Roscoea auriculata
Encyclopedia
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.
which occurs in grasslands, between 2,400 and 2,700 metres in the mountains of Tibet, Bhutan, Nepal and Sikkim.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
, to which the tuberous roots
are attached. 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. auriculata is usually 20–40 cm tall, with three to seven leaves. The blade of the leaf (the part free from the pseudostem) is 7.5–20 cm long by 2–2.5 cm wide. The leaf sheath is smooth (glabrous) and purple in colour. At the junction of the blade and sheath there are ear-shaped (auriculate) outgrowths.
In its native habitats, R. auriculata flowers between June and August. The stem (peduncle
) of the flower spike does not emerge from the leaf sheaths. Several purple or white flowers are produced. Membranous bracts, 2–2.5 cm long subtend the flowers.
Each flower has the typical structure for Roscoea
(see that article for labelled images). There is a tube-shaped outer calyx, about 3.5 cm long. Next the three petal
s (the corolla) form a tube longer than the calyx, terminating in three lobes, each about 3.5 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 white petals, about 2 cm long, upright and hooded; two central staminodes are fused at the base to form a lip or labellum, about 4.5 cm long by 3 cm wide. This is split at the end into two lobes.
The single functional stamen has a linear anther, about 1 cm long, borne on a 1 cm long filament. A short spur is formed from the connective tissue between the two capsules of the anther. After flowering, a capsule 2–3 cm in length is formed containing brown seeds.
, a German botanist, in 1904. In 1966, H. Hara reduced it to a variety of a different species, Roscoea purpurea
var. auriculata. However, more recent sources have maintained it as a separate species.
The specific epithet auriculata refers to the two ear-shaped (auriculate) outgrowths at the junctions of the leaf blades and sheaths.
.
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. auriculata falls into the Himalayan clade as would be expected from its distribution. It appears to be closely related to R. alpina
.
, it was given a position which was sunny in the morning but shaded in the afternoon; it should not be planted in full sun or in too hot a position. Deep violet-purple and white forms are in cultivation.
A form with large, richly coloured flowers is grown as Roscoea auriculata 'Floriade'.
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 eastern Himalayas, in Tibet
Tibet
Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
, Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
, Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
and Sikkim
Sikkim
Sikkim is a landlocked Indian state nestled in the Himalayan mountains...
. 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. auriculata, 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 auriculata 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 grasslands, between 2,400 and 2,700 metres in the mountains of Tibet, Bhutan, Nepal and Sikkim.
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 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...
are attached. 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. auriculata is usually 20–40 cm tall, with three to seven leaves. The blade of the leaf (the part free from the pseudostem) is 7.5–20 cm long by 2–2.5 cm wide. The leaf sheath is smooth (glabrous) and purple in colour. At the junction of the blade and sheath there are ear-shaped (auriculate) outgrowths.
In its native habitats, R. auriculata flowers between June and August. The stem (peduncle
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
) of the flower spike does not emerge from the leaf sheaths. Several purple or white flowers are produced. Membranous bracts, 2–2.5 cm long subtend the flowers.
Each flower has the typical structure for 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...
(see that article for labelled images). There is a tube-shaped outer calyx, about 3.5 cm long. 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 longer than the calyx, terminating in three lobes, each about 3.5 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 white petals, about 2 cm long, upright and hooded; two central staminodes are fused at the base to form a lip or labellum, about 4.5 cm long by 3 cm wide. This is split at the end into two lobes.
The single functional stamen has a linear anther, about 1 cm long, borne on a 1 cm long filament. A short spur is formed from the connective tissue between the two capsules of the anther. After flowering, a capsule 2–3 cm in length is formed containing brown seeds.
Taxonomy
The species was named by Karl Moritz SchumannKarl Moritz Schumann
Karl Moritz Schumann was a German botanist.Dr. Schumann was the curator of the Botanisches Museumin Berlin-Dahlem from 1880 until 1894...
, a German botanist, in 1904. In 1966, H. Hara reduced it to a variety of a different species, Roscoea purpurea
Roscoea purpurea
Roscoea purpurea is a perennial herbaceous plant occurring in the Himalayas, particularly Nepal. Most members of the ginger family , to which it belongs, are tropical, but species of Roscoea grow in much colder mountainous regions...
var. auriculata. However, more recent sources have maintained it as a separate species.
The specific epithet auriculata refers to the two ear-shaped (auriculate) outgrowths at the junctions of the leaf blades and sheaths.
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. auriculata falls into the Himalayan clade as would be expected from its distribution. It appears to be closely related to R. alpina
Roscoea alpina
Roscoea alpina is a perennial herbaceous plant native to the Himalayas, from Kashmir to Burma. Most members of the ginger family , to which it belongs, are tropical, but R. forrestii, like other species of Roscoea, grows in much colder mountainous regions...
.
Cultivation
Some Roscoea species and cultivars, including R. auriculata, 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. auriculata has been described as one of the "most commonly grown and easy species". When grown at the Royal Botanic Gardens, KewRoyal 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...
, it was given a position which was sunny in the morning but shaded in the afternoon; it should not be planted in full sun or in too hot a position. Deep violet-purple and white forms are in cultivation.
A form with large, richly coloured flowers is grown as Roscoea auriculata 'Floriade'.
For propagation, see Roscoea: Cultivation.