Renanthera citrina

Leonid V. Averyanov

Description

An interesting article on the new yellow-flowered species from the
limestone areas of northern Vietnam by an expert. With photographs.

Sujets

• Orchids
• Orchidaceae
• Renanthera
• Viêt Nam
• Fleur
• Jaune

Informations

• Publié par: cattleya
• Publié le: 02 août 2011
• Nombre de lectures: 146
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Renanthera citrina

‘Eichenfels’

Polkadot’,

CHM/AOS (2003) grown by Ann & Phil

Jesup; photographed by Charles M. Fitch

Renanthera citrina

A new yellow-flowered species from the

limestone areas of northern Vietnam

Text and photographs by Leonid V. Averyanov, Dr. Sci.

ONE OF THE MOST HANDSOME AND interesting orchids investigated

during the 1995 to 1996 field season in northern Vietnam is a

never-before-seen species of yellow-flowered

Renanthera

—

Ren. citrina.

Its discovery came as ancillary research to the exploration program

funded, in part, by a grant from the American Orchid Society for "Explora-

tion of Endangered Vietnamese Paphiopedilums."

Like many other rare plants discovered during our expeditions, such as

Anoectochilus calcareus, Bulbophyllum purpureifolium, Cheirostylis

bipunctata, Cheirostylis eglandulosa, Gastrochilus minutiflorus, Liparis

conopea, Liparis emarginata

and

Paphiopedilum helenae

(Averyanov,

1996a; 1996b; 1997),

Ren.

citrina

is ecologically calcium-dependent and is

undoubtedly endemic to the limestone mountains of Indochina. It was

found in the provinces of Cao Bang and Hoa Binh in northern Vietnam on and

near the tops of ancient ridges and mesas formed by karst erosion of Paleozoic

marble like limestone. The habitats for this new species are rather open

semi-deciduous broad-leaved or mixed xerophytic forests rich in orchids.

Renanthera citrina

usually

grows epiphytically near the

bases

of

old,

gnarled,

broad-leaved trees (mostly on

species of oak,

Quercus)

or

lithophytically on mossy rock

bluffs. Its habitat is open

evergreen

mountain

forests

typically along the tops of

limestone remnant ridges and

mesas at 2,620 to 3,940 feet

(800 to 1,200 m) above sea

level. In the Province of Cao

Bang,

this

rare

plant

is

associated

with

coniferous

Keteleeria davidiana

(Pinaceae)

forests that were described

briefly in previous papers

(Averyanov,

1996a,

Averyanov et al., 1996).

Flowering

of Ren. citrina

was

not observed in the wild.

However, under cultivation in Russia the species flowers over a long period

from December to February. The bright lemon yellow flowers with crimson

marks open simultaneously creating a showy display. Without any doubt,

Ren. citrina

is an exciting new orchid for horticulture with its fine individual

A close-up of the flowers of

Renanthera citrina

‘Arborview’, CHM (2003) grown by

Robert F. Florsheim; photographed by Tek Hia

flowers, decorative inflorescence and relatively miniature growth habit. In

addition to the unusual flower color, the short stature of

Ren. citrina

should

be of particular interest to plant hybridizers seeking

Renanthera

hybrids

of manageable size (Yam, 1997). Unfortunately, like so many interesting

species that are closely associated with montane vegetation on primary

limestone,

Ren. citrina

is highly endangered in nature due to the vast deg-

radation by man of indigenous endemic xerophytic forests specific to these

ancient remnant limestone ridges and mesas all over northern Vietnam.

Formal description of

Renanthera citrina

as a new species to

science is presented here:

Renanthera citrina

Aver., sp. nov.

Affinitas a specie proxima

Renanthera pulchella

Rolfe planta

nostra foliis longioribus et angustioribus, floribus majoribus aliter

Distribution of

Renanthera citrina

in northern Vietnam.

The filled rounds

indicate sites of the species that were studied.

coloratis nee non labelli forma et structura differt.

Type:

Northern Vietnam, Prov. Cao Bang, Distr. Tra Linh, Subdistr.

Quoc Toan, open dry evergreen

Keteleeria davidiana

forest on tops of

remnant limestone mountains at 2,790 to 2,950 feet (850 to

900 m) elevation near Thang Heng lake in the environs of Thang Hen and

Lung Tao villages, 22 Oct 1995. Cultivated and flowered at the Komarov

Botanical Institute 28 Dec 1996,

L. Averyanov, N. T. Hiep and D. D.

Huyen #CB-031a

(HOLOTYPE: LE). Gathered during the International

Botanical Expedition funded, in part, by the American Orchid Society

grant for "Exploration of Endangered Vietnamese Paphiopedilums."

Monopodial epiphytes or lithophytes with erect or slightly bending stems

to 20 cm long, the internodes 1 to 1.5 cm long, with several thick roots.

Leaves lanceolate or narrowly lanceolate, rigid, leathery, curved,

unequally bilobed at the apex, the lobes rounded, 9 to 14 cm long, 1 to 1.4

cm wide, sessile, articulated, the sheaths green. Inflorescences erect or

inclined, about 15 cm long, not branching, with 7 to 10 well-spaced

flowers, the floral bracts small, triangular. Flowers odorless, bright lemon

yellow with one to three purple-violet blotches on the tepals and side lobes

of the lip. Dorsal sepal lanceolate, 16 to 18 mm long, 2.5 to 3 mm wide,

the lateral sepals widening from a narrow base, with broadly wavy edges,

about 20 to 24 mm long and 6 to 8 mm wide in the middle, the extra

width being on the side towards the lip. Petals lanceolate, nearly straight

or slightly falcate, 11 to 13 by 2 mm. Sepals and petals thickened at their

apices, each with a small fleshy dorsal apical tooth (carinate). Lip

immobile, with a broad spur 2 to 2.5 mm long, the side lobes erect, broad,

bilobulate, 2 to 2.5 mm long, 3 to 3.5 mm wide, midlobe ovate, concave,

cup shaped, turned under, blunt at the apex, 2 to 2.5 mm long, 2 mm

wide, the callus of two high double keels on the disk. Column short,

stout, pale yellow, 3 mm long, 2 mm wide, the operculum (anther cap)

pale yellow suffused with muddy purple. Pollinarium with short stipe to

about 0.8 mm long, the viscidium relatively large and heart shaped,

pollinia four in two pairs, the pollinia of each pair completely divided in

unequal semi-globular free halves.

Paratype:

Northern Vietnam, Prov. Hoa Binh, Distr. Tung Khe,

primary evergreen mountain forest on vertical rock cliffs near the top of

limestone ridge at 2,460 to 2,625 feet (750 to 800 m) elevation near Mai

Chau town, lithophytes or epiphytes, 30 Apr 1995,

L. Averyanov, N. T.

Hiep and D. D. Huyen #HB-15

(LE).

Etymology:

From the Latin,

citrinus,

reflecting the lemon yellow

coloration of the flowers.

This showy new species seems to be most closely related to the only

other yellow-flowered

Renanthera,

the rare

Ren. pulchella

Rolfe, known

from a single cultivated plant originating in Myanmar (Burma).

Renanthera citrina

differs from

Ren. pulchella

by its longer and narrower

leaves, larger flowers with different markings and in the form and structure

of the lip.

The original description of

Ren. pulchella

(Rolfe, 1914) is repeated

here to alert readers to this "lost" species with equally great horticultural

potential.

"Renanthera pulchella

Rolfe; a

Ren.

imschootiana

Rolfe floribus

duplo minoribus, labelli lobo intermedio orbiculari-ovato et

colore florum differt.

Herba epiphytica, circiter 18 cm alta. Folia disticha, anguste oblonga,

apice breviter biloba, coriacea, 6.5 to 8 cm longa, 1.5-2 cm lata. Scapi

patentes. circiter 18 cm longi, parce ramosi. Bracteae ovatae, obtusae,

concavae, 3 mm longae. Pedicelli circiter 1 cm longi. Flores mediocres.

Sepalum posticum oblongo-lanceolatum, obtusum, 1.3 cm longum;

sepala lateralia spatulata; lim-bus elliptico-oblongus, subundulatus, 1.3

cm

longus,

8

mm

latus;

unguis

4

mm

longus.

Petala

subspatulato-oblonga, obtusa, 8 mm longa. Labellum trilobum, 5 mm

Opposite

Renanthera citrina.

A. Flowering plant; B. Leaf; C. Flower, front view; D. Column and

lip; E. Unfolded lip; F. Lip, side view; G. Lip, sagittal section; H. Keels on the disk of the lip; I. Column,

front view; J. Column without operculum, front view; K, L. Pollinarium, front view and view from below;

M. Pollinarium, side view.

longum; lobi laterales triangulares, obtusi, subcarnosi, 2 mm longi et

lati; lobus intermedius ovato-orbicularis, 4 mm latus, basi

prominenter quadri-dentatus. Columna lata, brevissima. Burma.

This species flowered in the establishment of MM. A. A. Peelers et Cie,

Brussels, in August 1913. A single plant appeared in an importation of

Ren. imschootiana,

Rolfe, to which it bears a general resemblance in

habit, but the flowers are only about half as large and markedly different

in structure. The color is yellow with the side lobes of the lip and upper

half of the petals crimson."

A loose translation reads:

"Renanthera pulchella

Rolfe differs from

R. imschootiana

Rolfe by

its flowers half the size, the midlobe of the lip orbicular-ovate and the

different flower color.

Epiphytic herbs about

18 cm tall.

Leaves distichous, narrowly

oblong, shortly bilobed at the apex, leathery, 6.5 to 8 cm long, 1.5 to 2

cm wide. Inflorescences spreading, about 18 cm long, few branched.

Bracts ovate, obtuse, concave, 3 mm long. Pedicels [and ovaries] about 1

cm long. Flowers medium-sized. Dorsal sepal oblong-lanceolate, obtuse,

1.3 cm long, the lateral sepals spatulate with the limbs elliptic-oblong,

obtuse, lightly undulate, 13 mm long, 8 mm wide, the clawed base 4 mm

long. Lip three-lobed, 5 mm long, the lateral lobes triangular, obtuse,

somewhat fleshy, 2 mm long and wide, the midlobe ovate-orbicular, 4 mm

wide, the base with four prominent teeth. Column wide, very short."

The only other species from Southeast Asia with somewhat similar

coloration to

Ren. citrina

is

Renantherella histrionica

(Reichenbach)

Ridley, which differs by its shorter leaves and inflorescences (both about

one third the length) and longer column (about three times the length). D

Acknowledgments

Field work for this research was made possible by a grant from the

American Orchid Society for "Exploration of Endangered Vietnamese

Paphiopedilums" and was also supported, in part, by a grant from the

National Geographic Society (#5094-93) for "Highland Flora of the South

Vietnam." I also thank Eric A. Christenson, PhD, for turning my attention

to related yellow-flowered Burmese Renantheras and his kind help with

the English text of this article.

References

Averyanov, L.V. 1996a.

Paphiopedilum helenae

(Orchidaceae), new

slipper orchid from the North Vietnam.

Bot. Journ. (St.-Petersburg)

81(9):105-110.

_. 1996b. New species of orchids (Orchidaceae)

from Vietnam.

Bot. Journ. (St.-Petersburg)

81(10):73-83.

_ . 1997. New species of orchids (Orchidaceae) from

Vietnam.

Bot. Journ. ISt.-Petersburg)

82(3):131-148.

_., N. T. Hiep, P. K. Loc and D. D. Huyen. 1996. Endangered

Vietnamese Paphiopedilums. I.

Paphiopedilum helenae. Orchids

65(10):1062-1068.

Rolfe, R. A. 1914. New orchids: Decade 42.

KewBull.

1914:210-214.

Yam, T. W. 1997. Breeding with

Renanthera. Orchids

66(2):118-127.

Leonid V. Averyanov,

Dr. Sci.,

is a Professor of Botany and Senior

Researcher at the Herbarium of the Komarov Botanical Institute.

•

He

has published numerous articles detailing his Vietnamese studies.

Komarov Botanical Institute, Prof. Popov Street 2, St. Petersburg

197376,.