Different types of potting mediums are used in orchid culture. Many orchid plants are grown in osmunda fiber. The tough, wiry fibers break down very slowly and is an ideal potting medium. They are also grown in pots filled with chips of bark, stones, treefern, charcoal pieces or some other loosely packed material, which keeps roots well-aerated and permits water to drain quickly.

Fresh pine bark is also a popular medium but is usually mixed with other amendments before use. Both materials are sometimes mixed with peat and perlite or vermiculite. Some orchids are even grown in pebbles mixed with bark.

Most varieties (vandaceous orchids, some Phaleanopsis, and some Dendrobiums) can be grown quite easily in wooden slatted baskets, without any compost at all, but obviously, this culture demands daily watering. Some (Cymbidiums, and Cattleya varieties) do well in a mix of bark chippings, mixed with a little perlite, and charcoal to keep it sweet.

Some (Paphiopedilums and Phragmipediums) seems to do better in a mix of rockwool, a little sphagnum moss and some perlite, (or at least they do for us), and a pinch of dolomite lime does not go amiss with some of the Chinese species.

Planting

Orchids grow slowly compared to houseplants. However, most orchids need to be repotted about once every two years.

To pot an orchid, the pot is filled about two-thirds with orchid potting medium, then the plant is set in the pot with its roots spread out. The growing tip either centered (monopodials) or placed two fingers from the pot rim (sympodial). Then additional media is packed tightly around the plant to hold it in place.

You should be able to turn the pot upside down without the orchid or medium falling out. Practice will insure successful repotting. When the plant outgrows the pot by extending the new shoots over the edge, usually about every two years, it is time to repot.

Watering

Watering is the most important factor in orchid culture. Watering frequency depends on the growing medium, time of year, state of plant activity, and environmental conditions, and it should not be done on a fixed schedule. Water orchids thoroughly, usually about once a week, then allow them to dry slightly before watering again.

Orchids should be watered about once a week when the soil becomes dry. If the plants are grown in pots suspended in the air, they will dry out more rapidly than bench grown plants and will need watering more frequently. Orchids potted in bark require more frequent watering than those in most other potting media.

Temperature

Orchids are usually classified as warm growing, intermediate and cool growing, with regard to their temperature needs. The temperature groupings refer to the lowest temperature the orchid prefers during winter nights. Warm-growing orchids, such as phalaenopsis, sulk if temperatures drop much below 60F.

Intermediate growers, such as cattleyas, prefer winter nights around 55F. Cool-growing orchids, including cymbidiums and odontoglossums, are accustomed to winter nights of 50F. At the other extreme, most orchids perform poorly when exposed to temperatures above 90F.

Light is undoubtedly the most important factor in determining whether or not an orchid will flower. The light requirements for orchids vary with the individual plant. Many orchids require partial shade and can be grown in a greenhouse or outdoors. Four hours of sunlight is the minimum requirement during the winter and in the absence to natural sun, the necessary light can be provided with the use of flourescent grow lights.


Fertilization

Orchids do not require abundant doses of fertilizer. But to maintain healthy plants and see blooms on a regular basis, fertilize orchids with soluble plant food with a 20-20-20 analysis or a 30-10-10 orchid special fertilizer. Don't fertilize more than once a month. Apply the fertilizer in place of a normal water application. It is always best to use fertilizer at 1/2 the recommended rate. More orchids are killed because of over-fertilization and over watering than by any other cause.