Although a few of the Roscoea species were taken into cultivation quite a while ago, on the Canadian land they are just starting to be promoted as hardy gingers for the gardens. Usually they are offered by specialty nurseries like Lost Horizons Nursery, but I am looking forward to see more of them becoming available in the future years. The genus Roscoea was named by James E. Smith in honour of his friend William Roscoe, the founder of the first botanical garden in Liverpool, who had a particular interest in gingers (Fam. Zingiberaceae). “Most Roscoeas species have at one time or another been mixed up with at least one other” to quote the expert opinion given by T.M.E. Branney in his book: Hardy Gingers including Hedychium, Roscoea and Zingiber –RHS.
The genus belongs to Fam. Zingiberaceae, and all the species are characterized by a pseudostem- a stem formed by the tightly wrapped leaves, fleshy roots, and flowers having a particular morphology that resembles somewhat an orchid. For a more detailed description, Wikipedia has a very good stub on it. They are native to eastern Asia and molecular phylogenetic analysis placed species into two distinctive clades: a Himalayan and a Chinese one.
One of the most widely cultivated species is Roscoea purpurea, which was the first species to be described from specimens collected in Nepal by Francis Buchanan and it represents the type species for the genus. The size and colouration of the flowers, stems and foliage vary widely, according with the wide range of its natural habitats.The most common flower colours are lavender or purple-lilac, but forms with white, pink and red flower have also been discovered. Two showy varieties of Roscoea purpurea are also flowering at this time:
R. purpurea ‘Cinnamon Stick’ which grows to 24″ tall with thick, purple pseudostems – as its name suggests, and big flowers with the upper petal white and the lateral ones lavender.
R. purpurea ‘Spice Island’ has the same lavender flowers but with the upper petal purple, the back of the leaves purple and it remains a bit lower at 18-20” tall.
All Roscoea species are considered hardy to zone 6, but so far they did OK in our almost zone 5 location with winter mulching in various locations from sun to part-shade. Considering their fleshy roots, a moist soil with very good drainage is essential. Although they are usually cultivated and recommended as woodland plants, the use of some of the smaller species in alpine and scree gardens is much closer to the natural environments in which most species are found growing: exposed, steep meadows and alpine grasslands. However, as practice has shown, most species are tolerant of a wide range of garden conditions.