Growing Media for Temperate Terrestrial Orchids

There have been many media used to cultivate temperate terrestrial orchids. We have used many of them in different situations. In the description of each genus we have included the media that we commonly use. Here, we discuss several of the media components.

These are the components of our typical Cypripedium mix. On the left is Schultz Aquatic Plant Soil®, on the right is Espoma Soil Perfector®, and in the lower middle is natural aquarium gravel.

Coir

Coir is the fibers of coconut husks. It is commonly used as a component of media for hydroponics since it holds water well but does not degrade rapidly. Coir is usually purchased in the form of a "brick" that is placed into water overnight to swell. The next day it will have swollen to several times its dry, compressed volume and can be broken up readily into a fine organic material that is used mixed with other media components.

Gravel

The best gravel to use for orchid media is "natural aquarium gravel" sold by Estes. This material is quartz or "silica sand" and is also available, usually for a lower price, as #3 filtration sand from water treatment companies or #2 chicken grit from feed supply stores such as Agway.

Perlite

These are the primary media components for our Cypripedium mix. On the left is Schultz Aquatic Plant Soil®, on the right is Espoma Soil Perfector®, and in the lower middle is natural aquarium gravel.

Perlite is a naturally occurring volcanic glass. To make perlite useful as a medium component, it is heated to high temperature which causes it to expand greatly. It is then processed to convenient particle sizes. This expanded perlite is very light - it floats on water. It allows a growing medium to retain excellent flow characteristics but it also holds a large amount of water which is released back to the medium as it dries.

Soilmaster®

There are several brands of fired clays that are useful as components of growing media. Pro's Choice Soilmaster, sold by Lesco landscaping stores, is montmorillonite clay that has been ground to an appropriate particle size, then fired at high temperature. This leads to an increase in natural porosity and results in a rigid, ceramic-like particle that will last for several years. The material does not float but holds water while contributing to a very open medium structure. A similar product is Turface®. Perhaps the easiest brand of the same material to find is Schultz Aquatic Plant Soil®; we purchase this at Home Depot.

Soil Perfector®