Bear one thing in mind when potting orchids: Don't use glazed or painted earthenware pots! Though decorative, they are damaging to plant growth. They keep the compost overwatered and underaired - both fatal to orchids. Otherwise, potting orchids - except for the trick of packing osmunda - is no different from potting azaleas or begonias.
Select a clean pot several inches wider than the broadest basal width of a terrestrial orchid. Soak it for a few minutes in tepid water, then drain. Place coarse gravel, small rocks, or crocks (bits of broken pots) in the bottom third of the pot.
Add several large handfuls of compost and shape to a cone, the top of which is on a level with the lower rim of the pot. Spread the roots of the terrestrial orchid carefully and evenly around the cone, and fill with additional compost. Firm the compost lightly to settle it - never pack it - and water thoroughly. Later, water sparingly until growth is established.
Some deciduous orchids, as Calanthe vestita, lose their roots. Push their pseudobulbs into the compost just far enough to hold them erect. Other terrestrials, those without pseudobulbs such as Oncidium cavendishianum, may have to be wired or staked to the top of the compost since their leaves would rot if covered.
The first time you attempt to pot a tree orchid in osmunda you will find yourself using the least desirable words in your vocabulary. There is a definite trick in handling osmunda. Old-time growers regarded potting as the most distasteful part of orchid culture.
It was once believed that osmunda had to be packed into pots with great pressure, using special sticks as levers. If, when you lifted an orchid by its foliage, the osmunda came free from the pot your education in orchid culture was considered highly dubious
POTTING EPIPHYTES IN OSMUNDA
It is now believed that such extreme measures are not advisable. As long as osmunda stays securely in place, holding its shape when knocked out of the pot, orchids will do satisfactorily. The trick in potting with osmunda is to handle it while it is slightly damp. It is pliable then and packs more easily. When it dries out it stiffens enough to firm itself in the pot.
Here is how you go about potting epiphytes. Take enough pieces of osmunda, sometimes called "orchid peat," to fill several pots. Soak the osmunda overnight in a pail of water. The following morning leave the pieces in a cool, dry, shady place. In the evening when you come home they should be just right for potting. They will feel soft, pliable, and somewhat damp - not wet - to your touch.
Take a clean pot at least two inches wider in diameter than the base of the orchid, soak it in tepid water for a few moments, then dry it out a bit. Soaking is not always necessary, but it helps the osmunda slide down the clay sides of the pot. Set the pot on its base and add enough gravel or crocks to fill it one-third.
Take the orchid in your left hand, the base (rhizome) resting on top of your thumb and forefinger. Smooth the roots over the back of your hand. Select a piece of osmunda as nearly conical in shape as possible. Put it beneath the base of the orchid, touching the rhizome.
Spread the roots around it. With other pieces of osmunda - slightly less in length than two-thirds the depth of the pot - cover the roots. Work outward, in a circle, until the osmunda covering the roots is a little larger in diameter than the top of the pot. Squeeze the osmunda with both hands, pressing it into the pot with a sliding motion.
Further packing is accomplished by inserting the fingers of your left hand between the osmunda and the side of the pot. In the gap so formed slip another small piece of osmunda. Turn the pot slightly and repeat the process. Keep turning, squeezing, and adding osmunda until you have to exert some pressure; then stop.
Now you can pot your orchids knowing exactly how you should go about it.