Expanded Clay Pellets

“Expanded clay pellets” are a tough granular medium, produced from clay formed into spheres and fired in rotary kilns at high temperatures. (1,200°C (2,190°F)).

The process causes the clay to expand and become porous. The shape of the pellets differs widely and so does the color although the light brown color dominates.

The following facts are of interest to orchid growers:

The pellets are light in weight, do not absorb water, do not compact over time, are inert, pH neutral, contain no nutrients, and allegedly prevent parasitic growth and root rot. Furthermore, the pellets are not biodegradable and can be cleaned, sterilized and re-used.

The “expanded clay pellets” are known under many “Trademarked” brand names like “Hydroton”, “Hydrokorrels” and are sold in many sizes from 4-8 mm, 8-16 mm, and larger.

The advantages of using expanded clay are very clear but their use in orchid culture is still in experimental stage. (Like Perlite 15 years ago).

The very large spheres, (3 cm plus in diameter) could be used in the cultivation of Vandaceous orchids. Spheres can only take up to 2/3 of the space in a pot the remaining 1/3 empty.

Smaller spheres (4-8 mm) could be used as a layer on the top of the Terrestrial potting mix to separate the leaves from the soil, thus preventing their rot.

A mix with 10-20% Perlite and 30-40% Coir may prove to be a good alternative to many potting mixes for a variety of orchids.

Expanded Clay Pellets are a very popular hydroponics medium.