Formerly only osmunda fiber was recommended as a potting material; it required tedious soaking and packing of the pot. Today there is readily available the economical white firbark. It comes in graded sizes, is easy to handle, and is suitable for potting the epiphytic orchids, including the rock-growers. In firbark the growth is vigorous and circulation of air around the roots is assured. I have also successfully grown small plants of the terrestrial type in firbark, but they can be potted in the same soil mixture you use for your other plants.
Potting with firbark alone is a simple matter in the special orchid pots that have large drainage holes. First fill the pot about one-third up with broken crock. This is particularly important if seedling-size grade of firbark is used without sufficient crocking, this will wash through the big drainage holes. Position the plant in the pot with roots spread out over the crocking. Then fill in with firbark to within an inch of the top while you firm the bark around the roots with your thumbs, just as you do when potting plants in soil. Water well to settle the bark. This will hold the plant erect while you stake it, if this is necessary. In any case, pot securely; wobbly plants do not thrive.
After a few weeks, orchids in firbark alone require frequent watering until the bark has become well saturated. The epiphytes with aerial roots and pseudobulbs cattleys and odontoglossums while requiring a certain amount of moist air around the roots need to dry out somewhat between waterings. Phalaenopsis and other monopodial orchids that do not have pseudobulbs, as vandas and cypripediums, are watered enough to keep the potting medium damp but not soaked.
Terrestrial and semi-terrestrial orchids cypripediums and cym-bidiums require abundant moisture, but there must be good drainage to prevent sogginess. Mine are watered thoroughly every other day throughout the year, except during rainy periods; then, especially in winter, I skip an extra day or two, depending on the duration of the dull, wet weather.
Firbark is deficient in nitrogen, so feeding is essential. Apply any soluble orchid plant-food or fish emulsion as the manufacturer's directions indicate. With the exception of cymbidiums, orchids seem to require less nourishment than other plants, and on this account dilute applications of fertilizer are often advised.