What Kind of Soil Do You Use to Plant Phalaenopsis Orchids?

The Moth Orchid

• The genus Phalaenopsis includes about 60 orchid species native to the tropical parts of Asia and Australia. Because of extensive breeding for decades, there are now thousands of hybrids called grexes. Moth orchids are epiphytes; they clasp their roots onto the bark or branches of other plants, such as trees. These orchids do not grow in soil. In nature, the leathery roots adhere to bark or grow in loose pockets of decaying leaves and twigs in branch crotches or wedged in between rocks.

Potting Mix Types

• Three different basic types of moth orchid potting mix exist, according to the American Orchid Society. Bark-based mix comes from variously sized nuggets of tree bark. It drains water well, is relatively inexpensive but breaks down after 12 to 24 months in a container. Peat-based mixes resemble potting soil. However, peat used in orchid culture must be coarse and have additives, such as perlite, charcoal bits or foam packing peanuts, improving drainage and aeration. They also compact and decompose quickly. Inorganic mixes are made of small pumice stone or large clay particulates.

Potting Mix Porosity

• All potting mixes used for moth orchids must be porous, allowing full drainage of water. Manufactured orchid potting mixes exist making orchid growing easier and more precise for orchid hobby growers. The mixes often are rated fine or medium grade. Fine means smaller sized particles and is especially useful for growing tiny species or young, small-rooted seedlings. Mature moth orchids need a medium-grade textured mix.

Repotting Moth Orchids

• If properly grown, a moth orchid does not need annual repotting. Exposure of roots on the container or throughout the potting mix is natural and not alarming. Expect the need for a larger container every 2 to 3 years. The ideal repotting time for a moth orchid is in spring immediately after flowering ends. Gently pry the orchid and roots from the container, cutting off any shriveled, soggy, rotten or dead roots before placing it into a new container. Nestle orchid potting mix around the roots in a slightly larger-sized container with the crown 1/2 inch above the potting mix surface. The moth orchid's crown is where the roots join into a low stem and transition into the bases of leaves.