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This article was originally printed in 1994 in the American Orchid Society Bulletin, 63(10):1148-1155.
Charles and Margaret Baker
The genus Coelogyne is comprised of about one hundred and
forty species. Although for the most part the species are easy to
grow and produce long lasting, fragrant flowers, they have never
become really popular with growers or recieved much attention from
orchidists. While the first inclination is to refer to it as the
forgotten genus, a more accurate reference would probably be the
Coelogyne species are spread over a large region from
India, through southeast Asia, southwest China, the Philippines, and
the islands of Indonesia to as far east as New Guinea and islands of
the southern and eastern Pacific. The species that have particularly
attracted our attention are the cool growing ones from the Himalayan
region of India and southeast Asia. The climate of this part of the
world is such that species originating here are best grown using a
program of benign neglect during winter. Heating bills are,
therefore, nice and low because these plants neither need nor want
warm temperatures. In addition, their greatly reduced need for water
in winter provides growers with opportunities to be away for several
weeks without having to worry about care for their collection.
Coelogyne cristata, C. mooreana, and C, mossiae are among the largest flowered species in the genus and are the focus of this article. We will first consider the cultural requirements that are common to these species, and then take a closer look at their specific needs.
HUMIDITY: Near 85% in summer and early autumn, decreasing to 60-70% in early winter. The driest time of year is late winter and early spring, before the summer monsoon starts, but conditions in the mountain habitat are probably not as dry as indicated by the data from low elevation weather stations.
WATER: An understanding of the general weather pattern in the habitat may help in answering that frequently asked question, "How often should I water?" Throughout this part of the world, the summer monsoon brings 4-6 months of extremely heavy rainfall. This is followed by a cool, very dry winter monsoon, which also lasts for several months. Although skies are generally clear and rainfall is low in winter over most of the region, habitats in the higher mountains are often bathed in fog and mist for much of the year. Moss covers nearly everything in this moist environment. Cultivated Coelogyne from this region should be watered heavily while actively growing, with little if any drying allowed between waterings. Water should then be gradually reduced after new growths have matured in autumn and limited in winter to occasional light waterings or early morning mistings. More water should be given if the tips of the youngest leaves start to die back or if the pseudobulbs show signs of excessive shriveling. The leaves on the older pseudobulbs may naturally die back during this time, but the tips of those on the newest growths should remain green. Likewise, slight shriveling should occur on the newest pseudobulbs. Too much shriveling indicates a need for more water and no shriveling at all indicates the plant may not bloom because of too much water. Water should be gradually increased in spring after new roots begin to grow.
FERTILIZER: A balanced fertilizer mixed at 1/4-1/2 recommended strength should be applied weekly during periods of active growth. Many growers recommend using a fertilizer lower in nitrogen and higher in phosphorus during late summer and autumn to promote better blooming the next season and to allow the new growths to harden before winter. In order to prevent salt buildup, the medium should be leached every few weeks during periods of heavier fertilizer applications. This is especially important in areas with heavily mineralized water. Leaching is performed by first watering the plant normally. Then, an hour or so later, after accumulated salts have had a chance to dissolve, flush the media with water equal to about twice the volume of the pot.
GROWING MEDIA: Plants may be mounted on cork or tree-fern slabs if humidity is high and plants are watered several times a day during hot, bright weather. However, most growers find it difficult to keep mounted plants moist enough in summer. Plants are usually grown in shallow pots or baskets using an open, fast draining medium. Fine to medium sized fir bark or tree-fern fiber is often used alone or mixed with varying amounts of additives such as charcoal, perlite or chopped sphagnum moss. We have had good success using baskets made from 1/4 in. (6 mm) mesh hardware cloth lined with a layer of coconut fiber or sphagnum. Our medium includes equal parts of fine and medium sized tree-fern fiber with about 10% fine charcoal, 10% perlite or sponge rock, and 10% chopped sphagnum or Amazon orchid moss added. In our growing conditions, with strong air movement, this combination allows for a heavier hand with watering without the medium becoming soggy or drying completely between waterings. The tree-fern fiber does not break down as rapidly as fir bark, which means repotting is required less often. If the plant outgrows the basket, it can be hauled out in mass and merely placed in a larger basket without disturbing the roots. This can be an important consideration because many Coelogyne do not like to be disturbed and may sulk for 2-3 years after repotting or dividing. Some growers suggest that thinning old pseudobulbs by cutting them out may be preferable to repotting as long as the medium has not broken down too far. When repotting is necessary, be sure it is done only when a flush of new root growth is just starting. This will allow the plant to become re-established as rapidly as possible.
MISCELLANEOUS NOTES: Leaf-tip die-back may be a problem with many Coelogyne species. While normally not fatal, it does cause unsightly plants and is usually an indication of a cultural problem instead of disease. Underwatering may cause these symptoms as may excessively low humidity. In most instances, however, the culprit is probably an excess of salt buildup in the medium which may be remedied by flushing the medium as previously discussed. These same symptoms may also be caused by root rot resulting from too much water, usually with old, broken-down medium. If uncertain as to the problem, the best action is to remove the plant from its container and check the condition of the roots. If everything is in good shape, the plant may be replaced in its container none the worse for the experience. Root rot is indicated if roots are soft and brown, and the root ball will probably fall apart as it is removed from the pot or basket. If this happens, it is obviously past time to repot. Since the plant is already out of the pot, the grower is presented with a wonderful opportunity to remove the old medium, clean up and treat the diseased portion of the plant, repot it using new medium and a clean pot, and make a vow to never again wait too long to repot.
HYBRIDIZING NOTES: The entire genus has been generally ignored by hybridizers over the years. There was a small flurry of activity prior to 1920 when 7 hybrids were registered. Since that time, however, there have only been 2 or 3. In 1950, Coelogyne Mem. W. Micholitz was recorded. This is a hybrid between C. mooreana and C. lawrenceana, an intermediate to warm growing plant from Vietnam with very large brownish-white flowers. Then in the 1970s,C. mooreana was crossed with C. cristata to make C. Linda Buckley. It is difficult to believe, but these are the only Coelogyne hybrids to be registered in recent times. The genus seems to offer wonderful opportunities for breeders who would like to tread where no man has gone before. Not only are there many opportunities for new Coelogyne hybrids, but there is exciting potential for crosses made between Coelogyne species and closely allied genera such as Pleione, Pholidota, and Dendrochilum .
While the general cultural requirements previously discussed apply
to most of the species from the region, there are some specific
conditions required by each. When these are known, it us usually
relatively simple to find an appropriate niche for each species in a
cool or intermediate growing area. Therefore, following is a brief
description of the plants and flowers and a close look at habitat,
climate conditions, and specific needs ofCoelogyne cristata, C.
mooreana, and C. mossiae .
Coelogyne cristata Lindley
A small to moderately sized sympodial epiphyte or lithophyte that grows to 6-12 in. (15-30 cm) tall with 2 dark green leaves at the top of each pseudobulb. The 6-12 in. (15-30 cm) arching inflorescence is pendent to suberect and emerges from the base of mature pseudobulbs, usually before new growth starts. 5-8 long lasting, showy flowers open simultaneously on each inflorescence. They are 3-5 in. (7-13 cm) across, are sometimes fragrant, and last 4-5 weeks if kept dry and cool. All flower parts are snow-white with a crystalilne texture and have wavy margins with reflexed tips. The lip is decorated with 4-5 yellow keels and golden yellow blotches. For a time in the past, these plants were known as Cymbidium speciossimum D. Don.
ORIGIN/HABITAT: The habitat extends eastward from about 75°E Longitude in the Garhwal region of northern India, through Nepal, Sikkim, Assam, Buhtan, and into the Khasi Hills of northeastern India. C. cristata is also reported in the mountains of northern Thailand. The habitat is usually at 5250-8530 ft. (1600-2600 m) in moss-forests where plants are found on both trees and rocks, often almost fully exposed to the sun.
CLIMATE: Station #42147, Mukteswa, India, Lat. 29.5°N, Long. 79.7°E, at 7592 ft. (2314 m). Record extreme temeratures are 91°F (33°C) and 21°F (-6°C).
N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 51 54 61 69 75 75 69 69 68 65 61 55 F AVG MIN 36 38 44 52 57 59 59 58 56 50 44 39 DIURNAL RANGE 15 16 17 17 18 16 10 11 12 15 17 16 RAIN/INCHES 1.0 2.1 1.7 1.0 0.3 4.6 11.4 12.8 4.6 3.5 0.3 0.2 HUMIDITY 61 55 50 39 44 67 91 93 83 66 55 56 BLOOM SEASON ** *** *** ** * * DAYS CLR @ 11AM N/A DAYS CLR @ 5PM 17 17 15 18 18 12 1 1 6 25 26 21 RAIN/MM 25 53 43 25 8 117 290 325 117 89 8 5 C AVG MAX 10.6 12.2 16.1 20.6 23.9 23.9 20.6 20.6 20.0 18.3 16.1 12.8 C AVG MIN 2.2 3.3 6.7 11.1 13.9 15.0 15.0 14.4 13.3 10.0 6.7 3.9 DIURNAL RANGE 8.4 8.9 9.4 9.5 10.0 8.9 5.6 6.2 6.7 8.3 9.4 8.9 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN
LIGHT: 2000-3000 fc. The heavy summer cloud cover indicates that some shading is needed from spring through autumn, but light should be as high as the plant can tolerate, short of burning the leaves. Conditions in the habiat are brightest during the winter dry season when skies are clear on more than half the days each month. Strong air movement is critically important at all times, and growers report a dramatic improvement in growth if plants are placed near a fan for maximum circulation.
TEMPERATURE: Summer days average 69-75°F (21-24°C), and nights average 58-59°F (14-15°C), with a diurnal range of 10-16°F (6-9°C).
Winter days average 51-55°F (11-13°C), and nights average 36-39°F (2-4°C), with a diurnal range of 15-16°F (8-9°C). Although these plants are able to tolerate below freezing temperatures for short periods, growers should remember that if plants are subjected to very cold conditions, they are much less likely to suffer damage if they are dry at the time they are exposed. The cool, dry rest is essential for healthy growth and flowering, but it need not be quite as long or severe as indicated by the climate data. The temperatures in the climate table represent about the coolest conditions under which this species should be grown, and cultivated plants are successfully grown in conditions 10-12°F (6-7°C) warmer than indicated. In addition , water should be reduced for 2-3 months in winter, and fertilizer should be reduced or eliminated until water is increased in spring.
MISCELLANEOUS NOTES: The bloom season shown in the climate table is based on cultivation reports. In nature, plants bloom in winter and early spring. Cultivated plants have grown into clumps 5 ft. (1.5 m) across, and one specimen was reported with more than 600 blossoms. Being one of the largest flowerd species of the genus, Coelogyne cristata made somewhat of a splash in collections and the cut flower market about the turn of the century but is now grown mostly by specialized or dedicated growers. This is probably because the species has long had a reputation of being difficult to grow and flower, which is more than likely the result of growers not fully understanding or meeting its cultural needs.
HYBRIDIZING NOTES: The chromosome count is 2n = 40.
Coelogyne mooreana Sander.
A moderately sized sympodial epiphyte that grows 12-18 in. (30-45 cm) tall with 2 glossy-green, heavily textured leaves per growth. The erect inflorescence is 15-20 in. (38-50 cm) tall and emerges from between the leaves of new growths before the pseudobulbs have formed. 3-8 fragrant flowers are 3-4 in. (7-10 cm) across. They open simultaneously and are well spaced along the inflorescence. The floral segments are snow-white except for a golden-yellow blotch on the midlobe of the lip. The blossoms last in excellent condition for 4-6 weeks if they are kept cool, somewhat dry, and in low light.
ORIGIN/HABITAT: Vietnam (formerly Annam). The plants grow at 3950-4250 ft. (1200-1300 m) in the Lang Bien Mountains near Dalat, about 150 miles (240 km) northeast of Ho Chi Minh City (formerly Saigon). As with most orchid species from Vietnam, little specific habitat information is available.
CLIMATE: Station #48881, Dalat, Vietnam, Lat. 11.1°N, Long. 108.1°E, elevation 3156 ft. (960 m). Temperatures are calculated for an elevation of 4000 ft. (1219 m) resulting in probable extremes of 90°F (32°C) and 40°F (5°C).
N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 77 79 81 82 81 78 78 77 77 77 76 76 F AVG MIN 53 54 56 59 62 62 62 62 62 60 57 55 DIURNAL RANGE 24 25 25 23 19 16 16 15 15 17 19 21 RAIN/INCHES 0.2 0.9 1.6 4.6 9.1 6.1 7.7 8.2 10.1 9.7 2.7 1.3 HUMIDITY/% 68 64 65 71 78 81 82 83 84 82 76 73 BLOOM SEASON *** ** ** ** *** * ** ** ** *** *** *** DAYS CLR @ 7AM 13 13 13 9 5 3 2 2 2 5 7 10 DAYS CLR @ 1PM 8 8 8 2 0 0 0 0 0 1 3 4 RAIN/MM 5 23 41 117 231 155 196 208 257 246 69 33 C AVG MAX 25.1 26.2 27.3 27.9 27.3 25.7 25.7 25.1 25.1 25.1 24.6 24.6 C AVG MIN 11.8 12.3 13.5 15.1 16.8 16.8 16.8 16.8 16.8 15.7 14.0 12.9 DIURNAL RANGE 13.3 13.9 13.9 12.8 10.6 8.9 8.9 8.3 8.3 9.4 10.6 11.7 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN
LIGHT: 1500-2500 fc. Strong air movement is critically important at all times. The heavy summer cloud cover indicates that shading is needed from spring through autumn, but light should be as high as the plant can tolerate, short of burning the leaves. In the habitat, winter is the brightest season.
TEMPERATURE: Summer days average 77-78°F (25-26°C), and nights average 62°F (17°C), with a diurnal range of 10-14°F (6-8°C). The warmest days occur in spring, when days average 81-82°F (27-28°C). During the winter rest, days average 76-79°F (25-26°C), nights drop to 53-55°F (12-13°C), and the diurnal range increases to 24-25°F (13-14°C).
MISCELLANEOUS NOTES: It is interesting to note that since 1972 Coelogyne mooreana has not been pictured in either the American Orchid Society Bulletin or Orchid Digest. It is difficult to understand why a species with such large attractive flowers has been ignored to such an extent. This is especially true when one considers that it is also among the easiest of the genus to grow and flower, with no special cultural demands or requirements. The bloom season shown in the climate table is based on cultivation reports. In nature, plants bloom in spring or early summer.
HYBRIDIZING NOTES: Chromosome counts are not available.
Coelogyne mossiae Rolfe
These relatively small sympodial epiphytes or lithophytes are only 8-10 in. (20-25 cm) tall with 2 leaves produced from the top of each pseudobulb. The arching to pendent inflorescence is about 8 in. (20 cm) long and, in the manner of Coelogyne cristata, emerges from the base of mature pseudobulbs before new growths start. Each inflorescence carries 8-10 loosely bunched, fragrant, long lasting blossoms that open simultaneously. They are 2.0-2.5 in. (5.0-6.4 cm) across and are white with 2 yellow-brown blotches marking the midlobe of the lip.
ORIGIN/HABITAT: Southwestern India. Plants grow at 7000-8000 ft. (2130-2440 m) in the Nilgiri and Pulney Hills. In the habitat, Magnolia and Rhododendron are common. Fog and mist occur frequently almost year-round, and moss covers everything. Coelogyne mossiae grows both on moss-covered trees and on slimy, moss-covered rocks.
CLIMATE: Station #43319, Coimbatore, India, Lat. 11.0°N, Long. 77.1°E, at 1298 ft. (396 m). Temperatures are calculated for an elevation of 7000 ft. (2130 m), resulting in probable extremes of 85°F (30°C) and 34°F (1°C).
N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 67 72 76 78 75 70 68 68 70 69 66 65 F AVG MIN 46 48 51 55 55 53 52 52 52 52 50 47 DIURNAL RANGE 21 24 25 23 20 17 16 16 18 17 16 18 RAIN/INCHES 0.6 0.4 0.5 1.6 2.5 1.5 1.7 1.2 1.6 6.3 4.0 1.4 HUMIDITY/% 61 56 52 61 68 72 74 73 74 73 73 66 BLOOM SEASON ** ** * * DAYS CLR @ 5PM 16 15 19 11 10 1 1 1 3 5 9 10 RAIN/MM 15 10 13 41 64 38 43 30 41 160 102 36 C AVG MAX 19.5 22.3 24.5 25.7 24.0 21.2 20.1 20.1 21.2 20.7 19.0 18.4 C AVG MIN 7.9 9.0 10.7 12.9 12.9 11.8 11.2 11.2 11.2 11.2 10.1 8.4 DIURNAL RANGE 11.6 13.3 13.8 12.8 11.1 9.4 8.9 8.9 10.0 9.5 8.9 10.0 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN
LIGHT: 2000-3000 fc. Light in the habitat is brightest during the winter dry season when skies are clear for more than half the days each month. Strong air movement is recommended at all times.
TEMPERATURE: The warmest days of the year occur during the clear weather in late winter and early spring. In this season, days average 75-78°F (24-26°C), and nights average 51-55°F (11-13°C), with a diurnal range of 20-25°F (11-14°C). In summer, after the start of the rainy season, days average 68-70°F (20-21°C), and nights average 52-53°F (11-12°C), with a diurnal range of 16-17°F (9°C). During the winter rest period, days average 65-72°F (18-22°C), and nights average 46-48°F (8-9°C), with a diurnal range of 18-24°F (10-13°C). For cultivated plants, however, growers report that night temperatures in winter need only drop to 50-55°F (10-13°C).
MISCELLANEOUS NOTES: The bloom season shown in the climate table is based on cultivation reports.
HYBRIDIZING NOTES: Chromosome count is 2n = 54. Although C.
mossiae is attractive, lasts well, and has relatively large
flowers, it has not been used to make any registered hybrids.
Many smaller flowered species such as C. nitida and C.
corymbosa require about the same conditions as the species
discussed here. In addition, there are species with large colored
flowers and extremely fancy lips, such as C. lawrenceana and
C. speciosa, that require somewhat warmer conditions. Species
from the tropical lowlands, however, require very warm, moist
conditions year-round. Among these are the large green and black
flowered C. pandurata as well as species with large numbers of
somewhat smaller flowers on pendent inflorescences such as C.
dayana and C. massangeana. These species are all worthy of
more attention from growers and hybridizers, and none of them are
particularly difficult if given the conditions they require. Perhaps
in a future article we can take a detailed look at the requirements
for some of these other species; but in the meantime, we hope that
the information presented here will give more growers the confidence
to try the beautiful, large-flowered, white Coelogyne.
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Rentoul, J. (1982) 1989. Growing orchids. book 3. Vandas, dendrobiums and others. Timber Press, Portland, OR.
Skelsey, A. 1979. Orchids. In: Time-Life encyclopedia of gardening. Time-Life Books, Alexandria, Va.
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