Humidity - Because most orchids grow in climates with moist air, they do prefer humidity levels between 50% and 80% for best orchid care. Considering the average house has about 10% to 50% humidity, some adjustments will have to be made. The effect of higher humidity can be provided by misting leaves frequently, by running a small humidifier, or by setting your plants on pebble trays. A pebble tray is a container with 2" or higher sides, larger than the pot, containing 1 1/2" or more of gravel and containing 1/4" to 1" of water. The bottom of the pot rest on the rocks, but never comes in contact with the water. Along with humidity goes good air circulation. High humidity coupled with stagnant air provides a breeding ground for fungal problems. Lacking a nice, airy room, a small fan or slightly opened window will help.
Temperature - Extreme cold is not tolerated, but fall nights to 45°F-55°F will encourage flowering. Day temperatures of 75°F to 85°F are optimal. Increase water, air movement, and humidity when temperature exceeds 85°F. Seedlings like temperatures 5°F to 10°F higher. Greatly fluctuating temperatures can cause buds to drop.
Light - A general rule of thumb for determining correct light levels is to judge by the color of the leaves. A healthy orchid in proper light has foliage that is a clear light to medium green with new leaves showing a soft sheen. The plant should flower regularly. Reddish or purple edges to the leaves are an indication that the leaves are getting as much light as they can take without burning. Too much light can bleach out the chlorophyll, causing the leaves to look pale or yellowish-green. Too low light makes foliage a dark, grass green and the plant will not flower well or at all.
Bugs and Slugs - Orchids can occasionally "come down with a bug". Mealy bugs, scales, and aphids can simply be washed off (preferably outdoors). If chemical pesticides are used, malathion will control scale, mealy bugs, and aphids. Rubbing alcohol may be sprayed on plants, blooms and buds as an alternative to insecticide. Slug and snail damage can be lessened by not setting plants directly on the ground when putting orchids outside for the summer. A product containing metaldehyde may be used to kill slugs and snails. Another option is to place a shallow saucer of beer on the ground. Slugs will be attracted to it and drown, leaving your orchid leaves alone for the most part. Expect to use a fair amount of beer!
Repotting - Most orchids will need to be repotted at one time or another - either when they out grow their existing container or when the potting medium begins to break down, generally every 2 or 3 years. Because orchids like impeccable drainage, media such as fir bark, osmunda fiber, volcanic rock, and charcoal have all been used. Exactly what mixture should be used and when to repot will depend on the orchid variety, your climate, and the size and age of the plant. For detailed instructions on repotting, see item 2 under after bloom care for orchids.
