Roscoea cautleyoides
Encyclopedia
Roscoea cautleyoides is a perennial herbaceous plant
occurring in the Sichuan
and Yunnan
provinces of China. The scientific name is also spelt Roscoea cautleoides (see below). Most members of the ginger family (Zingiberaceae
), to which it belongs, are tropical, but R. cautleyoides, like other species of Roscoea
, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens.
which occurs in pine forests, low scrub, meadows, and grasslands, between 2,000 and 3,500 metres in the Sichuan
and Yunnan
provinces of China.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
, to which are attached the tuberous roots
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. cautleyoides is usually 15–40 cm tall (occasionally up to 60 cm), with three or four leaves. Each leaf has a small ligule
, extending to about 1 mm. The blade of the leaf (the part free from the pseudostem) is usually 5–15 cm long (occasionally up to 40 long) by 1.5–3 cm wide. The leaf sheath is smooth (glabrous) or hairy (pubescent), with hairs which are more-or-less bent over (appressed). The lower part of the leaf blade is similar; the upper part is scaly.
In its native habitats, R. cautleyoides flowers between May and August. The flower spike emerges somewhat from the leaf sheaths. One or more flowers open together and may be of various colours: purple, yellow, white or less often pale pink. Green bracts, 4–6 cm long, with brownish veins, subtend the flowers.
Each flower has the typical structure for Roscoea. There is a tube-shaped outer calyx, 3–6 cm long, split to the middle on one side with a two-toothed apex. Next the three petal
s (the corolla) form a tube 3–3.5 cm long, terminating in three lobes, each 2–2.5 cm long: an upright central lobe and two side lobes. Inside the petals are structures formed from four sterile stamen
s (staminodes): two lateral staminodes form what appear to be small upright petals; two central staminodes are fused at the base to form a lip or labellum, 2.5–3 cm long. This bends backwards and is split at the end into two lobes; the sides are wavy.
The single functional stamen has a linear anther, 1–1.5 cm long (including a spur formed from the connective tissue between the two capsules of the anther).
. The name was given because of the similarity of this species – particularly the yellow colour of the flowers in some forms – to the taxon Gagnepain knew either as the genus Cautlea or as Roscoea section Cautlea.
However, Cautlea Royle is an invalid name (it was not accepted by the author), and was validated as Cautleya Hook.f. (i.e. with an added "y"). The spelling of Gagnepain's name has been altered to Roscoea cautleyoides by, for example, the International Plant Names Index and the Kew World Checklist. Most of the literature still uses the original spelling.
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, being divided by the Brahmaputra River
as it flows south at the end of the Himalayan mountain chain. It has been suggested that the genus may have originated in this area and then spread westwards along the Himalayas and eastwards into the mountains of China and its southern neighbours. R. cautleyoides falls into the Chinese clade as would be expected from its distribution. It is closely related to R. humeana
, R. praecox
and R. wardii.
at the Royal Botanic Gardens, Kew
.
A self-sown yellow seedling with wider leaves and a shorter flower stem (peduncle) than the typical species has been named Roscoea cautleyoides 'Kew Beauty'.
For propagation, see Roscoea: Cultivation.
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
occurring in the Sichuan
Sichuan
' , known formerly in the West by its postal map spellings of Szechwan or Szechuan is a province in Southwest China with its capital in Chengdu...
and Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
provinces of China. The scientific name is also spelt Roscoea cautleoides (see below). Most members of the ginger family (Zingiberaceae
Zingiberaceae
Zingiberaceae, or the Ginger family, is a family of flowering plants consisting of aromatic perennial herbs with creeping horizontal or tuberous rhizomes, comprising ca. 52 genera and more than 1300 species, distributed throughout tropical Africa, Asia, and the Americas.Many species are important...
), to which it belongs, are tropical, but R. cautleyoides, like other species of Roscoea
Roscoea
Roscoea is a genus of perennial plants of the family Zingiberaceae . Most members of the family are tropical, whereas Roscoea species are native to mountainous regions of the Himalayas, China and its southern neighbours. Roscoea flowers superficially resemble orchids, although they are not related...
, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens.
Description
Roscoea cautleyoides is a perennial herbaceous plantHerbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
which occurs in pine forests, low scrub, meadows, and grasslands, between 2,000 and 3,500 metres in the Sichuan
Sichuan
' , known formerly in the West by its postal map spellings of Szechwan or Szechuan is a province in Southwest China with its capital in Chengdu...
and Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
provinces of China.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
, to which are attached the tuberous roots
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. cautleyoides is usually 15–40 cm tall (occasionally up to 60 cm), with three or four leaves. Each leaf has a small ligule
Ligule
A ligule — is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges or a strap-shaped corolla, such as that of a ray floret in plants in the daisy family....
, extending to about 1 mm. The blade of the leaf (the part free from the pseudostem) is usually 5–15 cm long (occasionally up to 40 long) by 1.5–3 cm wide. The leaf sheath is smooth (glabrous) or hairy (pubescent), with hairs which are more-or-less bent over (appressed). The lower part of the leaf blade is similar; the upper part is scaly.
In its native habitats, R. cautleyoides flowers between May and August. The flower spike emerges somewhat from the leaf sheaths. One or more flowers open together and may be of various colours: purple, yellow, white or less often pale pink. Green bracts, 4–6 cm long, with brownish veins, subtend the flowers.
Each flower has the typical structure for Roscoea. There is a tube-shaped outer calyx, 3–6 cm long, split to the middle on one side with a two-toothed apex. Next the three petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
s (the corolla) form a tube 3–3.5 cm long, terminating in three lobes, each 2–2.5 cm long: an upright central lobe and two side lobes. Inside the petals are structures formed from four sterile stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s (staminodes): two lateral staminodes form what appear to be small upright petals; two central staminodes are fused at the base to form a lip or labellum, 2.5–3 cm long. This bends backwards and is split at the end into two lobes; the sides are wavy.
The single functional stamen has a linear anther, 1–1.5 cm long (including a spur formed from the connective tissue between the two capsules of the anther).
Taxonomy
The specific epithet was originally spelt cautleoides when the species was named in 1901 by the French botanist François GagnepainFrançois Gagnepain
François Gagnepain was a French botanist. The standard botanical author abbreviation Gagnep. is applied to plants described by Gagnepain.-References:...
. The name was given because of the similarity of this species – particularly the yellow colour of the flowers in some forms – to the taxon Gagnepain knew either as the genus Cautlea or as Roscoea section Cautlea.
However, Cautlea Royle is an invalid name (it was not accepted by the author), and was validated as Cautleya Hook.f. (i.e. with an added "y"). The spelling of Gagnepain's name has been altered to Roscoea cautleyoides by, for example, the International Plant Names Index and the Kew World Checklist. Most of the literature still uses the original spelling.
Evolution and phylogeny
The Zingiberaceae family is mainly tropical in distribution. The unusual mountainous distribution of Roscoea may have evolved relatively recently and be a response to the uplift taking place in the region in the last 50 million years or so due to the collision of the Indian and Asian tectonic platesPlate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, being divided by the Brahmaputra River
Brahmaputra River
The Brahmaputra , also called Tsangpo-Brahmaputra, is a trans-boundary river and one of the major rivers of Asia. It is the only Indian river that is attributed the masculine gender and thus referred to as a in Indo-Aryan languages and languages with Indo-Aryan influence...
as it flows south at the end of the Himalayan mountain chain. It has been suggested that the genus may have originated in this area and then spread westwards along the Himalayas and eastwards into the mountains of China and its southern neighbours. R. cautleyoides falls into the Chinese clade as would be expected from its distribution. It is closely related to R. humeana
Roscoea humeana
Roscoea humeana is a perennial herbaceous plant occurring in the Sichuan and Yunnan provinces of China. Most members of the ginger family , to which it belongs, are tropical, but R. humeana, like other species of Roscoea, grows in much colder mountainous regions...
, R. praecox
Roscoea praecox
Roscoea praecox is a perennial herbaceous plant occurring in the Yunnan province of China. Most members of the ginger family , to which it belongs, are tropical, but R. praecox, like other species of Roscoea, grows in much colder mountainous regions...
and R. wardii.
Cultivation
Some Roscoea species and cultivars, including R. cautleyoides, are grown in rock gardens. They generally require a relatively sunny position with moisture-retaining but well-drained soil. As they do not appear above ground until late spring or even early summer, they escape frost damage in regions where subzero temperatures occur. R. cautleyoides has been described as one of the "more commonly grown species" and as a robust plant that can cope with sunnier conditions and drier soil than other species of Roscoea. In cultivation, the various colour forms were noted as flowering at different times, yellow forms usually flowering before purple ones, which could start flowering as late as June in EnglandEngland
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
at the Royal Botanic Gardens, Kew
Royal Botanic Gardens, Kew
The Royal Botanic Gardens, Kew, usually referred to as Kew Gardens, is 121 hectares of gardens and botanical glasshouses between Richmond and Kew in southwest London, England. "The Royal Botanic Gardens, Kew" and the brand name "Kew" are also used as umbrella terms for the institution that runs...
.
A self-sown yellow seedling with wider leaves and a shorter flower stem (peduncle) than the typical species has been named Roscoea cautleyoides 'Kew Beauty'.
For propagation, see Roscoea: Cultivation.