other potting materials

Orchid growers have tried many different materials for the artificial culture of orchids...and some of them have worked. To an orchid, the potting medium and container is merely a place to hang its proverbial hat;  just a support. You, the orchid grower, supply water, nutrients and air in the proper amounts to allow the plant to flourish. Any material that provides this support structure, and contains nothing toxic to the orchid, will work as a potting material. People have experimented with glass marbles, old tire chunks, mulch and other landscape materials, dried beef bones and cedar shingles as places to grow orchids. The most commonly used materials have been described. There are additional materials that will be briefly discussed here that also have a place in the culture of orchids. Be sure to read Rule #1 before experimenting with new potting materials.

Cypress Mulch Some growers have had success using cypress mulch or chips as an orchid potting material. Potential problems would be that, as a landscape material, it may come from unknown sources and could have contaminants harmful to orchids. Also, it is not graded by size - a bag of cypress mulch may have pieces 6 inches long mixed with 1 inch pieces. Cypress mulch has a tendancy to break down within a year or so and requires extra nitrogen (30-10-10 fertilizer).

Bagasse is the natural by-product of refining sugar from sugar cane. Being organic it probably provides some minor nutrition to potted orchids. The texture is too fine to be used by itself and requires additives to open up the mix. Bagasse is best suited for seedling culture or as an additive in other mixes, especially terrestrials.

Charcoal is available in many different grades and used extensively in orchid culture. Coarse charcoal (pieces 1 to 2") can be used in baskets as the sole media for vandaceous orchids or used in the bottom of clay or plastic pots as drainage. Medium grades may be mixed with bark or sphagnum to keep the mix open and sweet. Fine grade, or aquarium charcoal, is good for growing seedlings and is usually used in conjunction with sphagnum or peat which provides additional moisture. Charcoal will outlast most other potting media except for inorganics such as lava rock. DO NOT use charcoal briquettes at any time for growing orchids.

Coconut fiber,  also known as "Husky Fiber" or coir, has gone in and out of popularity as an orchid growing media. You may occasionally hear reports of somebody seeing outstanding root growth from using it. Then you'll meet someone who has killed off a portion of their collection with it. Coconut fiber will last at least a year in a container and seems to provide sufficient air space but many report that it stays too wet in a pot. It is probably best suited as a material for lining baskets.

Peat moss is used by many orchid growers as an additive to provide higher moisture retention. It is also frequently used in formulating mixes for terrestrial orchids, seedlings and in proprietary mixes offered by commercial orchid firms. Peat is a major component of so-called "mud mixes" popular among Phalaenopsis growers. It is available in both granular and chunks. Peat provides a small amount of nutrition to plants.

Perlite is regularly used in seedling and terrestrial mixes to keep them from compacting. It is inert and will last indefinitely. Perlite's light weight can make it tricky to work with until mixed with other materials. Turn off the fans before using. Although primarily used as an additive, some growers use sponge rock (large perlite) as a media on its own.

Redwood chips are not used as a potting media on their own but they are useful as an additive to tree fern, fir bark or any of the aggregates. It is reported that the presence of redwood chips discourages snow mold from growing. 

Rockwool insulating material known as "Grodan" is relatively new to the orchid scene yet it possesses many desirable qualities. It is available pre-mixed in various degrees of absorbancy/non-absorbancy from 80/20% (recommended for Phal.) to 60/40% (for Cattleya, etc.). The material is available as pellets or different size cubes as well as loose.  
            There has been some concern about inhaling rockwool fibers and the potential for respiratory hazard although no actual research has been done. Still, to be safe, wear a respirator or face mask when potting with rockwool. Pre-soaking the material in warm water with a few drops of liquid detergent will also significantly reduce the chance of airborne fibers. This procedure is a good idea anyway as rockwool is difficult to re-wet once it has dried out. You may need to adjust your watering practices to maintain plants evenly moist (not soaking!). Best to use other media for orchids that prefer to dry thoroughly between waterings.

Oyster, clam, mussel shells may be useful additives for certain potting mixes where additional calcium is required. This may be beneficial for certain terrestrial orchids. The shells may be broken with a hammer into the proper-sized pieces. Be careful!