A non-native herbaceous annual plant growing to 1 m tall; it is a pioneer species and thrives on disturbed sites or roadsides. The plant looks like mint but is taller. The stems have reflexed hairs and swollen nodes. In cross section, the stem is square. The leaves are rhombic to elliptic, with coarsely to bluntly serrate edges. The flowers are multicoloured, with purple, pink, or white areas; diminutive, bilateral and snapdragon-like, and are mostly visited by bumblebees.
Typical habitat is rough ground, arable land, logging clearances and waste places. It spreads readily as its sharp calyces adhere to clothing and animal pelts