Orchids are the largest and most highly evolved family of blooming plants in the world. They come in many sizes, shapes, and colors, and they can offer some of the most spectacular blooms you'll ever find on a houseplant. While some orchids can be tricky to grow, many others will flourish on a windowsill. All you need for successful orchid growing in your home is an understanding of the plant's native environment.
Although orchids are native to the tropics, they are not found down in the steamy jungle lowlands, living instead at elevations from 3,000 to 6,000 feet. At this level, they have come to like a drop in their night temperature of about 10°, and they'll flower best if you can provide this.
Because they come from regions with high air moisture, most orchids are happiest with humidity levels of 40% to 60%. Since most of our households have humidity levels between ten and twenty percent, it's clear that we must raise the moisture level around orchids to keep them their happiest. This can be accomplished several ways: you can mist the plants daily; you can run a humidifier near them; or, simplest, you can place your orchids on a pebble tray. This is a container at least 5" high and larger than the pot, in which at least 1 1/2" of gravel has been placed. Add an inch of water to the container and maintain the water at that level (but never touching the bottom of the pot in which the orchid is planted). As it evaporates, the water will increase the humidity immediately surrounding the orchids.
Most orchids like to dry out somewhat between watering. Generally, an orchid with thick, fleshy leaves will need less water than one with thin, delicate leaves. Always water orchids in the morning to allow the foliage to dry thoroughly before night.
Orchids in the wild are fertilized only by tiny bits of organic material that wash over their roots, so they are generally not heavy feeders. We suggest an orchid fertilizer or a half-strength solution of a 20-20-20 formulation during growing season, fed twice a month.
Orchids send out clear signals about their light condition. If the foliage is reddish or purple at the edges, then the plants are getting as much light as they can tolerate. Too much light can also bleach out the chlorophyll, turning the leaves yellowish or pale green. If the foliage is a dark, grass green, and the plants just refuses to flower, then they are not receiving enough light. You'll know your light is just about right if your orchid has clear light to medium green foliage and blooms regularly. Generally, orchids are happy with bright indirect light (no blazing sunshine, please).
Occasionally, orchids can develop problems with mealy bugs, scales, and aphids. Most of these problems can simply be washed off the plant outdoors. You can even spray rubbing alcohol on the plant if you prefer not to use harsher chemicals. If your orchids "summer" outdoors, you can avoid problems with slugs and snails by not setting the pots directly on the ground.
Generally, orchids only need repotting when they outgrow their containers or when the potting medium begins to break down (perhaps every 2-3 years). Remember that orchids demand impeccable drainage. This explains why they are often potted in ﬁr bark, osmunda fiber, volcanic rock, or charcoal.
Cattleya gaskelliana: By QuazDelaCruz (Own work) [CC0], via Wikimedia Commons