A branching, soft, weedy plant with square stems, lacking a pleasant scent, blooming in early spring. Blooms February–November. Flowers are small, bright lavender with red spots, with tubular, lipped configuration typical of the mint family, in terminal clusters, subtended by sessile leaves. Except for the leaves right beneath the flower clusters, all leaves are rounded, scalloped, close to the ground, becoming more elongated farther up the stem.
Similar species: Dead nettle (L. purpureum) has a distinctive, 4-sided, pagoda-like or pyramidal leaf arrangement. The heart-shaped leaves become larger and have longer stems the lower they are on the stalk.