The beauty, complexity and incredible diversity of orchid flowers are unrivalled in the plant world. These exotic beauties comprise the largest family of flowering plants on earth, with over 30,000 different species, and at least 200,000 hybrids. Orchids can be found in the equatorial tropics, the arctic tundra, and everywhere in between. The reason for this diversity lies in the orchid’s amazing ability to adapt to its given environment. With so many different orchid varieties that thrive in so many different growing conditions, it is relatively easy to find an orchid that is well suited to the conditions that you can provide — whether it is a kitchen window or a full-size greenhouse.
Most cultivated orchids are native to the tropics. In their natural habitat, they attach themselves to the bark of trees, or the surface of other plants. Their thick, white roots are specially adapted to absorb moisture and dissolved nutrients. Because these tropical orchids usually grow high in the trees, rather than on the forest floor, they are accustomed to good air circulation and plenty of light. They prefer a 12-hour day, all year-round, and require a high intensity of light — about the same as midsummer conditions in temperate regions.
Orchids are usually grouped into two broad categories that characterize their growth habits. Monopodial orchids have a single, upright stem, with leaves arranged opposite each other along the stem. The flower stem appears from the base of the uppermost leaves. Orchids with this growth habit include the phalaenopsis and vandas.
The more common growth habit is sympodial. These orchids grow horizontally, sending out new shoots from the old rhizome. Leaves and flower scapes form at the top of the new shoots. Many sympodial orchids form pseudobulbs, which are swollen shoots that store water and nutrients to help the plant survive periods of prolonged drought. Sympodial orchids include cattleya, cymbidium, oncidium and dendrobium.
Warm-climate orchids, including cymbidiums and dendrobiums, are accustomed to an average temperature of 55° to 70°F, a steady supply of moisture, and good air circulation. They are generally happy in a south-facing window, though they may need a little shading during high summer.
Cattleyas and some oncidiums grow where days are dry and relatively cool. They are able to tolerate a long dry season with temperatures of 80° or 90°F, followed by a distinct rainy season. Their need for light is high, so they should be placed in a sunny, south-facing window.
High-altitude orchids, such as masdevallia and epidendrum, grow in the cloud forests where average temperatures are 60° to 70°F, and humidity is very high. These orchids prefer filtered light that is not too intense.
Caring for Orchids
With 30,000 different species of orchids, it is impossible to give general care and cultivation instructions. However, how an orchid looks can provide clues to its preferences for light, water, and growing medium.
If the plant has few leaves, or leathery leaves (like most cattleyas and oncidiums), it’s likely the plant needs a high-light environment. If the leaves are soft and limp (like some phalaenopsis and most paphiopedilum), the plants are probably very light-sensitive, and should not be placed in a sunny south-facing window.
Humidity: Most tropical orchids prefer humidity levels of 60 to 80 percent. With the winter-time humidity level in most homes hovering closer to 30 percent, orchid growers often use a humidifier, or set their orchids in special humidity trays or gravel-filled trays. Some orchids also benefit from being misted.
Fertilizer: Orchid-growing mediums provide very few nutrients, so orchids must be fertilized to sustain healthy growth. Use a liquid fertilizer, and dilute it more than you would for other plants. Fertilizer should only be applied when plants are in active growth. This means that most orchids should not be fertilized in midwinter, or right after they have been re-potted. Many growers use a 30-10-10 fertilizer, though others prefer 10-10-10 or 10-10-30. Misting your orchids with fish emulsion or seaweed extracts will provide micronutrients.
Potting and repotting: Orchids are usually happiest in a relatively small pot. Plastic pots are preferred because when it’s time to re-pot, the roots can be more easily detached, or the pots can simply be cut apart. To ensure good drainage, you can fill the bottom inch or two of the pot with foam “peanuts.” Suspend the orchid over the pot, and gradually fill the pot with fir bark chunks or whatever other growing medium you are using. The crown of the plant should be just a bit below the top of the pot. Sometimes it’s helpful to use a bit of wire to secure the plant until its roots get established.