Biorepository Data Portal

Herbs , 0.7-7 dm. Stems simple, erect. Leaf blades elliptic to broadly elliptic or ovate, paired blades equal, 2-13 × 1-9 cm, margins dentate. Inflorescences crowded to lax. Flowers ca. 1 mm across. Achenes uniformly light colored or with streaks of purple, compressed, teardrop-shaped, 1.3-1.7 × 0.6-1.1 mm, smooth or purple striations sometimes raised. 2 n = 24, 26. Flowering summer-fall. Moist to wet woods, woodland margins, along streams, shaded waste places; 0-2000 m; N.B., Ont., P.E.I., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.; Asia. Typical plants have leaf blades with cuneate bases and 3-11 rounded teeth on each margin; plants with rounded leaf bases and 11-17 less rounded or acute teeth on each margin have been called Pilea pumila var. deamii (Lunell) Fernald (M. L. Fernald 1936) [ Adicea deamii Lunell, Amer. Midl. Naturalist 3: 10. 1913.]. Typical P . pumila also is found in eastern Asia, where three infraspecific taxa, P . pumila var. pumila , P . pumila var. hamaoi (Makino) C. J. Chen, and P . pumila var. obtusifolia C. J. Chen are recognized. This complex, which also includes P . pauciflora C. J. Chen, has been placed in Pilea series Pumilae C. J. Chen. Although the Asian plants are often vegetatively and florally indistinguishable from the North American plants, minor differences do occur in the achenes, especially in their markings and sculpturing when mature. Detailed studies are needed to clarify exact relationships. Native Americans used Pilea pumila medicinally to alleviate itching, to cure sinus problems, and to treat excessive hunger (D. E. Moerman 1986)

Annual herb 7 cm - 0.7 m tall Stem: erect and unbranched. Leaves: opposite, long-stalked, 2 - 13 cm long, 1 - 9 cm across, elliptic to egg-shaped with a wedge-shaped base, toothed, usually hairless. Flowers: either male or female, found on the same plant (monoecious), borne axillary in a flat-topped inflorescence of both male and female flowers, subtended by bracts, about 1 mm across. The male flowers have four tepals and four stamens, while the female flowers have three tepals and sterile stamens. Fruit: an achene, pale green and sometimes purplish streaked, 1.3 - 1.7 mm long, 0.6 - 1.1 mm across, teardrop-shaped, smooth or sometimes with the purple streaks raised. The achene is ejected when mature.

Similar species: Boehmeria cylindrica and Parietaria pensylvanica have flexible, non-stinging hairs, and Laportea canadensis and Urtica dioica both have stiff, stinging hairs and flexible, non-stinging hairs. Pilea fontana is distinguished by its black, warty achene.

Flowering: late July to early October

Habitat and ecology: Common in cool, moist, shaded areas such as rock canyons, wooded moist depressions, shaded floodplains, or under bridges.

Occurence in the Chicago region: native

Etymology: Pilea comes from the Greek word pilos, meaning cap, referring to the achene being covered by the longer sepal of some species in the genus. Pumila means dwarf.

Author: The Morton Arboretum

Annual, very smooth and pellucid, 1-5 dm; lvs long-petioled, shining, ovate, 3-12 cm, serrate or crenate-serrate, broadly cuneate to rounded at base, usually glabrous, 3-nerved from the base, the nerves narrowly winged; terminal lf-tooth elongate; cymes 5-30 mm from the middle and upper axils; cal-lobes equal or nearly so; achenes pale green, usually with slightly raised purple spots, 1.3-2 mm, 55-70% as wide as long; seed smooth. Moist, rich, shaded soil, often in colonies; Que. to Minn., s. to Fla., La., and Okla. July-Sept. (Adicea p.) Northeastern plants have the lvs sharply cuneate at base, with 11 or fewer rounded teeth on each side. Toward the s. and w. the lf-base tends to be more rounded, and the teeth sharper and more numerous; this poorly defined phase has been called var. deamii (Lunell) Fernald.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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