This is an erect biennial herb which reaches half a meter in height. It grows from a small basal rosette and bolts a leafy, erect stem which may branch. The triangular leaves are arranged oppositely on the stem and the erect inflorescences emerge from the stem and grow parallel to it, sometimes tangling with the foliage. Each inflorescence may contain many flowers. The petite flower is pinkish-lavender and about a centimeter across, flat-faced with yellow anthers. The fruit is a cylindrical capsule.
It flowers from June until September.
