These prized plants prefer filtered light, fluctuating temperatures, and not too much water by Alex Vasiljev Fine Gardening issue 82 Orchids, such as this Phalaenopsis hybrid, often produce abundant, long-lasting blooms. I got my first orchid plant at age 12, when I was growing up in the Ukraine. An orchid’s ability to root and grow entirely above the ground fascinated me. I soon acquired a collection of orchids that I grew indoors, and my interest eventually turned into a profession. With their unusual growth habits and enigmatic blooms, orchids have intrigued humans for thousands of years. However, most of what we know about orchid culture has been accumulated over the last 200 years or so.Many of the orchids brought to Europe by plant hunters in the early 18th century were epiphytes. Also known as air plants, epiphytes grow on other plants without connecting to the ground or harming their hosts. European growers, however, kept them in hot, humid, unventilated houses, which proved devastating for the orchids. The legend that orchids were difficult to grow began in that era, and it took almost 100 years for growers to develop successful methods for tending them.Now we know that many orchids are as easy to grow as African violets. The easiest to grow indoors are epiphytic— the same orchids considered so stubborn and uncooperative by early British orchid growers.Here, I will focus on growing orchids indoors—specifically those that thrive best under average conditions in a home environment. The keys to success are knowing an orchid’s needs, choosing an orchid based on the conditions you can provide, then giving it the right care. Orchids vary in their temperature preferences Ruffly-flowered Cattleya hybrids, often referred to as corsage orchids, are among the easiest orchids to grow indoors.Photo/Illustration: Alex Vasiljev Temperature affects an orchid’s overall growth and especially its bloom habits. The most critical time for orchids is during the winter, when many of them are preparing to bloom. Orchids are classified into three types based on their winter temperature needs: cool-, intermediate-, and warm-growing.Cool-growing orchids enjoy night temperatures in winter around 50°F and daytime temperatures not exceeding 70°. Intermediate-growing orchids prefer minimum winter-night temperature around 60° and daytime temperatures from 70° to 85°. Most orchids best suited for growing indoors are in the intermediate group (see sidebar). Night temperatures for warm-growing orchids should not be lower than 65°, and daytime winter temperatures can range from 75° to 85°. During the summer, intermediate- and warm-growing orchids can stand temperatures up to 85° or 90° as long as they have good air circulation. Cool-growing orchids prefer to stay cool in the summer.A fluctuation of 10 to 20 degrees between day and night temperatures is essential for all orchids and triggers them to produce flowers. This difference is most important for cool- and intermediate-growing orchids because of the conditions they are used to in the wild. In the winter, it’s possible to achieve this fluctuation by lowering your home’s thermostat or by moving an orchid to a cooler spot, like a porch or a garage, at night.Most orchids flourish under bright, indirect light. Full eastern or western exposure or indirect southern exposure usually provides enough light. However, as with temperature, specific orchids may require a certain light intensity. When buying an orchid, check the label for its light preference, then observe how much light your orchid actually receives.Symptoms of excessive light are sun burn, yellowish foliage, and a plant that looks weak and dehydrated. On the other hand, if you bought an orchid in bloom and it did not rebloom the following year, even though the foliage looks green and full, consider giving it more light. Also make sure the temperature range is correct. Repotting an orchid Orchids need to be repotted when one or more of the following occurs: the orchid is top heavy, a new orchid shoot is growing outside the container, the potting mix has deteriorated, or the orchid needs dividing. Step 1: Remove the orchid from its pot, gently separating any roots that are attached to the pot. Step 2: Loosen the old potting mix from the roots. Step 3: Remove yellow leaves and dead parts of the roots (areas that are dark and soft rather than light and firm). Step 4: Choose a container that's just slightly larger than the one being replaced. Spread the roots evenly within it. Step 5: Add fresh, porous potting mix (a packaged orchid mix or a custom blend), filling the spaces among the roots. Step 6: Gently pack the potting mix, making sure the plant roots are held firmly within the pot. Step 7: Position the plant so that it is centered and the potting mix reaches or slightly covers the uppre roots. Step 8: Water the plant thorougly and let it drain. Staking tip: The weight of gangly stems can make an orchid unsteady in its container. Metal pins like the one shown here are designed to help lock orchids within their pots. The pin clamps onto the side of the pot and holds the stems in position. It takes only a few minutes to repot an orchid, and this maintenance is essential to keep the plant thriving. Too much water can be as deadly as too little Watering is the aspect of orchid growing that can be the trickiest. Most epiphytic orchids should be grown in a loose potting mix. To be sure the orchid gets enough water, drench the mix until water runs out the bottom. Then allow the potting mix to dry out before watering the orchid again. The top layer will dry more quickly than the soil at the bottom and can make you think the orchid needs more water, but don’t be fooled.A simple way to test when an orchid needs water is to compare its weight before and after watering. Make sure the plant is completely dry before testing, then remember how it feels when you lift it. By learning the difference, you can determine how much moisture is left in the container. Experienced orchid growers advise that if you are not sure whether or not to water your orchid, wait a day.Also keep in mind that orchids need less water during their resting period, when they are not blooming or producing new growth. With the appearance of new roots and shoots, an orchid can be watered more often.Usually, resting orchids will need water once a week. When they are actively growing, I water them twice or more per week. However this is not a rule to follow precisely; you must use your own judgment. The need for water will also depend on the temperature, the container size, and the potting mix. Shriveled new stems and wilted leaves are indicators that an orchid is staying dry for too long. Too much water will eventually cause rot within the root system, leaving a plant dehydrated.Most orchids also welcome a moderate level of humidity (50 percent or higher). To achieve this, you can mist them frequently with water or use a humidifier in your home. During the growing period, fertilizing orchids once or twice a month with a reduced-strength fertilizer will promote healthy growth and strong blooms. My favorite formula is a 20-20-20 solution.Many orchid growers I’ve met have a specific soil mix they swear by. In my experience, it doesn’t matter what kind of components and how much of them you use when potting up an orchid. It’s only important that the mix be airy, drain well, and decompose slowly. Whether you mix your own or buy a prepared mix, it will work as long as those criteria are met. The numerous options include bark, sphagnum moss, tree fern fiber, and peat moss.Container size, however, is an important factor, because orchids like to be root-bound. Their roots often spread outside the container, right into the air. This does not necessarily mean the plant needs a bigger pot. See the sidebar above to help you decide when to repot. The new container should be just big enough to accommodate the root system and provide room for growth for the next year or two. The choice of clay or plastic pot is up to you.Dividing is not necessary every time you repot. I like to let an orchid grow into a larger specimen that produces multiple flowers. Limited growing space can be one reason for dividing, as well as the desire to have more than one plant, or to trade with friends. To grow quickly into a healthy blooming plant, each division should have no less than three developed stems, also known as pseudobulbs. In many orchids, you will find old, bloomed-out pseudobulbs. You should cut these off only if they’re dried and yellow; if they are still green, leave them in place. Keep an eye out for pests and disease Proper care, including good air circulation, usually keeps orchids free of problems. Nonetheless, it can be heartbreaking to find that an orchid is being tortured by pests or exhausted by disease. Early detection is a key to keeping orchids healthy. The earlier you notice a problem, the easier it will be to fix.First, I isolate a problem plant from its neighbors. If pests like scale, aphids, or mealy bugs are visible, I remove them manually with a soft brush. If a pest does get out of hand, I may resort to using a pesticide. After the treatment, I keep the plant in isolation for two to four more weeks, monitoring it regularly.Appearance of fungal or bacterial diseases on orchids can be an indication of cultural problems. The first step is to identify the disease. The next step is to evaluate growing techniques and adjust them if needed. For example, fungal disease can be the result of poor air circulation. With some bacterial diseases it is necessary to reduce watering. Sometimes a change in culture will be enough to fix the problem. If not, turn to a more aggressive treatment. Consult your local extension agent or garden center for help in choosing an appropriate fungicide or bactericide.In the summer months, orchids welcome fresh air. Of course, outdoor conditions should be similar to those you have provided for your plants indoors. When blooming time comes, it is fine to display your treasure out of the growing area, in a place of honor. The plant will not suffer if it gets less light for a couple of weeks, and it will make you proud of your achievement. Start with these easy orchids Lady's slipper orchid Cattleya orchid Moth orchid The following groups of orchids are among the easiest to grow indoors. Most orchids in these groups are considered intermediate-growing orchids in terms of their temperature needs. That is, they prefer minimum winter-night temperatures around 60° F, and from 70° to 85° during the day.Lady's slipper orchidsTropical lady’s slippers (Paphiopedilum spp. and cvs.) are small to medium, with showy, long-lasting, waxy flowers and leaves that are often mottled. They are perfect for indoors, since they can tolerate lower light. They do not like to stay dry for more than a day or two, especially when growing or blooming. Bloom season is winter and spring.Cattleya groupThis group includes species and cultivars of Cattleya, Laelia, Rhyncholaelia, Sophronitis, and their hybrids. Plants are small to medium and produce medium to large brightly colored flowers. To bloom, they need filtered bright light. The potting mix should be very dry before the plant is watered. Bloom time is winter into late spring. Moth orchidsThis group includes species and cultivars of Doritis and Phalaenopsis, some of the easiest orchids to grow. These medium-size plants produce sprays of small, medium, or large flowers that can last for months. They prefer filtered light and regular watering, with short dry periods. Blooming continues from winter into late spring. View the discussion thread.