Potting medium does more than simply root an orchid in place. It allows roots to breathe and provides proper air circulation and optimum moisture and nutrient levels. The right medium also gives your plant the proper drainage to prevent water logging. But with such a variety of potting media available, how do you know which is the right one?
Below are a few guidelines you can follow to help you make an informed decision.
Type of Fertilizer Used
Fertilize your orchid with a weak solution of balanced plant fertilizer. A balanced fertilizer should contain equal parts nitrogen, phosphorus and potassium (look for 20-20-20 on the label). Always use fertilizer at half-strength, diluting it with an equal amount of water before gently lifting the orchid’s leaves and pouring the fertilizer into the pot.
Size of Plant
The size of your orchid will affect the grade of your medium. One of the top orchid growers recommends medium grades of a bark-fir mixture (50 percent bark and 50 percent fir) for orchids in three and four-inch pots, coarser grades for orchids in six-inch pots and chunk-grade material for orchids in pots eight-inches or larger. For miniature Phals often sold in pots about two inches in diameter, sphagnum moss may be the best choice for potting medium. This is because the chunky growing media used in larger Phals is simply too large for their smaller pots.
Although coarse-grade materials aid in air circulation, which is important to root health, they aren’t ideal for retaining moisture. This can be a real problem in a low humidity environment. (Phalaenopsis orchids are known for their love of moisture!) Fine-grade materials dry at a slower pace, are less porous and retain more moisture; however lower porosity means less oxygen circulation.
Finding the best potting medium for your plant requires some trial and error on your part. Many orchid growers and owners opt to create their own medium recipes. For example, orchid experts at both the University of Tennessee and Texas A&M University have recipes they say yield them wonderful results.
If you decide to create your own recipe, the most common media materials to use are fir bark, sphagnum peat, tree fern, charcoal, sphagnum moss, perlite, coconut husk chips and diatomite. You can find all of these items online, at your local nursery and at retailers like The Home Depot.
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