Datisca is a small genus of two (or sometimes three) species of large herbaceous flowering plants, placed in the family Datiscaceae within the order Cucurbitales — the same order that includes cucumbers and begonias. Plants grow as tall, robust herbs with alternate, pinnately divided leaves that superficially resemble those of hemp (Cannabis), which explains the specific epithet of the best-known species, Datisca cannabina.
One of the most distinctive biological features of the genus is its actinorhizal habit: Datisca species form symbiotic root nodules with nitrogen-fixing Frankia bacteria, capturing atmospheric nitrogen and enriching the soils they inhabit. Notably, Datisca is the only non-woody genus known to carry this adaptation, making it an outlier among actinorhizal plants, which are otherwise trees or shrubs such as alder and sea-buckthorn.
The genus contains two well-accepted species. Datisca cannabina, native to the eastern Mediterranean and western Asia (Crete, Turkey, and through to the Himalayas), reaches about 2 m in height and bears small greenish-yellow flowers from May to August. It is strictly dioecious, with male and female flowers on separate plants. The species has historically been cultivated for its ornamental foliage, used as a source of a yellow dye, and employed in traditional medicine as a laxative. The closely related Himalayan D. nepalensis is sometimes treated as a separate species and sometimes subsumed within D. cannabina. The second species, Datisca glomerata, is native to California, Nevada, and northern Mexico; it is largely dioecious, though female plants may occasionally produce bisexual flowers as well.
Etymology
The genus name Datisca is of uncertain or obscure origin; the specific epithet of the best-known species, cannabina, derives from the Latin cannabis (hemp), reflecting the plant's hemp-like pinnate foliage.
Distribution
Datisca cannabina occurs in Crete, Turkey, and extends east through the Himalayas (where the closely related D. nepalensis is sometimes recognized as a distinct species). Datisca glomerata is native to California, Nevada, and northern Mexico, typically growing in rocky stream beds and canyon washes.
Ecology
Datisca species are actinorhizal plants, forming symbiotic associations with nitrogen-fixing Frankia bacteria in root nodules. They are the only non-woody plants known to carry this adaptation, which allows them to colonize nutrient-poor soils. D. glomerata is characteristic of disturbed riparian habitats in semi-arid regions of western North America.
Cultural Uses
Datisca cannabina has been used historically to produce a yellow dye from its stems and leaves, and preparations from the plant have been employed as a laxative in traditional medicine. The species is also cultivated as an ornamental for its bold, hemp-like foliage.
