Reproducing only by seed.
Stems erect, 40-180cm high, square, somewhat hairy along the angles, branched, frequently several stems from 1 coarsely fibrous root crown.
Opposite leaves (2 per node), lower ones long-stalked, rounded in outline, palmately cleft into usually 5 or more main lobes which are coarsely or irregularly toothed, upper leaves on shorter stalks, smaller, and only 3- or 5-cleft.
Flowers in the axils of small upper leaves; calyx tubular with 5 slender, sharp lobes, 3 pointing upwards and 2 downwards, becoming hard, sharp, and spiny at maturity; the calyx breaking off and clinging as a bur to clothing or fur; corolla pink to pale purple or whitish, upper lip conspicuously white-hairy, not lobed, lower lip 3-lobed; each flower producing 4 nutlets ("seeds") which are triangular, dark brown and hairy at the apex. Flowers from June to August.
Motherwort occurs throughout southern Ontario in yards, waste places, fence lines, and roadsides.
It is distinguished in non-flowering stages by its palmately lobed leaves (almost like maple leaves) in geometrically precise arrangement in 4 vertical planes around the square stem. Flowering and fruiting plants are distinguished by their palmately lobed leaves, clusters of pinkish flowers in leaf axils, and the calyx of each flower with 5 very sharp lobes, 3 pointing upwards and 2 downwards, these becoming spiny bur-like clusters on mature and dry stems.
A. Top of plant before flowers open. B. Mature calyx with its 5 slender, spiny-tipped lobes.
Flowers of motherwort.
Opposite leaf arrangement.
Lower leaf of motherwort.
Upper leaf of motherwort.
Bird's eye view photo of motherwort.