- Written also: White Deadnettle
- Family: Mint Family – Lamiaceae (Labiatae)
- Growing form: Perennial herb. Rootstock slender, with runners.
- Height: 20–80 cm (8–32 in.). Stem ascending, unbranched, 4-edged, soft-haired along edges, also with glandular hairs.
- Flower: Corolla irregular (zygomorphic), white, with greenish spots, 20–25 mm (0.8–1 in.) long, fused, bilabiate, long-tubed, turning upwards. Upper lip convex; lower lip 3-lobed, central lobe obcordate, lateral lobes very small, tooth-like. Calyx almost regular (actinomorphic), 5-suoninen, 5-lobed, lobes roughly same length as calyx-tube. Stamens 4, of which 2 long and 2 short. Gynoecium composed of 2 fused carpels. Inflorescence composed of dense, spike-like, axillary whorls.
- Leaves: Opposite (decussate), stalked. Leaf-blade cordately ovate, net-veined, both sides hairy, margin large-toothed. Subtending bracts like stem leaves.
- Fruit: 4-parted schizocarp. Mericarps bristly.
- Habitat: Gardens, yards, meadows, hedgerows, banks, roadsides, wasteland, around inhabited areas.
- Flowering time: May–September(–October).
White dead-nettle thrives beside walls, on banks and elsewhere in everyday places. Its native habitat is the mountains of eastern Europe and western Asia. The species has spread with people a long time ago across Europe and southern parts of Finland mixed in with soil, manure, hay or seed mixes. They remain viable for a very long time – they have successfully germinated even after a millennium. The seeds are spread in the wild by ants, but it is a slow way to cover large distances. White dead-nettle has perhaps been spread deliberately as a tincture of the flowers has been used to treat many complaints. Its habitats in Finland do not correspond to cultivation even though, apart from its medicinal uses, the plant is also nutritious and ornamental.
White dead-nettle often grows on fertile and nitrogenous places beside stinging nettle, and plants that are not in flower can be mistaken for it with their serrated leaves. It is possible for bolder people to differentiate between them before they flower by feeling them, however, as white dead-nettle lacks its relative’s characteristic sting, having only normal bristly hairs. Usually the plants are easy to tell apart by appearance, however, because white dead-nettle blooms for many months, and its white labiate flowers differ from nettle’s small, modest flowers like chalk and cheese. White dead-nettle’s closely-situated whorls probably look as attractive to pollinators as one large flower would. Only insects with a long proboscis are able to reach the nectar way down at the bottom of the calyx-tube. They are directed to the right place by a whorl of hair, which simultaneously keeps small insects, which are useless to the plant from the point of view of pollination, at bay.
Dead-nettles have clearly net-veined leaves, and thus differ from genus Galeopsis, whose leaf-blades are feather-veined. The structures of the flowers in the different genera also differ because the lateral lobes on the lower lip of dead-nettles’ corollas are small, merged with the central lobe, or altogether absent. On genus Galeopsis the lower lip of the corolla is clearly three-lobed. Dead-nettles’ hair is soft, while on Galeopsis plants it is bristly.