Orchids: Rx for Winter Doldrums

The cold, dreary days of January have many of us day-dreaming about jetting away to some exotic location to bask briefly in a tropical paradise before having to return to the bone-chilling reality of a typical Midwestern winter. Such a getaway is not within the realm of possibility for most of us, but here is where plants can help.

Orchids have long held the reputation of being exotic plants and while they cannot affect the outdoor temperature, they can transform the average home into a tropical setting through their vivid, colorful blooms.

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There are more than 35,000 species of orchids that exist in nature, and most fulfill their reputation of being difficult to grow as house plants. There are, however, several orchids that can be grown successfully under normal home conditions and are becoming increasingly easy to find in retail outlets.

Probably the most user-friendly orchids for the average homeowner are species and hybrids of the Cattleya, Phalaenopsis and Paphiopedilum genera. When the average person thinks of an orchid they usually picture a cattleya, and success in growing cattleyas has been known to lead to a life-long addiction to orchids as a hobby. They produce spectacular, large flowers in colors including white, orchid, pink, red, yellow and many combinations thereof. Cattleya flowers have two large horizontal petals and a lower petal called a lip. Among these three petals are smaller sepals; many cattleya flowers are pleasantly fragrant. Cattleya plants have stiff, upright leaves with a storage structure called a pseudobulb at their base. Their growth is described as sympodial, which means that new shoots arise from the base of the rhizome of older growth.

On the other hand, phalaenopsis have a monopodial growth habit in which a compact central stem exists. New growth is added each year to this stem, and flowers are produced at the base of the leaves which alternate from sideto- side. Monopodial orchids do not produce pseudobulbs. Species in the genus Phalaneopsis are native to the jungles of tropical Asia where ample amounts of rainfall and humidity negate the need for water-storing structures. Phalaenopsis hybrids have very distinct flowers and often go by the common name of moth orchid because of their unique, flat shape. They usually are produced abundantly on long, arching stems and come primarily in white and shades of pink.

Both cattleya and phalaenopsis orchids are epiphytic in nature. This means they use another plant for support and derive water and nutrients from rainfall and organic debris on their host plant. In containers, ephiphytic plants are usually grown in a medium that remains very loose and laden with air. For orchids such as cattleya and phalaenopsis, orchid bark and osmunda fiber are two popular choices for a growing medium. When the growing medium decomposes to the point where it loses porosity and becomes dense, roots will suffocate and plants will weaken. Plants should be repotted when growth weakens; this usually is about every third year in the average home. Pots used to grow orchids should be porous–clay is ideal. Orchid pots made of clay have additional slits cut in their side for greater drainage and air infiltration.

Paphiopedilums, or lady slipper orchids, derive their name from the shape of their unique flowers that comes in many different sizes and colors. The most easily-grown paphiopedilums are the mottled leaf; warm growing types that are semi-terrestrial in nature. This means they grow in humus and other material on the forest floor instead of on host plants as do ephiphytic orchids. An ideal growing medium for terrestrial orchids should retain moisture yet be very well-drained. Finer grades of orchid bark or mixes containing orchid bark and various amounts of perlite, sand and/or sphagnum peat moss are ideal. Repotting every 18 to 24 months is sufficient.

Light is key to the growth of any plant, and orchids are no exception. Cattleyas need light between 2,000 and 4,000 foot candles whereas phalaenopsis and paphiopedilums need only between 1,000 and 1,500 foot candles. The latter is characteristic of the light required for good growth of African violet and can be provided using fluorescent lamps. Place the orchids 12 to 15 inches away from the bulbs and run the lights to correspond with natural day length. For any type of orchid, avoid exposure to direct sunlight which can burn the leaf and cause black lesions to form. Plants grown in a southern or western window should have a sheer curtain placed between them and the window for shading.

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Watering (arguably) is the most critical cultural practice when growing orchids. Since phalaenopsis and paphiopedilums have no pseudobulbs for water storage , a thorough drenching every five to seven days is recommended, depending on environmental conditions. For Cattleyas, the length of time between watering can be extended to 10 to 14 days. Drenching means placing each pot in a container of water up to the pot’s rim and allowing it to remain for several minutes to thoroughly soak the growing medium. An orchid fertilizer can be added to the water at the time of soaking. High nitrogen fertilizers (e.g., 30-10-10) are recommended when using bark as a potting medium. Avoid the build-up of soluble salts in the potting medium since this can quickly injure an orchid’s delicate roots.

Temperature is another critical aspect of orchid culture. Phalaenopsis and mottled-leaved paphiopedilums like warmer temperatures and should be grown at 75 degrees during the day and 65 degrees at night. Cattleya can be grown slightly cooler with daytime temperatures near 70 degrees and night temperatures close to 60 degrees being preferred. In both cases, the night temperature is more critical than the day temperature to the growth and wellbeing of the plant. Most orchids prefer humid conditions (60 to 70 percent). Since this is well above the average humidity in the home (especially during winter months) steps should be taken to increase it. This can easily be done by setting plants on gravel or a similar material in a tray and keeping the bottom of the tray filled with water. Home humidifiers can be used to increase the humidity in larger areas such as hobby greenhouses.

Most orchids are relatively pest free. Mealybugs and scale are the most problematic insects and should be dealt with before infestations become established. Careful inspection of new plants or plants that have been moved indoors after being outside all summer is helpful. Diseases can be minimized through strict sanitation procedures and providing adequate air circulation around the plants. Watering early in the day to allow for rapid drying of foliage also is helpful.

A noted horticulturist once remarked, "If you can grow an African violet, you can grow an orchid." While this might not be true for all species of orchids, it accurately depicts the ease of culture of a number of popular types that can add a festive, tropical atmosphere to an otherwise dull winter day.

Dave Trinklein
Associate Professor of Horticulture
573-882-9631