Most orchids prefer a marked fluctuation, from ten to fifteen degrees, between day and night time temperatures. However, similar to other houseplants, orchids won't tolerate cold weather. Keep them away from windows during extreme cold.
To provide your orchids with the variance in temperature they need, consider lowering the setting of your nighttime thermostat, depending upon the variety of orchid you're growing. Especially during the autumn and winter, manipulating your home temperature encourages your orchid to bloom as well as grow.
Although many tropical orchids grow in the treetops, some Australian cultivars grow entirely underground. Knowing the light requirements of your orchid cultivar is one of the steps to successful orchid growing. Although you may be familiar with terms like full sun, bright-filtered light, part-shade, and dense-shade, a light meter gives you a precision measurement of the light your orchids receive.
A light meter helps you to prevent problems caused by inappropriate lighting. However, if you don't have a light meter, your orchid will notify you of problems by changes in its leaves. Healthy leaves on most orchid varieties are usually grass green. An orchid with dark green, lusterless leaves needs more light. Orchids show that they're getting too much light when leaves have burn spots or feel hot to your touch.
Southern and eastern exposures usually provide the best light for orchids. When you're without a good window for an orchid, fluorescent shop lighting makes good artificial light for orchids. Although grow lights provide a better spectrum of light, cool-white shop bulbs work well for many varieties of orchid.
Always use lukewarm water when watering your orchids.
Both temperature and light also help determine when to water your orchid. Wait to water your orchid during cooler temperatures (below 60° F) or when your orchid has been in reduced light conditions for over three days.
During active growth periods, water your orchids weekly, allowing them to dry slightly in between waterings. When you do water, watch for water to drain out of the bottom of your pot. Orchids grown in small pots, porous pots, and bark mixtures may need more frequent watering.
Orchids prefer humidity between 40% and 70%. Although humidity is often low during winter months, you can easily make a humidity tray. Add a layer of pebbles to any shallow container and cover them with water. However, elevate your orchid so that the pot doesn't stand on the wet gravel. Growing orchids by a kitchen sink, in a bathroom, or other place where hot water is used also provides some of the humidity orchids need.
Unfortunately, the high humidity that orchids need is also a good incubator for bacteria and fungi. Besides natural pathogens like bacteria and fungi, smoke, aerosol sprays, and air born gases from items like plastics and even the ethylene gas apples generate may damage your orchids. Because orchids drawn oxygen and nutrition from the air, along with other care requirements an important part of growing orchids is providing them with both good air circulation and air quality.
Although orchids may need some fertilization because orchid potting mixes don't hold nutrients well, fertilize sparingly according to the needs of your orchid variety. When in doubt, less is more for your orchid.
Orchids require regular fertilization to grow and flower properly, but too much fertilizer can quickly damage plants. Water-soluble types of fertilizer specifically formulated for orchids are available at most garden centers and are easy to use. Apply soluble fertilizers monthly, according to the rates recommended on the label. Flush any accumulated fertilizer salts out of the pot once a month with plain water.
Orchids rest after flowering. When the foliage growth stops, reduce both water and fertilizer applications until new leaf production starts again.