Roscoea purpurea

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Roscoea purpurea
Whf purple 04 adjusted cropped.jpg
In Nepal
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Zingiberales
Family: Zingiberaceae
Genus: Roscoea
Species:
R. purpurea
Binomial name
Roscoea purpurea
Sm. [1]

Roscoea purpurea is a perennial herbaceous plant occurring in the Himalayas, particularly Nepal. [1] Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but species of Roscoea grow in much colder mountainous regions. [2] It is sometimes grown as an ornamental plant in gardens. [3]

Contents

Description

Roscoea purpurea is a perennial herbaceous plant. 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. [2] R. purpurea can grow to over 50 cm tall, with wide leaves and a stout pseudostem, although the height varies. The leaf sheaths are pale green or may have a dark reddish-purple tinge. [3]

The stem (peduncle) of the flower spike is hidden by the leaf sheaths. The flowers are the largest of any species in the genus. They are usually purple to mauve in colour, although white- and red-flowered forms have been found in Nepal. [3]

Each flower has the typical structure for Roscoea (see the diagrams in that article). There is a tube-shaped outer calyx. Next the three petals (the corolla) form a tube slightly longer than the calyx, terminating in three lobes, an upright hooded central lobe and two slightly smaller side lobes. Inside the petals are structures formed from four sterile stamens (staminodes): two lateral staminodes form what appear to be small upright petals; two central staminodes are partially fused at the base to form a lip or labellum. [2]

Taxonomy

Roscoea purpurea was named by the English botanist James Edward Smith in 1806; [1] it is the type species of the genus. [3] The generic name honours Smith's friend William Roscoe, the founder of the Liverpool Botanic Garden [4] (remnants of which can now be found at Croxteth Hall). The specific epithet refers to the colour of the flowers. [4]

Evolution and phylogeny

The family Zingiberaceae 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 plates. [5]

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, their main distributions 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. purpurea falls into the Himalayan clade as would be expected from its distribution. [5]

Distribution and habitat

Roscoea purpurea is native to the Himalayas, and in particular Nepal. [1] It occurs in a range of habitats, both damp and dry. It has been found in alpine grassland, rock faces, terraced walls, clearings and woodland edges; sometimes exposed to the full sun and sometimes in the shade of other herbaceous plants, shrubs and trees. [6]

Pollination

Roscoea purpurea is pollinated by the long tongue fly ( Philoliche longirostris ), [7] which is an obligate pollinator for R. purpurea. Philoliche longirostris is the only species of long-tongued fly distributed in the Himalayas and has the longest proboscis among all members of the Tabanidae. [8] The seasonal prevalence of this fly synchronizes closely with the peak blooming period of R. purpurea. [9] [10] Pollen transfer occurs when a fly pushes against the staminal appendages that extend from the base of the stamen at the entrance of the corolla tube. This action causes the anther and the style and stigma to descend and touch the fly's back. [10]

Cultivation

Roscoea purpurea f. rubra (formerly 'Red Gurkha') (AGM) Roscoea purpurea Red Gurkha 060821.jpg
Roscoea purpurea f. rubra (formerly 'Red Gurkha') (AGM)

Jill Cowley notes that "for many years" a different species, R. auriculata , was grown in gardens under the name R. purpurea. She provides a number of distinguishing features, which include the auriculate nature of the leaves of R. auriculata, the bright purple colour of its flowers rather than the paler colours of typical R. purpurea, the relatively shorter white lateral staminodes of R. auriculata, and the latter's deflexed (bent back) labellum. [11]

R. purpurea like other Roscoea species and cultivars, is often grown in rock gardens. Plants 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. When grown at Royal Botanic Gardens, Kew, R. purpurea emerges from the ground only in June, flowering from late July to early September. It requires shade for part of the day. [3]

R. purpurea was included in a trial of Roscoea held by the Royal Horticultural Society (RHS) from 2009 to 2011. It proved hardy (rating H4, i.e. hardy anywhere in the British Isles). One form and three cultivars were given the Award of Garden Merit (AGM): [12]

A red-flowered form found in Nepal was initially named R. purpurea 'Red Gurkha'. However, plants in cultivation vary, particularly in the colour of the leaf sheaths, which may be plain green or marked with red, so that the RHS considered that a form name was more appropriate, and the AGM was given to R. purpurea f. rubra. [12] Red is a flower colour not otherwise found in the genus. [3]

For propagation, see Roscoea: Cultivation.

Related Research Articles

<i>Roscoea</i> Genus of flowering plants

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. The flowers of Roscoea have a complicated structure, in which some of the showy coloured parts are not formed by petals, but by staminodes, sterile stamens which have evolved to become like petals. Some species are grown as ornamental plants in gardens.

<i>Cautleya</i> Genus of flowering plants

Cautleya is a small genus of perennial plants of the family Zingiberaceae, found in the eastern Himalayas through to China and Vietnam. It consists of two species of high-altitude tropical and temperate plants, native to cool forest areas – an unusual habitat for members of the Zingiberaceae. They are grown as ornamental flowering plants.

<i>Roscoea auriculata</i> Species of plant

Roscoea auriculata is a perennial herbaceous plant occurring in the eastern Himalayas, in Tibet, Bhutan, Nepal and Sikkim. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. auriculata, like other species of Roscoea, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens.

<i>Roscoea humeana</i> Species of plant

Roscoea humeana is a species of flowering plant in the family Zingiberaceae. It is a perennial 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. It is also grown as an ornamental plant in gardens.

<i>Roscoea alpina</i> Species of plant

Roscoea alpina is a perennial herbaceous plant native to the Himalayas. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. alpina, like other species of Roscoea, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens.

<i>Roscoea kunmingensis</i> Species of flowering plant

Roscoea kunmingensis is a perennial herbaceous plant native to the mountains of China, being found in Yunnan. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. kunmingensis, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea capitata</i> Species of flowering plant

Roscoea capitata is a perennial herbaceous plant native to the Himalayas, being found in Nepal. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. capitata, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea forrestii</i> Species of flowering plant

Roscoea forrestii is a perennial herbaceous plant occurring in the Sichuan and Yunnan provinces of China. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. forrestii, like other species of Roscoea, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens. It was named after George Forrest (1873–1932) who discovered it in Yunnan.

<i>Roscoea tumjensis</i> Species of flowering plant

Roscoea tumjensis is a perennial herbaceous plant occurring in the Himalayas, in Nepal. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. tumjensis, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea praecox</i> Species of flowering plant

Roscoea praecox is a perennial herbaceous plant occurring in the Yunnan province of China. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. praecox, like other species of Roscoea, grows in much colder mountainous regions. It is sometimes grown as an ornamental plant in gardens.

<i>Roscoea australis</i> Species of flowering plant

Roscoea australis is a perennial herbaceous plant found in Burma, to the south of all other members of the genus. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. australis, like other species of Roscoea, grows in much colder mountainous regions.

Roscoea brandisii is a species of herbaceous flowering plant in the Zingiberaceae family. It is a perennial found in the state of Meghalaya, India. Most members of the ginger family, to which it belongs, are tropical, but R. brandisii, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea nepalensis</i> Species of flowering plant

Roscoea nepalensis is a perennial herbaceous plant found in Nepal. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. nepalensis, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea debilis</i> Species of flowering plant

Roscoea debilis is a perennial herbaceous plant found in Yunnan, China. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. debilis, like other species of Roscoea, grows in much colder mountainous regions.

<i>Roscoea schneideriana</i> Species of flowering plant

Roscoea schneideriana is a perennial herbaceous plant found in China, in Tibet, Sichuan and Yunnan. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but R. schneideriana, like other species of Roscoea, grows in much colder mountainous regions.

Roscoea ngainoi is a perennial herbaceous plant occurring in the Ukhrul district of Manipur state, India. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but like other species of Roscoea, R. ngainoi grows in much colder mountainous regions.

Roscoea ganeshensis is a perennial herbaceous plant occurring in Ganesh Himal in central Nepal. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but like other species of Roscoea, R. ganeshensis grows in much colder mountainous regions. It is used as an ornamental garden plant, requiring moisture and shade in the summer.

<i>Roscoea <span style="font-style:normal;">×</span> beesiana</i> Species of flowering plant

Roscoea × beesiana is considered to be a hybrid between R. auriculata and R. cautleyoides which occurred in cultivation. The flowers are variable: most forms have a pale cream base colour with varying amounts of purple streaking, particularly on the lip or labellum. It was given the Award of Garden Merit by the Royal Horticultural Society in 2011. It is classified as being hardy throughout the British Isles.

<i>Roscoea wardii</i> Species of flowering plant

Roscoea wardii is a perennial herbaceous plant occurring from eastern Arunachal Pradesh in India to western Yunnan in China. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but like other species of Roscoea, R. wardii grows in much colder mountainous regions.

<i>Roscoea scillifolia</i> Species of flowering plant

Roscoea scillifolia is a perennial herbaceous plant occurring in Yunnan in China. Most members of the ginger family (Zingiberaceae), to which it belongs, are tropical, but like other species of Roscoea, R. scillifolia grows in much colder mountainous regions. As of 2013, the species is only known in cultivation and may be extinct in the wild.

References

  1. 1 2 3 4 WCSP (2011), World Checklist of Selected Plant Families, The Board of Trustees of the Royal Botanic Gardens, Kew , retrieved 2011-10-11, search for "Roscoea purpurea"
  2. 1 2 3 Wu, Delin & Larsen, Kai (2000), "Roscoea", in Wu, Zhengyi; Raven, Peter H. & Hong, Deyuan (eds.), Flora of China Vol. 24, Beijing; St. Louis: Science Press; Missouri Botanical Garden, retrieved 2011-10-01
  3. 1 2 3 4 5 6 Wilford, Richard (1999), "Roscoeas for the rock garden", Quarterly Bulletin of the Alpine Garden Society, 67 (1): 93–101
  4. 1 2 Hyam, R. & Pankhurst, R.J. (1995), Plants and their names : a concise dictionary, Oxford: Oxford University Press, ISBN   978-0-19-866189-4 , p. 435
  5. 1 2 Ngamriabsakul, C.; Newman, M.F. & Cronk, Q.C.B. (2000), "Phylogeny and disjunction in Roscoea (Zingiberaceae )" (PDF), Edinburgh Journal of Botany, 57 (1): 39–61, doi:10.1017/s0960428600000032 , retrieved 2011-10-03
  6. ↑ Cowley 2007, p. 51
  7. ↑ Paudel, Babu Ram; Shrestha, Mani; Burd, Martin; Adhikari, Subodh; Sun, Yong-Shuai & Li, Qing-Jun (2016-09-01), "Coevolutionary elaboration of pollination-related traits in an alpine ginger (Roscoea purpurea) and a tabanid fly in the Nepalese Himalayas", New Phytologist, 211 (4): 1402–1411, doi: 10.1111/nph.13974 , PMID   27112321
  8. ↑ Goldblatt, P. & Manning, J.C. (2000), "The long-proboscid fly pollination system in Southern Africa.", Annals of the Missouri Botanical Garden, 87 (2): 146–170, doi:10.2307/2666158, JSTOR   2666158
  9. ↑ Sen, S.K. (1931), "Notes on the bionomics and anatomy of Corizoneura longirostris, Hardwicke", Indian Journal of Veterinary Science and Animal Husbandry, 1: 24–28
  10. 1 2 Paudel, Babu Ram; Shrestha, Mani; Dyer, Adrian G.; Zhu, Xing-Fu; Abdusalam, Aysajan & Li, Qing-Jun (2015), "Out of Africa: evidence of the obligate mutualism between long corolla tubed plant and long-tongued fly in the Himalayas", Ecology and Evolution, 5 (22): 5240–5251, doi:10.1002/ece3.1784, PMC   6102519 , PMID   30151127
  11. ↑ Cowley, E.J. (1982), "A revision of Roscoea (Zingiberaceae)", Kew Bulletin, 36 (4): 747–777, doi:10.2307/4117918, JSTOR   4117918
  12. 1 2 Wilford, Richard (2012), "Roscoea on trial", The Plantsman, New Series, 11 (2): 78–85

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