Gardeners new to orchid growing soon realize that healthy orchids don’t grow in regular potting soil. The choices available in orchid potting materials can be confusing. Many orchid cultivars can grow in a one-ingredient medium. Making your own custom orchid mix is fun when you get to know the needs of your plant. Many high quality orchid growing media have similar benefits, so cost, availability, and appearance may help you narrow down your choice.
Brick Pieces and Cobblestones
Brick chunks add weight and stability to heavy orchid pots. Brick is somewhat water retentive, increasing humidity for your orchids. You'll want to find smaller sized pieces, especially because brick can be so heavy. Cobblestone works well as an anchor in the bottom half of an orchid pot. The small, uneven rocks are heavy, which helps top-heavy orchids like dendrobiums stay upright. Cobblestone will not retain water, so you'll need help to increase drainage properties of your orchid mix.
Coconut Coir and Husk Chips
You can use coconut coir alone or as part of a custom orchid mix. The long fibers absorb moisture, but also drain quickly, so orchid roots experience moist but not soggy growing conditions. A renewable resource, coconut chips come in different sizes to meet your needs as a standalone growing medium or a potting mix additive. The chips decompose slowly, ensuring maximum air circulation for orchid roots. Orchid growers can also look for coco husk fiber plaques, which provide an excellent substrate for growing orchids on mounts.
Anyone with a vintage bottle of wine is familiar with the watertight qualities of cork. You can mix water-shedding cork with water-absorbing sphagnum moss or shredded bark for an ideal orchid mix. The larger cork chips offer many crevices for orchid roots to explore.
Expanded Clay Aggregate
If you’ve wondered about those rocks in your orchid pot that look like Cocoa Puffs cereal, you probably purchased a plant grown in an expanded clay aggregate like Aliflor or Hydroton Clay Pebbles. Unlike regular rocks, these ceramic pebbles are porous, lightweight, and are neither acidic nor alkaline. You can use them alone, mix them with other growing media, or use them as a mulch on all of your orchids to give them a uniform appearance.
You will commonly see this inorganic growing medium used in orchids imported from Hawaii. Like other rock growing media, lava rock won’t break down and is a good potting mix amendment for orchids that don’t like to have their roots disturbed. Lava rock retains water, increasing humidity for your orchids.
Perlite, also known as sponge rock, is actually the end result of volcanic glass exposed to high heat. Although perlite doesn’t contribute any nutrients to orchid plants, the substance has excellent water retention and aeration properties.
Pumice has many fans for its polishing potential on rough skin, but this volcanic rock is also a lightweight inorganic growing medium for your orchids. The rock is highly porous, holding up to 50% of its weight in water. It's also quite lightweight, so won't weigh your plant down.
The cotton-like fibers of chalk and basalt will never break down in your orchid potting mix. Balance the alkalinity of rock wool cubes with an organic ingredient like bark or peat moss. This can be found in better gardening stores or online.
Shredded bark from trees like fir, cedar, and cypress acidifies your orchid mix as it breaks down. Bark is also favored for its natural look and pleasant fragrance. Orchids growing in a bark medium may need repotting once a year.
Weed and pathogen-free sphagnum moss maintains a moist environment for your orchid roots without becoming soggy. Often sold in compressed bricks, you must re-hydrate the moss and pack it loosely into your orchid pot for best results.
Orchids that like periods of dryness may thrive when grown in a Styrofoam medium. Simple Styrofoam peanuts can work as a growing medium and are an eco-friendly option. You can also buy special Styrofoam pellets like Aerolite, which is produced specifically for epiphytic plants.
Vermiculite combines well with sphagnum moss to create a light, moisture retentive orchid mix. The mineral is usually sold in gravel-sized particles. It can be found in better gardening stores or online.