Orchid potting mix for moth orchids

Orchid potting mix for moth orchids

1. 01

   Why orchids can’t grow in regular soil

   In the wild, moth orchids grow on the branches and trunks of trees. Their roots are used to air and to drying out quickly.

   The RHS warns that multipurpose and loam-based compost will kill moth orchids. The Missouri Botanical Garden says regular potting mix leads to root rot and plant death.

2. 02

   What goes into a good orchid mix

   The Missouri Botanical Garden recommends a commercial mix labeled for Phalaenopsis. These are usually fir or sequoia bark, often with horticultural charcoal and perlite. Use medium-grade bark for a mature plant.

   UF/IFAS lists chopped tree fern fiber, osmunda fiber, charcoal and volcanic rock as other common ingredients. The charcoal helps neutralize fertilizer salts, according to the Missouri Botanical Garden.

3. 03

   Bark or sphagnum moss?

   Bark dries out quickly and forgives the odd extra watering. It breaks down over time, though, and then needs replacing.

   Sphagnum moss holds much more water. Iowa State says that makes overwatering and root rot more likely. In moss, water only when the top feels dry. For beginners, bark is easier.

4. 04

   How to make your own orchid mix

   The Missouri Botanical Garden mixes 5 parts medium fir bark in pieces of about ¼ to ½ inch (6 to 12 mm), 1 part horticultural charcoal and 1 part perlite. Do not use landscape mulch.

   Dampen the new mix before potting to rinse out fine bits, as Clemson Extension advises. Firm it only gently, because pressing hard crushes the perlite and makes the mix hold too much water.

5. 05

   When to replace the potting mix

   Bark breaks down over time. The RHS, UF/IFAS and the Missouri Botanical Garden all advise replacing it about every two years.

   Replace it sooner if brown particles wash out when you water, the bark at the drainage hole feels soft or the mix stays wet long after watering. Never reuse old bark.

6. 06

   Common mistakes

   Regular potting soil or cactus soil. Bark that is too fine for a mature plant. Landscape mulch. A pot far too big, full of mix that stays wet.

Common questions