- Family: Mint Family – Lamiaceae (Labiatae)
- Growing form: Perennial herb. Rootstock with subterraneous runners.
- Height: 30–100 cm (12–40 in.). Stem sometimes slightly branching, 4-edged, hairy, upper part also with glandular hairs, internodes at most slightly longer than leaves. With unpleasant fragrance.
- Flower: Corolla irregular (zygomorphic), dark purplish red, with white markings, 12–18 mm (0.48–0.72 in.) long, fused, bilabiate, long-tubed. Upper lip convex, with dense glandular hairs, shorter than lower lip; lower lip 3-lobed, central lobe larger than lateral lobes, obovate. Calyx almost regular (actinomorphic), 5-lobed, unclearly 10-veined; lobes sharp-pointed. Stamens 4, of which 2 short, 2 long. Gynoecium composed of 2 fused carpels. Inflorescence spike-like, dense, comprised of dense, axillary whorls.
- Leaves: Opposite, long-stalked. Lacking basal rosette. Blade cordately ovate, sharp-tipped, hairy, dark green, margin regularly large-toothed. Inflorescence’s subtending bracts small.
- Fruit: 4-parted schizocarp. Mericarps slightly bristly, almost glossy surface, shiny, brown.
- Habitat: Broad-leaved forests, rich mixed swamps, parks, waste ground.
- Flowering time: July–August.
Hedge woundwort is a good indicator of broad-leaf forests. It is only common in the south-western corner of Finland, but it can grow in suitable places anywhere in the southern half of the country. During World War 2 it travelled with provisions to several places in the north.
Flowering hedge woundwort is a fabulous sight, but stems that lack its purple flowers look a little like stinging nettle. An easy way to tell the difference is to touch the leaves: nettle stings, but hedge woundwort will do nothing more than leave a metallic aroma on your hands that smells like mouse urine. Hedge woundwort is sometimes known as forest nettle and pig’s nettle in Finland – the former due to its habitat and the latter probably from its unpleasant smell. Its uninviting aroma is however important to the plant as it functions as a defence against being eaten.
The bumblebees and honeybees that pollinate genus Stachys plants don’t differentiate between them, and plants glowing close to marsh woundwort (S. palustris) can create a hybrid. Their offspring inherit features of both parents and can vary a lot in appearance. In Finland there are three other Stachus species with are rare established aliens or casual aliens: handsome wood betony (Betonica officinalis, earlier Stachys officinalis), yellowish-flowered annual woundwort (S. annua) and the smallest of the bunch, field woundwort (S. arvensis).