L.
Description
Urena lobata is a pantropical subshrub of remarkably wide distribution, with GBIF recording over 31000 occurrences spanning the Americas, Africa, Asia and Australasia, including the United States, Brazil, China, Australia, India, Indonesia, Madagascar, the Philippines and many other countries. A vigorous colonist of open, disturbed and seasonally moist ground, it grows along roadsides, in waste places, fallow fields, forest margins and grassland, mostly at low to middle elevations. The plant photographed at Zhemgang in southern Bhutan at about 1200 m, in October, occupies the warm subtropical foothill habitat where it is a common weed of cleared and cultivated land.
The plant is an erect, woody-based perennial herb or subshrub clothed throughout in stellate, often stinging-rough hairs. The leaves are alternate, variable, the lower ones rounded and shallowly three- to five-lobed or angled, the upper narrower, with toothed margins and conspicuous nectaries on the principal veins beneath. The flowers are solitary or clustered in the leaf axils, with an epicalyx of five bracteoles, five free pink to rose petals, and the stamens united into a staminal column typical of the Malvaceae. The fruit is a depressed schizocarp splitting into five indehiscent mericarps, each densely covered in glochidiate (hooked) spines that cling to fur and clothing, ensuring epizoochorous dispersal.
Urena lobata is economically significant as a bast-fibre plant, cultivated and gathered as "Congo jute" or "aramina", and the hooked fruits make it both an effective long-distance disperser and an aggressive weed in many warm regions, where it is sometimes regarded as invasive. Its enormous global range and tolerance of disturbance place it well outside any conservation concern. The species exemplifies a successful pantropical weed whose burr-like fruits have carried it, often with human aid, across the tropics and subtropics of both hemispheres.
Author: L. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Flora of Tropical East Africa (Malvaceae), Borssum Waalkes revision of Malesian Malvaceae