The dioica nettle grows up to 1-2m in height in the summer and dies in the winter.
It spreads by rhizomes and stolons, which like the roots are bright yellow.
The leaves, on the other hand, appear green, with a soft consistency, from 3 to 15cm long and arranged opposite on the stem; also the latter is green, erect and filiform. The leaves of the common nettle have a serrated edge and a thin tip longer than the adjacent lateral teeth.
The pungent nettle produces small and numerous greenish or brownish flowers arranged in well compact axillary inflorescences.
The leaves and stems are provided with down, with non-stinging hairs and, in most subspecies, other stinging (trichomes). These break off on physical contact and act as needles that inject various chemicals such as: acetylcholine, histamine, serotonin, moroidine, leukotrienes and possibly formic acid. The mixture causes a sensation of pain or paresthesia, from which the Species draws its common names: stinging nettle, stinging nettle, burning weed and burning stone (all translated from English: burn nettle, burn weed and burn hazel).
The taxonomy of Species belonging to the Urtica Genus is rather confusing and the older sources use a multitude of different names. However, today we recognize at least six very distinct subspecies of U. dioica, some of which previously classified as species in themselves:
U. dioica subsp. dioica (European nettle). Europe, Asia, North Africa. He has stinging hairs
U. dioica subsp. galeopsifolia (stinging nettle). Europe. It has no stinging hairs
U. dioica subsp. afghanica . South and Central Asia. Sometimes it has stinging hairs, sometimes not
U. dioica subsp. gansuensis . East Asia (China). He has stinging hairs
U. dioica subsp. gracilis (Ait.) Selander (American nettle). North America. He has stinging hairs
U. dioica subsp. holosericea (Nutt.) Thorne (nettle canuta). North America. He has stinging hairs.
Names of other species, now considered subspecies, are: U. breweri, U. californica, U. cardiophylla, U. lyalli, U. major, U. procera, U. serra, U. strigosissima, U. trachycarpa and viridis U.
