Light Levels for Orchids

Low Light

• Low light for orchids is about 1,000 to 1,500 foot-candles. This is the amount of light they would naturally get in the lowest levels of a heavily canopied tropical forest. Orchids such as Paphiopedilum and Phalaenopsis thrive in low light and will burn and fail to flower in higher light levels. In a greenhouse, use 70- to 80-percent shade cloth. Shade cloth provides artificial shade and is rated by the percent of full sun it blocks out. At home, place low-light orchids in an east-facing window or about 2 feet away from a south-facing window. Avoid full sun at all times.

Medium Light

• Medium-light orchids such as Tolumnias and many Cattleyas need about 1,500 to 3,000 foot-candles of light. This is the amount of light an orchid would get growing midway in the canopy of a tree where the branches begin to open up a bit, and on the ground, shaded by tall grasses. In the greenhouse, use 50-percent shade cloth. At home, place medium-light orchids in the windowsill of a west window or about 1 foot away from an unshaded south window.

High Light

• High-light orchids tolerate light levels of 3,000 to 4,500 foot-candles or more. This is the amount of light that reaches the dappled shade of the uppermost canopy of a tree. High-light--loving orchids include thick-leaved Oncidiums, Vandas and some Cattleyas. In the greenhouse provide 20-percent shade. Indoors, place high-light orchids in a southern facing window, but be sure the sun does not hit them at the hottest part of the day. Very few orchids like full sun all day.

Measuring Light Levels

• Measuring light levels for orchids takes some experience, but there are some ways to help. A light meter is the best way, but light meters can be expensive. An alternative is to use the shadow cast by your hand on a sheet of white paper 1 foot away. Full sun at noon in the summer is around 10,000 foot-candles, and your hand will cast a clearly defined dark shadow. Under low light conditions, the shadow of you hand will be blurry, and it may be difficult to make out a distinct shape. Under medium light, you will have a clearly defined shadow that is slightly blurry. In high light conditions the shadow will be dark and crisp, but not as defined as under full sun.