ORCHID SPECIES CULTURE
Charles and Margaret Baker

Rhynchostylis gigantea (Lindley) Ridley

AKA: Saccolabium giganteum Lindley, Vanda densiflora Lindley, Saccolabium
harrisonianum Hooker, Saccolabium albolineatum Teijsmann and Binnendijk,
Vanda densiflora var. petotiana Rchb. f., Vanda hainanensis Rolfe, Anota
densiflora (Lindley) Schlechter, Anota harrisoniana (Hooker) Schlechter,
Anota hainanensis (Rolfe) Schlechter, Rhynchostylis gigantea subvar.
petotiana (Rchb. f.) Guillaum, Rhynchostylis densiflora (Lindley) L. O.
Williams, Anota gigantea (Lindley) Fukuyama, Rhynchostylis gigantea var.
harrisoniana (Hooker) Holttum. 

ORIGIN/HABITAT: Burma, Thailand, Malaya, Laos, Cambodia, Vietnam, China,
Borneo, and Indonesia. In Burma, plants grow near Rangoon and Toung-ngoo
as well as elsewhere in the north, but they are not found in the
Tenasserim Provinces in the south. In Thailand, plants are found
throughout most of the mainland from the eastern areas around Prachinburi
northward through Nakorn Sawan and Loei to near Chiengmai in the north,
where plants have been collected at 870 ft. (265 m), they are also found
in the Kanburi district in the southwest, just north of peninsular
Thailand. In Malaya, plants are known to grow in Singapore and surrounding
islands. In Laos, plants are found on the Vientiane Plain and in the
Bolovens region. In Cambodia, Rhynchostylis gigantea has been found on Mt.
Camchay. In Vietnam, it is known from near Ho Chi Minh City (Saigon) and
near Quangtri. In China, the type specimen for Vanda hainanensis was found
on Hainan Island. In Indonesia, plants grow on Anambas Island and other
islands in the China Sea. In Borneo, plants are found in the lowlands at
numerous locations. 

CLIMATE: Station #48455, Bangkok, Thailand, Lat. 13.7N, Long. 100.5E, at
53 ft. (16 m). The record high temperature is 114F (46C), and the record
low is 50F (10C).

N/HEMISPHERE    JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC
F AVG MAX        89   91   93   95   93   91   90   90   89   88   88   88
F AVG MIN        68   73   76   78   77   77   76   76   76   75   73   69
DIURNAL RANGE    21   18   17   17   16   14   14   14   13   13   15   19
RAIN/INCHES     0.5  0.9  1.5  3.6  6.2  6.0  6.6  6.8 11.8  9.2  2.3  0.4
HUMIDITY/%       72   74   74   75   78   79   80   81   83   83   80   74
BLOOM SEASON    ***  ***   **    *    *    *    *         *    *        **
DAYS CLR @ 7AM    4    2    1    0    0    0    0    0    0    1    2    3
DAYS CLR @ 1PM    9    5    4    2    0    0    0    0    0    2    2    6
RAIN/MM          13   23   38   91  157  152  168  173  300  234   58   10
C AVG MAX      31.7 32.8 33.9 35.0 33.9 32.8 32.2 32.2 31.7 31.1 31.1 31.1
C AVG MIN      20.0 22.8 24.4 25.6 25.0 25.0 24.4 24.4 24.4 23.9 22.8 20.6
DIURNAL RANGE  11.7 10.0  9.5  9.4  8.9  7.8  7.8  7.8  7.3  7.2  8.3 10.5
S/HEMISPHERE    JUL  AUG  SEP  OCT  NOV  DEC  JAN  FEB  MAR  APR  MAY  JUN

Cultural Recommendations: 

LIGHT:  3000-4000 fc. Light should be bright but indirect light may be
best, and full mid-day sun might sunburn the plant. Strong air movement
should be provided at all times. 

TEMPERATURES: Summer days average 90-91F (32-33C), and nights average
76-77F (24-25C), with a diurnal range of 14F (8C). The warmest
temperatures of the year occur in spring during the relatively clear
weather at the end of the dry season. Spring days average 93-95F (34-35C),
and nights average 76-78F (24-26C), with a diurnal range of 16-17F
(9-10C). 

HUMIDITY: Near 80% most of the year, dropping to 70-75% in winter and
early spring. 

WATER: Rainfall in the habitat varies from heavy to very heavy starting in
late spring and lasting into autumn. Averages then decrease rapidly into
the dry season that lasts for 3-4 months in winter and early spring.
Cultivated plants should be watered heavily while actively growing, but
aeration around the roots must be excellent, allowing the roots to dry
rapidly after watering. For plants grown in pots or baskets, the medium
must never become water logged or soggy. 

FERTILIZER: 1/4-1/2 recommended strength, applied weekly when plants are
actively growing. Many growers prefer to use a balanced fertilizer
throughout the year, but others use a high-nitrogen fertilizer from spring
to midsummer, then switch to a high-phosphate formula in late summer and
autumn.

REST PERIOD: Winter days average 88-91F (31-33C), and nights average
68-73F (20-23C), with a diurnal range of 18-21F (10-12C). Although these
temperatures are fairly common throughout the range of distribution,
plants from northern Thailand and Burma commonly experience winter minimum
temperatures 8-10F (4-6C) cooler than indicated, so cultivated plants
should adapt to winter night temperatures as low as 60F (16C) to as warm
as 70F (21C). Rainfall in the habitat is low for 3-4 months in winter and
early spring. Humidity remains relatively high, however, so some moisture
is available from heavy dew and late-night mist. Cultivated plants need
less water in winter, and they should become rather dry between waterings.
If winter humidity in the growing area is high, an occasional
early-morning mistings between infrequent light waterings should provide
sufficient moisture in most growing areas. If humidity in the growing area
is low, however, the early-morning mistings should be increased. Plants
should never dry out completely. Fertilizer should be reduced or
eliminated until heavier watering is resumed in spring. 

GROWING MEDIA: Rhynchostylis are reported to be singularly intolerant of
stale conditions around the roots but neither do they like being disturbed
for repotting. They are, therefore, best grown in a manner that allows the
numerous aerial roots to hang free. Growers may place them in wooden
baskets without any supplemental potting medium or else mount them on
tree-fern or cork slabs with no padding around the roots. If grown in this
manner, however, humidity must be high and plants should be watered at
least once daily in summer and plants may need several waterings a day
when conditions are hot and dry. Because many growers have trouble keeping
their plants adequately moist, they are often grown in pots or baskets
using a very open, fast draining medium, which allows the roots to dry
rapidly after watering. Using a mixture of medium- to large-sized fir bark
with an equal amount of medium- to large-sized hardwood charcoal produces
good results. Charcoal may be used alone. Rhynchostylis do not respond
well when disturbed, but if plants are grown in a container filled with a
bark mix, they should be repotted every year because any break-down of the
medium will cause a rapid decline of the root system. Because the
inflorescence emerges at the base of the stem, plants should be placed
high in the pot. Plants become reestablished faster with less stress if
they are mounted or repotted just as new root growth is starting. See also
the note under Flowers.

MISCELLANEOUS NOTES: The bloom season shown in the climate table is based
on cultivation records. In the habitat, plants normally bloom in winter. 

Plant and Flower Information:

PLANT SIZE AND TYPE: A fairly large, 24 in. (61 cm) monopodial epiphyte. 

PSEUDOBULB/STEM: Up to 4 in. (10 cm) long. The stem is robust but very
short. It is densely leafy and produces numerous very stout roots. Stems
frequently branch, however, and older, well-grown plants may be have many
stems. 

LEAVES: To 12 in. (30 cm) long by 2-3 in. (5.0-7.5 cm) wide. The dark
green, strap-shaped leaves are very thick and leathery, unequally bilobed
at the tip, and frequently marked with prominent, pale green, longitudinal
stripes. 

INFLORESCENCE: To 15 in. (38 cm) long. The pendulous, densely flowered
spike emerges from the stem at the base of the leaves. 

FLOWERS: Up to 50 on each inflorescence. Aa medium-sized plant may produce
3-4 inflorescences, and a large, well-grown plant may produce even more.
Kamemoto and Sagarik (1975) reported that in Bangkok a large,
many-branched specimen has produced as many as 30 flower spikes.
Individual flowers are 1.0-1.5 in. (2.5-3.8 cm) across. The waxy blossoms
are highly fragrant and last about 2 weeks. Flowers usually are white,
with red-violet, amethyst-purple, or magenta spotting, and they often have
a well-defined apical blotch of the same color. The lip is red-violet,
amethyst-purple, or magenta which usually fades to a whitish color at the
base and toward the middle. Some all white clones have been found, and
very occasionally, plants with all red flowers are found.
Sepals and petals are elliptic-oblong, spreading, more or less sharply
pointed, and often rather wavy. Sepals are about 0.6 in. (1.5 cm) long by
0.3 in. (0.8 cm) wide. Petals are about 0.6 in (1.4 cm) long by 0.2 in.
(0.5 cm) wide and are widest near the apex. The almost oblong lip is
3-lobed at the apex with small, rounded lateral lobes and a much smaller
but also rounded midlobe. The blade of the lip is 0.5 in. (1.2 cm) long by
0.3 in. (0.7 cm) wide, fleshy, and slightly hairy. It points straight
forward, is nearly oblong, and widens somewhat from the base. The disc
consists of 2 hairy ridges that descend into the spur. The short spur,
which is 0.2-0.3 in. (0.6-0.7 cm) long, is inflated but somewhat laterally
compressed, backward-pointing, and bluntly tipped. 
Red-flowered clones have been crossed with other red clones by growers in
Thailand. About 80% of the progeny produced by this breeding were red,
which has resulted in red clones being more readily available. Kamemoto
and Sagarik (1975) reported that the red color of these flowers is
affected by temperatures preceding the flowering season. When autumn
temperatures are warmer than normal, the red coloring does not develop
fully and some of the normally red-flowered plants will produce flowers
with large white blotches.

HYBRIDIZING NOTES: The chromosome count is 2n = 38 as reported by Kamemoto
and Sagarik (1975). They further stated that compared to plants from other
regions, those from near Chiengmai in the north have heavier stems;
shorter, thicker, and darker green leaves; and larger flowers, even though
the chromosome count is the same as plants from other regions. 

REFERENCES:

Bechtel, H., P. Cribb, and E. Launert. 1980. Manual of cultivated orchid
species. MIT Press, Cambridge, Mass.

Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211
Beckwith Road, Richmond, B.C., Canada V6X 1V7.

Hawkes, A. [1965] 1987. Encyclopaedia of cultivated orchids. Faber and
Faber, London. 

Kamemoto, H., and R. Sagarik. 1975. Beautiful Thai orchid species. Orchid
Society of Thailand, Aksornsampan Press, Bangkok, Thailand. 

Pridgeon, A. ed. 1992. The illustrated encyclopedia of orchids. Timber
Press, Portland, OR. 

Seidenfaden, G. 1988. Orchid genera in Thailand XIV. Fifty-nine vandoid
genera. Opera Botanica 95, Copenhagen, Denmark.

Seidenfaden, G. 1992. The orchids of Indochina. Opera Botanica 114,
Copenhagen, Denmark.

Seidenfaden, G., and J. J. Wood. 1992. The orchids of peninsular Malaysia
and Singapore. Published in association with The Royal Botanic Gardens,
Kew and Botanic Gardens, Singapore. Olsen & Olsen, Helstedsvej 10, DK-3480
Fredensborg, Denmark. 

Wood, J. J. and P. Cribb. 1994. A checklist of the orchids of Borneo.
Royal Botanic Gardens, Kew. 

PHOTOS/DRAWINGS:

Bechtel, H., P. Cribb, and E. Launert. 1980. Manual of cultivated orchid
species. MIT Press, Cambridge, Mass. (Color photo)

Kamemoto, H., and R. Sagarik. 1975. Beautiful Thai orchid species. Orchid
Society of Thailand, Aksornsampan Press, Bangkok, Thailand. (Color photos
of normal, white, and red color forms)

Pridgeon, A. ed. 1992. The illustrated encyclopedia of orchids. Timber
Press, Portland, OR. (Color photo)

Seidenfaden, G. 1988. Orchid genera in Thailand XIV. Fifty-nine vandoid
genera. Opera Botanica 95, Copenhagen, Denmark. (Color photo and drawing)


Copyright 1999, Charles O. Baker and Margaret L. Baker
Sheet version 64817872

.........................................................................
Please remember that this sheet is for your use only, and though it was
provided free of charge, it may not be reproduced or retransmitted in
any way without permission.
.........................................................................

__________________________________________________________________________
 "Orchid Species Culture" Charles & Margaret Baker, Portland, Oregon USA

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