Do Phalaenopsis Orchids Need Dirt?

Natural Growing Habitat

• Moth orchids do not grow in soil. Their thin, leathery roots are used for clasping onto rocks or other other plants, such as the stems of palms or tree bark. Therefore, botanists consider moth orchids epiphytes rather than terrestrial or ground-dwelling orchids. Soil is too dense for moth orchid roots. Planting in soil reduces air around roots and tends to hold too much water, which leads quickly to root rot.

Orchid Potting Mixes

• Growing moth orchids on large trunks or branches outdoors is possible only in frost-free regions, such as those in U.S. Department of Agriculture plant hardiness zones 10 and warmer. These orchids do grow well in containers and hanging baskets. Instead of soil or regular garden potting soil mixes, orchids are grown in organic or inorganic mixes of large, porous materials. Bark nuggets, crushed coconut husks and coarse sphagnum moss are common organic orchid potting mix materials. Inorganic materials include charcoal, lava rock, clay pellets, gravel, vermiculite and perlite. Potting mixes can contain a blend of both organic and inorganic particles.

Potting Mix for Moth Orchids

• Always use fast-draining potting materials for moth orchids. Avoid small particles that hold too much water and prevent good air flow. Moth orchid roots need to readily grow through the potting mix. Bark particles, sphagnum, clay pebbles, small lava stones and pre-made orchid potting mixes all suffice. Never use soil-based potting mixes or mixes made with sand.

Repotting Moth Orchids

• Sphagnum moss and small-sized bark particles decompose more quickly than inorganic or more coarse organic materials in the orchid pot. Moth orchids need repotting every one to three years. If the potting mixture is not decomposed and still has porosity and structure, repotting may be delayed by six to 12 months. To prevent loss of flowers and reduce plant stress, move moth orchids to a different pot only in late spring, when a flower spike no longer displays flowers.