Description from Flora of China
Herbs, subshrubs, or shrubs, rarely trees, very rarely climbing, stems often fibrous, sometimes succulent. sometimes armed with stinging hairs; epidermal cells of leaves, sometimes stems, perianths mostly with prominent cystoliths punctiform to linear; Leaves alternate or opposite, stipules present, rarely absent; leaf blade simple. Inflorescences cymose, paniculate, racemose, spicate, or cluster-capitate, usually formed from glomerules, sometimes crowded on common enlarged cuplike or discoid receptacle, rarely reduced into a single flower. Flowers unisexual (plants monoecious or dioecious), rarely bisexual in partial flowers; actinomorphic, very small, (1-)4- or 5-merous, rarely perianth absent in female flowers. Calyx absent. Perianth lobes imbricate or valvate. Male flowers: stamens as many as and opposite to perianth lobes, filaments inflexed in bud; anthers 2-locular, opening lengthwise, rudimentary ovary often present. Female flowers: perianth lobes free or connate, usually enlarged in fruit and persistent, occasionally absent; staminodes scarious, opposite to the perianth lobes, or absent. Ovary rudimentary in male flowers, sessile or shortly stipitate, free or adnate to the perianth; 1-locular, ovule solitary, erect from the base; style simple, or absent; stigma diverse, capitate, penicillate-capitate (brushlike), subulate, filiform, ligulate, or peltate. Fruit usually a dry achene, sometimes a fleshy drupe, often enclosed by the persistent perianth. Seed solitary, endosperm usually present; embryo straight; cotyledons ovate elliptical or orbicular.
Plants in this family have numerous uses. The stem fiber of some genera and species is of high quality and used to make cloth, fishing nets, and ropes and for some industrial materials. In central and southern China, Boehmeria nivea is widely cultivated for ramie fiber and Girardinia diversifolia subsp. triloba is widely cultivated for “red huo ma” fiber. Boiled young shoots of Girardinia, Laportea, and Urtica are eaten as vegetables. Some species are used in local Chinese medicine. Pellionia repens, Pilea cadierei, P. microphylla, and P. peperomioides, among other species, are widely cultivated as ornamentals in China and elsewhere. Some genera, such as Elatostema, Pellionia, and Pilea, occur frequently in shady, moist habitats of subtropical forests and become dominant elements of the forest floor vegetation. Plants of the first five genera belong to tribe Urticeae, which is usually characterized by the distinctive stinging hairs.
About 47 genera and 1300 species: most numerous in wet tropical regions, extending into temperate regions; 25 genera and 341 species (163 endemic, one introduced) in China.
(Authors: Chen Jiarui (陈家瑞 Chen Chia-jui) , Lin Qi (林祁)1; Ib Friis , C. Melanie Wilmot-Dear , Alex K. Monro)
Chen Jiarui, Lin Qi -- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, Beijing 100093, People’s Republic of China.
Ib Friis -- Botanical Museum and Herbarium, Gothersgade 130, DK-1123 København, Denmark.
C. Melanie Wilmot-Dear -- Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, England, United Kingdom.
Alex K. Monro -- Department of Botany, The Natural History Museum, Cromwell Road, London SW7 5BD, England, United Kingdom.
Chen Chiajui & Wang Wentsai. 1995. Urticaceae. In: Wang Wentsai & Chen Chiajui, eds., Fl. Reipubl. Popularis Sin. 23(2): 1–404.