Heat Damage on Orchid Leaves

Light

• Orchids vary in their light requirements. Orchids that need relatively low amounts of sunlight are from the Paphiopedilum, Phalaenopsis and Oncidium families. These orchids should be exposed to at least a half-day's worth of filtered sunlight each day, whether through a sheer curtain or dappled shade. Orchids that need a bit more light are from the Cattleya, Dendrobium, and Vanda families. They need light all day long, but never direct sunlight. Place these orchids in a west or south facing window, but protect them with a sheer curtain, or move them away from the window a bit during the months of May through September.

Temperatures

• Most orchids grow best in normal indoor house temperatures, according to the University of Hawaii at Manoa website. Some of the hardiest can withstand temperatures as low as 50 degrees Fahrenheit, and as high as 90 degrees Fahrenheit. When the temperatures get that hot, however, humidity and water become absolutely vital. In normal conditions, orchids still need air that is at 40 percent humidity. Increase this to 60 percent if possible when the temperatures rise, and keep the soil moist, but not waterlogged. Often, orchids can survive periods of hot weather just fine if they are kept well-watered and are not in direct sunlight.

Symptoms

• The foliage on your orchids will indicate if they are being exposed to too much heat and sunlight. If the orchid's leaves are turning purple or reddish on the borders, it is suffering from too much heat and direct sunlight. In addition, orchids that are being exposed to too much sun will have leaves that look "bleached out" -- turning yellow or pale green. The most severe damage an orchid plant can suffer from heat is sun scald. This is indicated by white spots that turn black and eventually flake off.

Treatment and Prevention

• Sun scalding on an orchid is irreversible -- there is not much you can do about it other than to prune off the leaves, move the plant to a cooler location and hope that it recovers. If you see the leaves start to turn pale or develop red borders or spots, move the orchid to a shaded location and give it more water.