Ontario Weeds: Motherwort

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
5. Stems and Roots
6. Flowers and Fruit
7. Habitat
8. Similar Species
9. Related Links

Name: Motherwort, Leonurus cardiaca L.,

Other Names: agripaume cardiaque, agripaume, herbe piquante

Family: Mint Family (Labiatae)

General Description: Perennial, reproducing only by seed.

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Photos and Pictures

Motherwort. A. Top of plant before flowers open.

B. Mature calyx with its 5 slender, spiny-tipped lobes.

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Stems & Roots: Stems erect, 40-180cm (16-70in.) high, square, somewhat hairy along the angles, branched, frequently several stems from 1 coarsely fibrous root crown; leaves opposite (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 & Fruit: 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

Habitat: Motherwort occurs throughout southern Ontario in yards, waste places, fence lines, and roadsides.

Similar Species: 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.

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Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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