Common motherwort (Leonurus cardiaca)

Synonyms: Leonurus cardiaca subsp. cardiaca, Cardiaca vulgaris, Leonurus trilobatus

Common Names: Motherwort, throw-wort, lion's ear, lion's tail, heartwort

Description:

Common motherwort (Leonurus cardiaca) is a perennial plant in the mint family, native to central Asia and southeastern Europe [1][2]. It was brought to North America long ago for use as a medicinal herb and now grows wild across much of the United States and Canada [1][2]. MISIN tracks it because it escapes gardens and forms tough, spreading clumps on roadsides, yards, and disturbed ground that are hard to remove once established [5].

Habit:

Common motherwort is an upright perennial that grows 2 to 5 feet tall on stiff, square stems [5]. Its most helpful field mark is its lower leaves: they are divided into 3 (sometimes 5) pointed lobes that spread out like the fingers of a hand, much like a small maple leaf [5]. Higher up the stem the leaves get smaller and narrower. In summer it produces dense rings of small, two-lipped pink to pale purple flowers tucked where the upper leaves meet the stem [5].

The easiest time to spot it is summer into early fall, roughly June through September, when the flower whorls and then the prickly seed heads line the upper stem [4][5]. The hardened, prickly seed clusters stay on the dried stalks into fall and winter, so the plant is recognizable long after it blooms [5]. Look for the maple-like lobed leaves and square stems in spring and early summer [5].

At-a-glance cues:

1. Stiff, square stems 2?5 feet tall (a mint-family trait) [5]
2. Lower leaves with 3?5 pointed lobes spreading like fingers, like a small maple leaf [5]
3. Dense whorls of small, two-lipped pink to pale purple flowers where the upper leaves meet the stem [5]
4. Prickly seed heads that persist on dried stalks into fall and winter [5]

Leaves:

1. Arranged in pairs (opposite) along the stem; shape changes from bottom to top [3]
2. Lower leaves divided into 3 (rarely 5) pointed lobes radiating like fingers on a hand, with coarse teeth and deep veins, like a small maple leaf [4][5]
3. Upper leaves smaller and narrower, often three-lobed or with just a few coarse teeth [3]
4. Dark green with prominent veins and a slightly hairy surface [2][3]

Stems:

1. Soft and green (herbaceous), not woody [3]
2. Distinctly square in cross-section, strongly ridged, and slightly hairy [3][5]
3. Erect and stiff, 2?5 feet tall [5]
4. Often several stems from a shallow, spreading root system [5]

Flowers:

1. Small and two-lipped, pink to pale purple [5]
2. In dense whorls of about 6?15 where the upper leaves meet the stem [5]
3. Bloom in summer into early fall, roughly June through September [4][5]
4. Each flower sits in a calyx with sharp, prickly teeth [5]

Fruit and seeds:

1. Each flower forms 4 small, triangular brown nutlets, hairy at one end [5]
2. The nutlets are held inside the hardened, prickly calyx [5]
3. The prickly seed-head clusters line the upper stem and persist into fall and winter [5]
4. These prickly heads can catch on clothing, fur, and equipment and carry seed to new spots [5]

Habitat:

Common motherwort grows on disturbed, moist, rich ground. It is common in yards, neglected gardens, meadows, fields, open woods, floodplains, riverbanks, fence rows, waste areas, and along roadsides, and it turns up often around old farmsteads and in towns [5]. It tolerates sun to part shade [5].

The plant is native to central Asia and southeastern Europe [1][2]. It was carried to North America for use as a medicinal herb and has spread to much of the United States and Canada [1][2].

Reproduction:

Common motherwort spreads mainly by seed. Its prickly, hardened seed heads catch on clothing, pet fur, and machinery and drop seed wherever they fall off, so the plant can ride in on your boots or a mower, or spread from a patch next door [5]. Some sources also report that it creeps outward by short underground stems (rhizomes), forming dense clumps [2][3].

It is a perennial, so the same roots come back ? often bigger ? each spring [5]. The plant blooms in summer and sets large numbers of seeds inside its prickly seed heads [5]. The key to control is timing: remove plants before the summer flower whorls harden into spiny seed heads, and dig out the roots so the clump cannot regrow [5].

Impact and Damage:

For homeowners, common motherwort is mostly a stubborn nuisance weed. Once it takes hold it forms tough clumps that come back every spring and are hard to dig out [5]. Its dried seed heads carry sharp, prickly points that can scratch bare hands, so wear gloves when you handle it [5]. It is not a major garden threat, but it can crowd a flower bed or fence line and reseed freely.

For natural areas, its impact is limited compared with more aggressive invaders. It tends to stay on disturbed ground ? roadsides, edges, old clearings, and floodplains ? rather than pushing into healthy, intact natural areas [5]. Where it does establish, it can form patches that crowd out other low plants on disturbed sites [5]. There is little documented economic damage, so this draft includes no dollar figures.

Similar species:

Common motherwort is fairly easy to recognize once it flowers, thanks to its square stem, its paired leaves, and its lower leaves shaped like small maple leaves [5]. The plants most likely to be confused with it are other square-stemmed mints that also have paired, toothed leaves and whorls of small flowers ? including other motherwort species in the same genus. Common motherwort stands apart by its deeply 3?5 lobed lower leaves and the prickly calyx around each flower [5]. Before it blooms, its lobed leaves can be mistaken for other weedy herbs, but the square stem and opposite (paired) leaves quickly set it apart [3].

Monitoring and rapid response:

Signs to watch for:

1. Clumps of square-stemmed plants 2?5 feet tall with maple-like, lobed lower leaves [5]
2. Dense whorls of small pink to pale purple flowers along the upper stem in summer [5]
3. Prickly, dried seed-head clusters lining the stems into fall and winter [5]

What you can do:

1. Wear gloves ? the prickly seed heads can scratch and prick bare hands [5].
2. For a few plants or small patches, dig out the whole plant, including the roots, when the soil is moist; pulling only the tops lets it grow back [5].
3. Cut or remove the flowering stems before the spiny seed heads form in summer to stop new seed [5].
4. Mow or cut clumps close to the ground each time new shoots appear to wear the plant down over the season [5].
5. Bag any plants that already carry seed heads and put them in the trash ? do not compost them [5].
6. Keep the ground covered with desirable plants and improve drainage in wet spots, since the plant favors moist, disturbed soil [5].
7. Natural area crews should target small, new patches first and dig out roots and rhizomes across a site over repeat visits [5].

When to call a professional:

1. Large or long-established clumps that keep returning despite digging and cutting.
2. Sites where repeated hand removal is not keeping the plant in check.
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. USDA NRCS Plants Database. Leonurus cardiaca L. plants.usda.gov
2. Iowa State University Extension and Outreach, Integrated Crop Management. Motherwort (Leonurus cardiaca). crops.extension.iastate.edu
3. Michigan State University Plant & Pest Diagnostics. Motherwort ? Leonurus cardiaca. canr.msu.edu
4. University of Massachusetts Amherst Extension Weed Herbarium. Leonurus cardiaca. extension.umass.edu
5. Ohio State University Extension. Motherwort (Leonurus cardiaca), Ohio Perennial & Biennial Weed Guide. weedguide.cfaes.osu.edu

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