Plant 356

Menispermum canadense L. (Menispermaceae)


Menispermum canadense is a shade-tolerant climber native to woodlands and riverbanks of eastern North America, where it extends from southern Canada to northern Florida. The moonseed is one of only a few temperate members of the Menispermaceae, a family related to the buttercups, barberries and poppies, which is primarily distributed across the world’s tropical and subtropical forested regions. Perhaps the most (in)famous genus in the family is Chondrodendron, one of the sources of curare, the arrow poison used by some native South American peoples, and whose chemical derivatives are used in modern surgery as muscle relaxants.

In the field, for much of the year, moonseed is inconspicuous; it is merely part of a green, vegetative background. Palm-sized, grape-like leaves, with the appearance of off-centre umbrellas, are arranged alternately along thin stems that grow from an underground stem (rhizome). The male and female flowers, which are found on separate plants (dioecious), are small and arranged in clusters that are frequently hidden by the leaves. However, in late summer, long clusters of blue-black fruits, hanging from female plants, become obvious against the leaves. Their appearance means moonseed may be confused with wild grapes (Vitis). Close attention reveals that the stems of moonseed twine through other plants and lack the tendrils of Vitis, which coil around supporting plants. The difference may be crucial when collecting ‘wild food’; unlike wild grapes, moonseed is toxic.

The principal toxin is an alkaloid called dauricine, named after the Asian member of the genus, Menispermum dauricum, from which it was first isolated. Some native North American peoples, such as the Cherokee, use moonseed medicinally for dermatological, gastrointestinal and gynaecological purposes. Early European colonists of North America noted the general similarity of moonseed to one of their own medicinal plants called sarsaparilla, a favourite remedy for the treatment of venereal diseases. Consequently, moonseed was used for similar purposes, becoming known as yellow sarsaparilla; yellow because of the pigment berberine (also in barberries) in its rhizome. Another of the common names of moonseed, snake grape may reflect the plant’s twining habit, the appearance of its fruit and perhaps even its toxicity.

Unlike grapes, which are berries, moonseed fruits are technically drupes; they have a structure like that of peaches, plums and cherries. The bony, crescent moon-shaped endocarp (‘seed’) gives the genus Menispermum its name (Greek: mene, crescent moon; sperma, seed), whilst moonseed is simply a translation of the generic name.

Further reading

Ortiz RDC et al. 2007. Molecular phylogeny of the moonseed family (Menispermaceae): implications for morphological diversification. American Journal of Botany 94: 1425-1438.

Kessler PJA 1993. Menispermaceae. In Kubitzki K et al. (Eds.) The families and genera of vascular plants. II. Flowering plants - Dicotyledons. Springer-Verlag.

Stephen Harris