Urtica dioica aka Stinging Nettle

Urtica dioica, or stinging nettle, belongs to the nettle family. This perennial herb loses its leaves for winter. Its native range includes Europe, Asia, Africa, and western North America. It is native to Britain and Ireland too. It now grows across much of the world. It lives beside streams, in woods, and on disturbed ground.

Garden plants reach about 3.3–4.9 feet [1–1.5 metres] tall. Other sources report heights reaching 9 feet [2.7 metres]. RHS gives a spread of 8.2–13.1 feet [2.5–4 metres]. NC State lists a narrower width of 1–3 feet [0.3–0.9 metres]. Creeping roots and underground stems let colonies cover much larger areas. Upright green stems have a roughly square cross-section. Dark green leaves grow in opposite pairs along them. Each leaf has toothed edges and a sharp tip. The leaf base has a heart shape. Both leaves and stems bear hairs that can sting.

Small flowers grow where leaves join stems and at stem tips. Their shades range from cream to green or brownish green. The clusters can look like small catkins. RHS records flowering from late spring into early autumn. Wind carries the pollen between flowers. Small oval fruits, called achenes, hold the seeds. The fruits turn cream, tan, or yellow, and mature in autumn.

Nettles grow fast in rich soil with plenty of nitrogen. They favour moist ground that drains well and dislike drought. Sun suits them, though they also grow in shade. They tolerate clay, loam, sand, and chalk soils. RHS lists acid, neutral, and alkaline conditions as suitable. Hardiness ratings are USDA zones 4–10 and RHS H7. Plants need no pruning and have few pest or disease problems. Their spread is a greater concern than their health. Roots and freely shed seed can make removal hard. Nettles become invasive in some places outside their native range.

Wildlife gardens use nettles as food for butterfly caterpillars. The stems supply fibre for cloth, string, and paper. Leaves also yield dye, and the plant has traditional medicinal uses. Young leaves and shoots can serve as cooked greens. Heat or thorough drying removes the sting. Older leaves contain cystoliths that may irritate the kidneys. Wear gloves when handling fresh growth. Contact can cause burning, itching, and skin irritation. Chewing the plant can harm pets, causing mouth pain and swelling. Dogs may vomit, stumble, or develop muscle twitches. PFAF also warns about drug interactions and use during pregnancy.