Hydroponic growing media

Although there is no soil in a hydroponic garden, the plants must still be anchored.

There is a wide range of inert materials which can be used to support plant roots and we call them "growing media". Heydite, clay pellets, Perlite, vermiculite, and Rockwool are the most popular media. The hydroponic media that work best are pH neutral, provide ample support for plants, retain moisture, and allow space for good air exchange.

The type of media you choose will depend on the size and type of plants you wish to grow, and the type of hydroponic system being used.

For continuous drip systems, course media such as Hydrocorn (clay pellets) are best. The 1/4 " to3/4 " pebbles provide enough free drainage and air space to take advantage of continuous feeding. These media also provide good anchorage for larger plants, and are easy to clean and re-use indefinitely.

Rockwool is also another popular medium. Made from rock which has been melted and spun into fibrous cubes and growing slabs with the texture of insulation, Rockwool provides roots with a good balance of water/oxygen. Small cubes are used for starting seeds and cuttings, 3" or 4" cubes for small plants or intermediate growth, and slabs for larger plants. Rockwool can be used with continuous drip or flood and drain systems. Although it is possible to sterilize and re-use Rockwool, most often it is used only once.

Perlite, made from volcanic rock, is a white, light weight material often used as a soil additive to increase air space (it repels water). The 1/8" to 1/4" pellets can be used alone as growing medium, but don't provide enough anchorage for large plants. Perlite is often used to start seeds and cuttings, which can be easily transplanted after rooting.

Vermiculite is also used as a soil additive but unlike Perlite, Vermiculite absorbs water and is therefore used for water retention. The two are often mixed together. It is made from heat expanded mica and has a flaky, shiny appearance.

Soilless mix such as Pro-mix BX, and Pro-mix lite has the appearance and texture of light soil. Mainly peatmoss, mixed with Perlite, it contains very little nutrient, and is used a a soil additive, or alone as a hydroponic medium.

Some hydroponic systems do not require any growing medium at all. Various methods are used to support the plants while the roots are directly fed nutrient solution. Some examples of these are aeroponic, N.F.T. (Nutrient Film Technique) and deep water culture.

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