University of Vermont Extension
Department of Plant and Soil Science

Winter News Article


By Dr. Leonard Perry, Extension Professor
University of Vermont

If you can't get to Hawaii this winter, then why not bring Hawaii to you? Create a tropical paradise by growing orchids indoors.

Granted, care must be taken when growing orchids at home. However, they are no more difficult to grow than most other houseplants when their particular growth requirements are met. In fact, some orchids are as easy to grow as cacti.

Although there are more than 25,000 species growing in climates ranging from the arctic tundra to the tropical rain forest, the orchids most often cultivated are species from tropical climates. They are commonly grouped by cool, intermediate, and warm temperature requirements based on the plants' optimum night requirements (45 to 50 degrees F, 55 to 65 degrees F, and above 65 degrees F, respectively).

The beginning grower should consider starting with established plants which should bloom within a year. Seedlings are less expensive but may take up to five years to flower. Natural species may be grown, but the hybrids are often more vigorous and less demanding in their cultural requirements.

Light is often a factor limiting the growth of orchids. Most orchids require relatively high light intensities and should be grown in an east or south window. However, a few will grow well under low intensity fluorescent lights.

Orchids vary in their water requirements. Many tropical orchids are epiphytes, growing on the side of trees, and will not do well if their roots stay wet. Epiphytes should be grown in a very porous potting medium such as coarse fir bark, lava rock, or coarse perlite. Terrestrial types rooted in soil require a well-drained, finer textured growth medium.

Watering frequency depends on the medium in which they are potted. Most orchids cannot survive prolonged drought and should be watered often. However, some require a "dry season" of six to eight weeks during which watering is reduced but not stopped. This "dry season" must occur immediately after maturation of the current season's growth and is often necessary to initiate flowering.

Nutrients must be provided in dilute concentrations when orchids are grown on inert media. Moderate air circulation is required for best growth.

Be aware that many factors may prevent flowering in orchids. Insufficient light is the most common reason. If there is too little light, the leaves become a deep, lush green. With too much light the leaves turn yellow-green.

For proper flowering, the leaves should have only a slight yellow tint. Some orchids may not bloom if the nighttime and daytime temperatures are the same. Consistently warm temperatures are good for vegetative growth, but may suppress flower development.

A 10 to 15 degree reduction in the night temperature for two weeks in the fall or spring is needed to initiate flower development. Dry air may result in failure of flower buds to open and death of plants in extreme cases. A relative humidity of 60 percent will alleviate the problem.

Orchids are affected by many of the same pests and diseases as other houseplants. Insects such as mealybugs and aphids can be controlled with the proper insecticide. Good cultural practices and the purchase of healthy plants will reduce the chance of disease although most fungal and bacterial diseases may be controlled using commercially available fungicides and bactericides.

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