Ohio Perennial and Biennial Weed Guide

Family:

Mint Family (Lamiaceae)

Other Names:

common motherwort, cowthwort, lion's-ear, lion's-tail.

Origin and Distribution:

Motherwort was introduced from Eurasia, and can now be found in southern Canada and east of Rocky Mountains in North America. It is naturalized throughout Ohio. Motherwort occurs in meadows, fields, yards, neglected gardens, open woods, floodplains, riverbanks, waste places and along roadsides. The species prefers moist, rich soils.

Plant Description:

Motherwort is a stiff-stemmed perennial that can grow up to 5 feet tall. As with other mint species, it has square stems and its foliage emits a pungent odor if crushed. The pink to pale purple flowers are grouped in clusters of 6 to 15 at the axils where upper leaves attach to the stem. Sepals located directly beneath the flowers are distinctively prickly. The plant reproduces by seeds.

• Root System:

  Motherwort has a shallow but extensive root system.

• Seedlings and Shoots:

  Young leaves are puckered between the veins giving them a crinkly appearance.

• Stems:

  Stems are 2 to 5 feet tall, erect, stiff, distinctly square, and may have short hairs along the corners. Stems sometimes branched near the top. Frequently, several stems arise from a single root crown.

• Leaves:

  Leaves are opposite (2 leaves per node), between 2 to 4 inches long, dull green, and attached to the stem by way of long stalks (petioles). Lower leaves are divided into 3 (rarely 5) distinct lobes that appear to radiate out from a central point like fingers on a hand. Lobes are coarsely toothed. Compared with lower leaves, upper leaves are smaller, less deeply toothed, and have shorter petioles. Uppermost leaves are narrow with only a few teeth.

• Flowers:

  Flowers are less than 1/2 inch long, pink to pale purple, and grouped in clusters of 6 to 15 at the axils where upper leaves attach to the stem. Flowers consist of a short tube and 2 lips. The upper lip is 2-lobed, arched, and hairy while the lower lip is 3-lobed. Sepals located directly beneath the flowers have dry prickly teeth.

• Fruits and Seeds:

  Each flower produces 4 triangular brown nutlets that have hairs at one end.

Biology:

Flowering occurs July through September. Roots are tenacious and can be hard to eradicate. Control options include improving drainage and mowing close to the ground every time shoots emerge. The plant generally does not survive cultivation.

Toxicity:

Motherwort contains lemon-scented oil that causes photosensitivity if ingested, and leaves can produce contact dermatitis in people who are susceptible.

Facts and Folklore:

• The genus name 'Leonurus' means 'lion's tail' and came about because the plant or its ragged-edged leaves were thought to resemble the tip of a lion's tail.

• The species name 'cardiaca' means 'for the heart' and refers to its early medicinal use for heart ailments.

• Motherwort was used to remedy nervousness, dizziness and other disorders of women.