadly ovate, sometimes ovate or elliptic-ovate, 5-15 × 3.5-13 cm, herbaceous, secondary veins ca. 3 each side of midvein, abaxial surface snowy tomentose, sometimes light green with strigose hairs on veins, or thinly white tomentose, adaxial surface slightly rough and sparsely hispid, base subtruncate, rounded, cordate, or cuneate, margin dentate from base, apex cuspidate or acuminate. Glomerules unisexual, on specialized, unisexual flowering branches in the axils of current or recently fallen leaves, these paired and much branched, usually shorter than petioles and often congested in fruit, male branches proximal or sometimes absent, female distal. Male glomerules few-flowered, 2-4 mm in diam.; female glomerules many-flowered, 2-3 mm in diam. Male flowers 4-merous, sessile; perianth lobes connate to middle, ca. 1.5 mm, pubescent. Female flowers rhomboid-ellipsoidal, 0.6-0.8 mm; stigma ca. 1 mm. Fruiting perianth rhomboid-obovoid, compressed, ca. 1 mm, strigose on shoulder, base constricted and stalklike, apex almost without neck, 2-3-toothed; achenes subovoid, ca. 0.6 mm, base stipitate. Fl. May-Aug, fr. Sep-Nov.

Forest margins, thickets, moist places along streams, roadsides, often cultivated; 200-1700 m. S Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, S Shaanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Bhutan, Cambodia, India, Indonesia, Japan, Korea, Laos, Nepal, Sikkim, Thailand, Vietnam].

This species is extremely variable, but can be distinguished easily by its alternate leaves, cymose inflorescences, and stipitate achenes. Two varieties are recognized: var. nivea is known only from cultivation or from naturalized populations; it is a stout plant with dense, long, spreading hairs, free stipules, and broadly ovate to suborbicular leaf blades with the abaxial surface densely, rarely more thinly, white or gray tomentose. Naturalized plants are often smaller with smaller, relatively narrower leaves and shorter inflorescences. Truly wild populations are very variable in stature and indumentum, but can be consistently distinguished by the appressed to assurgent hairs on the stems and leaves and the connate stipules, and are here distinguished as var. tenacissima. The plants are sometimes cultivated. Such plants with concolorous leaves have been variously named as var. concolor, var. tenacissima, var. viridula, and Boehmeria thailandica, but the diagnostic characters seem inconsistent, with many intermediate forms, even within local populations, and so all have been included here within var. tenacissima. More field work and molecular studies are needed to understand more fully this complex species.

Boehmeria nivea is cultivated widely in China, mainly in Jiangxi, but also in S Gansu, S Henan, Hubei, Hunan, S Shaanxi, and Sichuan. The history of the cultivation of this species in China can be traced back at least 3000 years. Ramie, which provides high-quality fiber, is used to make ropes, cloth, and some industrial materials. Ramie was introduced to Europe and North and South America in the early 18th century. Ramie plants are used medicinally to relieve internal fevers and treat infections of the urethra. In addition, young leaves are used as fodder for silkworms.