- Foliage armed with stinging hairs
- Main, leafy, square stem
- Short-stalked, opposite leaves with coarse teeth
- Inconspicuous, greenish flowers in drooping clusters at leaf joints
- Forms large colonies in moist, rich soils
- Square stems with fine, stinging hairs
- Opposite pairs of leaves with stinging hairs
- Greenish or brownish flowers with 4–5 sepals and no petals
- Flowers in clusters from the leaf joints
Rhizomatous perennial 0.5–2 m tall (sometimes up to 3 m).
Stems and undersides of leaves have fine, stinging bristles/hairs that cause stinging and occasionally blistering when touched. Young plants often have a reddish-purple tinge when they emerge. Plant has one main, leafy stem that is square in cross section. Short-stalked leaves, 7–15 cm long, in opposite pairs with prominent scales (stipules) at the base of leaf stalks. Leaves have saw-toothed margins, are oval in shape, and taper to a point.
Greenish, stalkless flowers, 1–2 mm long, are tinged with pink or red and grow in dense, drooping clusters at stem tips and upper leaf joints. Male and female flowers can be on separate plants or in separate clusters on the same plant. Flowers have 4 tiny sepals and no petals. Male flowers have 4 pollen stalks (stamens).
Fleshy, whitish, horizontally spreading rhizomes. Reproduces primarily from roots and forms large colonies.
Flattened, lens-shaped, hard-coated seeds (achenes), 1–2 mm.
Moist, rich soils of meadows, open forest, stream banks, ditches, old pastures, avalanche paths, and other disturbed areas at low to subalpine elevations. Thrives in soils with high organic matter.
The stinging hairs secrete acid into the skin when their brittle tips are broken upon touching. A wash of stinging nettle tea or common mullein tea (Verbascum thapsus) will often alleviate the stinging. Young leaves and stems are edible when cooked like spinach. Stinging properties disappear with cooking. The leaves have high nutritive value (iron, calcium, and vitamins A, C, and D) when eaten or drunk as a tea. Older plants, during or after flowering, contain silica crystals that irritate the kidneys and should not be consumed in large quantities. Roots and leaves are used medicinally as a diuretic, to expel phlegm from the lungs and stomach, promote milk production in nursing mothers, and treat diarrhea and dysentery. A tea of the leaves can also be used to curdle milk for making cheese.
A powdered form is used to treat hay fever and prevent the onset of food allergies. The stinging leaves may be applied to skin as a counter-irritant to bring circulation and healing to arthritic areas, sores, and bruises. Some tribal groups used a strong fiber from the stems to make twine for fishnets and snares. The fiber can also be used to make paper and cloth that is more durable than linen.