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1. Plants tap-rooted annuals 10-80 cm tall; inflorescence in dense clusters of mixed male and female flowers; mature achenes triangular................... ..... Urtica urens 1. Plants rhizomatous perennials 100-300 cm tall; inflorescence a panicle of either male or female flowers; mature achenes egg-shaped................ .....Urtica dioica 2. Male and female flowers on different plants; leaf blades abaxially hispid, both surfaces with stinging hairs................................ssp. dioica 2. Male and female flowers mostly on the same plants; leaf blades abaxially glabrous or puberulent......................ssp. gracilis Sources: Illustrated Flora of British Columbia and Flora North America Online. |
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