Dead nettle is a downy perennial that spreads by rhizomatous stolons. Stems are square with pairs of leaves that are toothed, stalked and slightly heart shaped.
Flowers are borne in whorls in the leaf axils from March to late autumn. They are white or purple with hairy upper hoods and toothed lower lips. They provide a nectar source for long-tongued insects such as bumble bees and mason bees.