Leonurus japonicus Seeds | Motherwort
LATIN NAME: Leonurus japonicus
COMMON NAME: Motherwort
Plant Profile
Leonurus japonicus is a tall, square-stemmed herb of the mint family, with leaves cut into narrow lobes and whorls of small pink-purple flowers packed around the stem at each node. It grows to about a metre, often on waste ground and along field edges, and it seeds itself freely. The whole plant has a faint, rank smell when bruised, which is not the mint scent its family suggests.
The species is native to eastern Asia and is now widespread as a weed in disturbed ground. It is an annual or biennial, flowering in summer and dying after seed set, and a single plant can produce thousands of small, three-sided seeds. In Chinese pharmacy it is known as yi mu cao, and the dried aerial parts are sold in bundles.
Science & Biotechnology
The plant contains alkaloids, chiefly leonurine and stachydrine, together with diterpenes and flavonoids. Leonurine has been studied for its effects on uterine muscle and on platelet aggregation, and it is the compound most often cited in pharmacological work on the species. The essential oil is minor compared with the alkaloids, and the smell comes from it rather than from the active compounds.
The genus is a member of the Lamiaceae, and it shares the family’s square stems and opposite leaves, but it lacks the aromatic oil glands that make mint useful in cooking. The seeds are dispersed mechanically: the calyx hardens around the seed, and the whole unit attaches to fur and to clothing, which is how the plant spreads along paths and roadsides.
Uses & Benefits
In Chinese medicine the aerial parts are used for menstrual disorders, for postpartum bleeding and for swelling, usually in a decoction with other herbs. It is a strong uterine stimulant and is not used during pregnancy. In Western herbal practice a related species, Leonurus cardiaca, is used for palpitations and for anxiety, and the two are often confused in the trade.
The plant is also used as a fodder for livestock in some districts, and the seed is eaten in times of scarcity. It is grown in herb gardens for the flowers and for the bees, and it is one of the plants that appears without being invited on disturbed ground.
Growing from Seed
Seed germinates readily and needs light. Surface-sow in spring or autumn on a fine seedbed, press it in, and keep it moist; seedlings appear in two to three weeks. The plant self-sows freely, so one flowering is usually enough to establish it.
The plant grows on almost any soil, but it prefers a sunny site with moderate moisture. It is hardy to about minus twenty and needs no care. Cut the flowering stems for drying just as the lower flowers open, and hang them in a dark, airy place, since the alkaloids degrade in strong light.
Our Take
A plain-looking herb with a serious medicinal record, best grown at the back of a border where its self-sowing will not become a nuisance.
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