Lamium purpureum aka Purple Deadnettle

Lamium purpureum, or purple dead-nettle, is in the mint family. It is an annual: each plant lives for one year. It grows through winter, though some plants grow in summer. Its native range spans Macaronesia, the Mediterranean, and Europe to western Siberia. Britain and Ireland are part of its native range. People brought it to North America, Greenland, and Japan. It grows in lawns, gardens, meadows, roadsides, and disturbed ground.

Plants form low clumps or mounds. They grow fast in cool spring weather. They can reach 2.5 feet [0.76 m], but most stay shorter. Rich soil helps them grow lush; poor soil can keep them small. The main stem is smooth, with four sharp angles. Mature stems may have no leaves on their lower third. Leaves grow in pairs on opposite sides of the stem. Each pair turns from the next. The heart-shaped leaves have soft hairs and toothed or wavy edges. Sunken veins make their top sides look wrinkled. Young upper leaves have purple tones, then turn dull green. The leaves look like nettle leaves but have no stinging hairs.

Small, reddish-purple flowers form rings, or whorls, above the leaf joints. Each flower tube has a hooded upper lip and lower lips. Most plants bloom from mid-spring into late spring. This lasts about six weeks. Plants that sprout in summer may bloom in autumn. In mild weather, flowers can appear at other times, including winter. Each flower forms four nutlets. Bees visit the blooms for nectar, which they offer in winter. The long bloom season gives this weed some value for wildlife.

Grow it in full sun, though it can take light shade. It does best in moist, rich soil that drains well. It also grows in sand, loam, and heavy clay. The soil can be acid, neutral, or alkaline. North Carolina State lists it for USDA zones 4–8. Seeds can sprout when the weather stays mild, even in winter. Grow new plants from seed. It needs little care and is easy to grow.

It can seed itself and form dense patches in beds and lawns. Plants For A Future says it is easy to control. Disease and insect pests do not often harm the leaves. Young leaves and shoot tops are edible, raw or cooked. Use them in salads or stir-fries. Plants For A Future lists no known hazards. It also notes past use as medicine, including bruised leaves placed on cuts. These reports do not prove that such treatments are safe or work.