Kew Species Profiles
Roscoea is a genus of 22 species belonging to the ginger family (Zingiberaceae), and occurring in the Himalaya. Roscoeas have fleshy roots that are dormant in winter. They are hardy in many regions but have delicate, orchid-like flowers that appear in mid-summer.
Roscoea purpurea was the first Roscoea species to be described around 1806 from specimens collected in Nepal by the Scotsman Francis Buchanan, who collected and described many new plants from India and Nepal. The genus is named after William Roscoe (1753-1831), who founded Liverpool's first botanic garden in 1803 and had an interest in gingers.
Native to the Himalaya from central India (Himachal Pradesh) to Nepal and the Bhutan-Assam frontier, between 1,500-3,100 m elevation.
DescriptionRoscoea purpurea has fleshy roots. The leaves (4-8) are soft and somewhat wavy, bright green, smooth or ciliate, 14-20 cm long and held horizontally or recurved. The leaf sheaths are often purple or reddish. The bracts are narrowly ovate and mostly hidden by the upper leaves.
The flowers are purple, mauve, red or white and appear in succession from among the upper leaves from June to September. Each flower only lasts one or two days. The floral tube is 6.5-10 cm long, but hidden by the bract and upper leaf sheath. The dorsal petal is ovate, whereas the lateral petals are shorter and rounded. The lip is three-lobed. The central lobe is obovate, 2 cm wide and divided at the tip, and the lateral lobes are linear-lanceolate. Stamen filaments have white, pointed appendages.
UsesRoscoea purpurea is cultivated as an ornamental. In northern India the fleshy roots are traditionally used for making a tonic to treat malaria. In Nepal they are boiled and eaten and also used in traditional veterinary medicine.
CultivationAt Kew the Roscoea collection is repotted in late January to early February, in a moisture-retentive but well-drained compost, before the pots are plunged into sand in an outdoor frame. The pots are watered in, then only the sand is kept damp until the first signs of growth in spring. Once in full growth, they are kept well watered and shaded on hot days. Between the time the foliage dies back in autumn and repotting takes place in winter, both pots and plunge sand are kept completely dry.
Most species are propagated readily from offsets, but they are also easy to propagate from seed, although this does mean it takes longer before they reach flowering size.
This species at KewThe first Kew collection of the striking red-flowered form was made by the Kew botanist William Baker on the Oxford University Ganesh Himal expedition in 1992, and this collection is still grown at Kew.
Roscoea purpurea can be seen growing in the Rock Garden. When the plants come into flower, pots are moved from the nursery into the Davies Alpine House for display. It can also be found at Wakehurst.
Alcohol-preserved specimens of Roscoea purpurea are held in Kew's Herbarium, where they are available to researchers from around the world, by appointment. The details of some of these can be seen online in the Herbarium Catalogue.
None known.
Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592
