Decaisnea is a small genus of flowering plants in the family Lardizabalaceae, order Ranunculales, native to eastern Asia from China west to Nepal and south to Myanmar. Depending on taxonomic opinion the genus contains one or two species: Decaisnea insignis, described from Nepal and often treated as the Himalayan representative, and Decaisnea fargesii, distinguished by some authors as the Chinese counterpart. The only cited difference between the two is fruit colour — yellow-green in D. insignis versus bluish in D. fargesii — a distinction some botanists consider too minor to warrant separate species, preferring to combine both under the older name D. insignis.
Plants in the genus are deciduous shrubs or small trees, typically 5 to 8 metres tall with trunks up to 20 cm in diameter. The leaves are pinnate and large, 60 to 90 cm long, with as many as 25 leaflets each up to 15 cm long and 10 cm broad. Flowers are borne in drooping panicles 25 to 50 cm long; each flower is 3 to 6 cm wide with greenish-yellow sepals and no petals. The genus's most distinctive feature is its fruit: a soft, pod-like follicle up to 10 cm long and 3 cm in diameter, ranging from greenish-yellow to striking blue-black, which has earned the plant its common names "dead man's fingers," "blue bean plant," and "blue sausage fruit." Inside is a transparent, glutinous, jelly-like pulp studded with roughly 40 flat black seeds about 1 cm wide. The pulp is edible — described in D. fargesii as sweet and watermelon-like with a gelatinous texture, and in D. insignis as blander and jelly-like — while the seeds are not eaten.
Decaisnea is cultivated as an ornamental for its foliage and its unusual, brightly coloured fruit, with most garden specimens derived from Chinese seed and grown under the name D. fargesii. It succeeds in cooler temperate climates in fertile, well-drained soil and tolerates temperatures down to about −15 °C (5 °F). In parts of its native range, notably among the Lepcha people of Sikkim, the fruit pulp is valued as a food. A genus name of the same spelling, Decaisnea Lindl., is unrelated — it is a synonym belonging to the orchid genus Tropidia rather than to this Lardizabalaceae genus.
Distribution
Native to eastern Asia, ranging from China west to Nepal and south to Myanmar, with the genus's one or two recognized species roughly separating a Himalayan (Nepal) population from a Chinese one.
Taxonomy Notes
The genus is treated as containing either one or two species depending on authority: Decaisnea insignis (Himalaya/Nepal) and Decaisnea fargesii (China), distinguished only by fruit colour (yellow-green vs. bluish) — a difference some botanists regard as insignificant, combining both under the older name D. insignis. Note also that "Decaisnea Lindl." is an unrelated homonym and synonym of the orchid genus Tropidia, not part of this Lardizabalaceae genus.
Cultivation
Grown as an ornamental for its foliage and decorative, often bright blue fruit; most cultivated plants derive from Chinese seed and are grown under the name D. fargesii. Succeeds in cooler temperate climates in fertile, well-drained soil and tolerates temperatures as low as −15 °C (5 °F).
Cultural Uses
The jelly-like fruit pulp is valued as food by the Lepcha people of Sikkim.
