Lighting
Lighting requirements vary depending on the orchid genus and the season. Plants may be moved outdoors in summer, but must always be protected from the blazing sun. Toward late August, they can be given some afternoon sunlight, which is less strong at that time.
As a general rule, Paphiopedilums and Phalaenopsis require moderately bright light and tolerate direct morning sun (east-facing window). In fall, to encourage blooming, they can be given brighter light by moving them near a west-facing window or closer to the fluorescent tubes if they are grown under artificial lighting.
Cattleyas, Cymbidiums and Vandas require brighter light and as much direct sunlight as possible (south- or west-facing window).
Temperature
Temperature plays an important role in orchid growing. There are optimal temperature conditions for each species.
For several genera, flowering is initiated when the plant is subjected to daytime and nighttime temperature fluctuations of 5 to 10ºC until the flower spike appears.
Growing requirements for the main types of cultivated orchids
| Genera | Watering | Temperature oC | ||
|---|---|---|---|---|
| Daytime | Nighttime | Nighttime (to induce flowering) | ||
| Paphiopedilum and Phalaenopsis | Allow to dry out to halfway down the pot between waterings. | 25 | 21 | 15 |
| Cattleya | Allow to dry out completely between waterings. | 21 | 17 | 14 |
| Cymbidium (cold) | Allow to dry out completely between waterings. | 18 | 12 | 10 |
| Cymbidium (temperate) | Allow to dry out completely between waterings. | 21 | 15 | 13 |
| Vanda | Water frequently. Allow to dry out completely between waterings. | 30 | 19 | - |
Paphiopedilums and Phalaenopsis require cool temperatures to encourage them to bloom. Nighttime temperatures must be around 15°C, normally between mid-August and late October. Once the flower stalk appears at the base of the plant, nighttime temperatures should be returned to normal, about 21°C.
Cattleyas usually require nighttime temperatures of 14°C before they will bloom.
Cymbidiums need nighttime temperatures of 10 to 13°C, depending on whether they are native to cold or temperate regions. In our climate, Cymbidiums do best if grown outside in summer in a slightly shady spot. These plants must be brought in before the first frost, however.
Finally, Vandas, native to moist tropical Asia, need stable conditions (hot, moist and bright sunlight) year-round. They will not bloom until they have reached maturity. The important thing is to encourage their vegetative growth with proper feeding.