Renanthera citrina

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An interesting article on the new yellow-flowered species from the
limestone areas of northern Vietnam by an expert. With photographs.
Published : Tuesday, August 02, 2011
Reading/s : 196
Number of pages: 7
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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,.
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