The majority of popular orchids are epiphytic, that is they usually live up on trees in places like tropical cloud forests. Their roots serve to anchor them to a tree limb or other support, aid in photosynthesis (many growers like to use clear pots to allow sunlight to reach the roots), as well as taking in and storing water and nutrients. We grow them in pots because our homes are not nearly humid enough to keep the roots hydrated without a potting medium.
For epiphytic orchids, exposed roots, or roots clambering out of the pot, are not necessarily a sign that the plant needs repotting. Since these orchids technically do not even require a pot, they generally need to be repotted when the medium in which they are growing begins to decompose and break down, resulting in poor drainage. Terrestrial orchids will also need media replaced, or
may need to be divided or simply bumped to the next size container as the number of pseudobulbs increases.
Some signs that your orchid may need repotting include:
Repotting should only be done when the orchid is not in bloom or in bud. Remove old potting media from the roots of the orchid. Do this carefully, to avoid damaging the green growing tip of the root. Also protect the papery whitish epidermal tissue (velamen) of the root, which serves to capture water as it is poured through the potting medium. If the roots have adhered to the side of the pot or slat basket, or the potting mix sticks to the roots, gently soak the roots until you can free them.
Use the same sized pot if you are simply replacing old media, or the very next sized pot it the plant
needs more room. If you are dividing a large orchid, choose pots that will just comfortably hold the
Place some media in the bottom of the pot (use a medium appropriate to the type of orchid.) If drainage holes are so large that the medium sifts out, use chunks of hardwood charcoal, coarse rock or broken pottery to cover them (being careful not to inhibit drainage.)
After trimming off any dead or rotting roots with a clean razor blade, place the orchid in the center of the container, gently spreading the roots out inside the container. Holding the crown of the plant at the desired level, carefully pack the potting medium around the root system, filling in all the spaces between roots. A skinny wooden dowel is helpful in packing the medium in firmly. The crown should ultimately sit right on the surface of the medium.
Secure the plant in the pot with an orchid clip or a stake. Orchids that produce tall blooming spikes can have their flower stem secured to the stake when flowering.
Epiphytic orchids can also be grown on slabs of cork, bark, tree limbs, and tree-fern fiber. For a
re-mount, you may have to soak the current slab in water to loosen the roots. Again, be careful to avoid damaging the roots as you handle them.
Wrap the root system in damp long-fibered sphagnum moss, and then tie the plant to the slab with clear nylon fishing line or cotton cord. This can be removed once the orchid’s roots have attached themselves to the slab. Be sure to orient the slab so that the plant hangs in a natural position. Remember that most mounted orchids will have less water available to them, and may require more frequent watering or soaking.