The Coelogyne orchid genus gets a lot less attention than it deserves. (People don't even spell it right: "Ceologyne" is a common error.) The plants have beautiful, fragrant flowers, can tolerate drought and neglect, and rapidly develop into massive, impressive specimens. The best-known species come from foothills of the Himalayas, where the elevation produces cool temperatures. The largest-flowered species in the genus, Coel. cristata, is one of these cool-growing types. To grow them well, it's important to understand the seasonal changes the monsoon creates in their native habitats.
Temperature requirements vary somewhat from species to species. High-elevation plants like cool temperatures, others will do better with intermediate temperatures. Most are cool-growing; during the wet season, temperatures can be as warm as 70-75°F (21-24C), but during the dry season it should be cooler, such as in the 50's or 60's Fahrenheit (10-20C) during the day, dropping 10-15°F (6-8C) at night. Again, temperature ranges vary somewhat with species, but many can cope with short freezes.
During the winter, water minimally; you don't want leaf tips turning brown or severe shriveling of the pseudobulbs, but some shriveling is normal and they don't want to be too wet. If the humidity is appropriate, you might only have to water once every few weeks. But during the rainy season (summer-fall), they are very difficult to overwater; if you grow them mounted, water a few times per day; if growing them in pots or baskets, you still don't want them to dry out much if at all, so use a potting mix that retains a fair amount of moisture without getting soggy, such as coconut husks, fine fir bark, or tree fern fiber.
They require high humidity; 70% is a good baseline, though it should be somewhat higher (about 85%) during the wet season and can be a bit drier (maybe 60%) during the dry season.
They need high light; provide at least 2000 footcandles. 3000 footcandles is recommended, though they can often adapt to direct sunlight.
The plants will bloom during the winter dry season; they will start to grow as temperatures begin to warm up; increase watering and fertilizer when you see new roots developing. (The best time to repot your orchid will be just as it is resuming active growth.)
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