Wedd. ex. Blume
Description
Pilea umbrosa is a shade-loving herb of moist montane forests across the Himalaya and into south-east Asia, recorded from Nepal, India, China, Pakistan, Bhutan and Vietnam. The roughly 307 georeferenced collections trace the temperate forest belt from the western Himalaya eastward. As its epithet (umbrosa, "of shady places") implies, it occupies damp, humus-rich, deeply shaded sites: forest floors, rock crevices, mossy banks and the margins of streams beneath broadleaved and mixed canopy. The photographed material from Garhwal at Simkarok at 2700 m in September is characteristic of its upper-temperate habitat and its late-monsoon fruiting period.
It is a succulent, often fleshy perennial herb with semi-translucent, somewhat brittle stems that may root at the lower nodes. The opposite leaves are markedly anisophyllous, the two of a pair unequal in size, ovate to elliptic, with a toothed (serrate to crenate) margin and a characteristic triple primary venation; linear cystoliths are visible on the surface, a diagnostic feature of the genus. Stipules are present at the nodes. As in most Urticaceae the inflorescences are small, axillary cymes of inconspicuous, unisexual, greenish flowers, the male flowers with reflexed tepals and explosively dehiscent stamens that fling pollen at maturity. The fruit is a minute, compressed achene.
Pilea is one of the largest genera of Urticaceae, predominantly tropical and subtropical, and unusually for the family it lacks stinging hairs, making it harmless to handle. The explosive stamen mechanism enabling wind dispersal of pollen is a hallmark of the family. P. umbrosa is a widespread, locally abundant understorey element with no conservation concern, valued ecologically as ground cover that stabilises soil on shaded forest slopes.
Author: Wedd. ex. Blume · Sources: POWO (Kew), GBIF, Flora of China Vol. 5, Flora of Bhutan Vol. 1, Flora of Pakistan, Friis's Revision of Asian Urticaceae