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.
