Can Too Much Light Hurt Orchids?

Orchid Types

• Epiphytic orchids obtain water and nutrients through aerial roots in their tropical habitats. This most common orchid type typically grows in tree canopies, reaching for the sunlight. Some epiphytic orchids are climbing in habit. Rare lithophytic orchids cling to rocks in their native habitats and are not commonly cultivated. Terrestrial orchids, such as lady slipper orchids, grow at least partially in soil on shady forest floors in temperate or tropical zones.

Phalaenopsis, Epidendrum and Oncidium Orchids

• Orchid enthusiasts consider Phalaenopsis orchids the easiest for home cultivation. These low-light epiphytic orchids perform well in either the natural, bright indirect light of an east or south window, or in artificial light. A combination of natural and artificial light is optimal. Yellow-green new leaves indicate that the light exposure is correct. The light is too low if the leaves are dark-green, or if new leaves are unusually long and narrow. A light meter allows the grower to keep the exposure at the optimal levels of 1,000 to 1,500 foot candles of light. Epidendrum and Oncidium orchids thrive under conditions similar to Phalaenopsis.

Cattleya and Dendrobium Orchids

• Cattleyas and Dendrobiums are epiphytic orchids that produce nutrient storage swellings, called pseudobulbs, along their horizontal stems. They require twice the lighting exposure as Phalaenopsis orchids, though direct light is still not recommended. The indirect lighting from a south or east window along with supplemental fluorescent light promotes flowering. Allow at least 12 hours of light each day.

Terrestrial Orchids

• Terrestrial orchids thrive in soil or partial soil on forest floors, growing wild in tropical and temperate climate zones throughout the world. Pockets of humus in cliffs and trees occasionally support terrestrial orchids in the wild. Most North American native orchids are terrestrial; some occur in open meadows as well as forests. Lady slipper terrestrial orchids require shady, low-light conditions similar to Phalaenopsis orchids. Indirect window or artificial light of approximately 1,000 to 1,500 foot candles is optimal. Fluorescent tubes suspended about a foot above the leaves provide correct levels of artificial light.