Growing media is an essential part of any hydroponic growing system. Almost any inert material can be used in place of dirt or soil in a hydroponic growing system, although porous materials generally are recommended in order to hold the moisture and oxygen that allow the roots to grow properly. Growing media is not designed to provide any nutrients to the plants, so it should not break down or decompose quickly. The sole purpose of growing media is to offer support and moisture to the plants. While there are many types of growing media available, some growers tend to prefer one type of growing medium over another, especially depending upon the type of hydroponic system and designed being used. There are a wide variety of factors to consider when choosing a growing medium for your hydroponic system.
One of the most commonly used growing media in hydroponic gardening is rockwool, which is a porous, non-degradable material primarily made up of granite or limestone that has been heated, melted, and turned into small threads that eventually make up blocks, sheets, or cubes. You must soak rockwool in pH-balanced water prior to use. Because rockwool is so porous, however, you must not allow it to become completely saturated, or your plants could suffer from stem or root rot.
Another popular growing media is coconut fibre, which comes from the outer husk of coconuts. Coconut fibre is a completely organic plant material that was once considered a waste product. It breaks down very slowly over time, it is pH neutral, and holds a great deal of oxygen and water, which is ideal for hydroponic gardening. Some growers also have found that coconut fibre provides plants with some protection against certain root diseases.
Perlite and Vermiculite
Both perlite and vermiculite are mineral substances that expand when exposed to very high temperatures. Both materials are extremely lightweight and porous, which makes them appropriate for hydroponic gardening. While perlite doesn’t retain water, however, vermiculite does. As a result, some growers commonly mix perlite and vermiculite to use as a growing medium for their hydroponic systems.
Unlike other types of growing media, lava rock is not porous and due to the air pockets between rocks, water will easily drain through it. These same air pockets do provide sufficient oxygen to the plants and the ease in drainage will prevent your plants from becoming over-saturated. When using lava rock, it simply may be necessary to allow for more frequent watering and/or add other growing media, such as coconut fibre, to assist in moisture retention.
These are a few examples of the most commonly used types of growing media for hydroponic gardening. Additionally, other porous materials such as sand, oasis cubes, floral foam, polyurethane foam insulation, composted pine bark and pine shavings all can be used for hydroponic gardening, although they are not the most commonly used types of growing media. While there is not one type of growing media that is best for all situations and hydroponic growing systems, growers can easily find an effective type of growing media that works best for them.