Stinging nettle leaf surface showing long sharp hairs with glandular tips (Urtica dioica), coloured scanning electron micrograph (SEM). Stinging nettle (Urtica dioica), also called the common nettle, is a herbaceous perennial flowering plant in the family Urticaceae. It is native to Europe, Asia, northern Africa, and western North America. It is the best known member of the nettle genus Urtica. The species is divided into six subspecies. These subspecies have many hollow stinging hairs called trichomes on the leaves and stems. Each stinging hair has a bulbous tip which breaks off to leave a sharp, needle-like tube that pierces the skin and injects histamine and acetylcholine. This causes severe itching and burning that may last up to 12 hours. The common nettle has a long history of use as a source of medicine, food, and fibre. Nettles are eaten as a vegetable (cooking will destroy the stinging chemicals). Magnification: x20 when shortest axis |