1. Temperature: optimum temperature range varies between 15.5-26.5 0C for most of the cultivated orchids. However, depending upon temp. requirement it can be classified as

➢ Cool Orchids (10-13 0C): Cymbidium, Paphiopedilum etc.

➢ Intermediate Orchids (13-180 C): Cattleya, Laelia, Miltonia, Oncidium, Epidendrum etc.

➢ Warm Orchids (15.5-26.50 C): Vanda, Rhynchostylis, Phalaenopsis, Dendrobium etc.

2. Light: Almost all orchids require 2400-foot candle except Paphiopedilum do best in low light intensity (i.e., 800–1200-foot candle). Less light intensity required as compared to other common garden plants. Exposure to bright sunlight cause sunburn injury and is detrimental to the plants.
3. Photoperiod: Most of the orchids do not responsive to photoperiod. Eight hours light induced early flowering eg in Cattleyas with additional light, delay flowering but enhance vegetative growth.
4. Humidity: High RH (i.e. 70-80%) is generally preferred by most of the orchids at daytime. Monopodial type requires high RH than sympodial types. Flower buds of Cattleya are more susceptible to infection at higher RH.
5. Air and CO2: Mostly cultivated and many tropical orchids are aerial rooted plants in nature so they do well when exposed to a current of fresh air. Free circulation of fresh air is also necessary to maintain the uniformity of temperature.