A member of the Labiatae or Dead-nettle family, this perennial reaches about 75cm in height. It has a distinctive unpleasent smell when crushed. Grows in sun or partial shade in well drained soil spreading mainly by extended rhizomes.
The velvety, dark green leaves are serrated with long stalks and oppose each other on the stem. They are heart-shaped, 5 to 15 cm long and 2 to 5 cm wide with a tapered end.
Spikes of hooded flowers appear in whorls from June to October. They vary from pink to dark purple and the lower lip has paler markings.

The underground stems are shallow and easily uprooted but any remaining parts may regrow. Does not withstand repeated close cutting.
A systemic or translocated herbicide will work, eg Gylphosate.

See also Stinging Nettle and Common Hemp-nettle which have similar leaves.