The most widely-spread growing medium is, perhaps, rockwool. Originally used for insulation purposes and also known as mineral insulation, rockwool was first used as growing medium by Dane gardeners. Now, it is frequently used for drip-style indoor gardens around the globe.
Rockwool is produced by a process similar to making cotton candy: a particular mixture of sand and rock is melted and then turned into fibers by spinning the mixture to form products of multiple shapes and dimensions, from 1″ starter cubes and up to large slabs of 3″x12″x36″ in size. The variety of available forms and sizes turns rockwool into one of the most widely-used growing mediums.
Key advantages, as well as disadvantages, of this popular growing medium are listed below.
Rockwool’s Strong Points
HOLDING WATeR – rockwool as a growing medium in hydroponics systems is capable of holding a large amount of water. This creates an additional protection for situations, when water is not supplied because of power outages or failures in pumping or other gardening equipment.
ACCUMULATING AIR – up to 18 % of air are constantly kept by rockwool. Due to this capability, there is a very little risk to over water rockwool; besides, the plants are always supplied with enough amount of oxygen.
MULTIPLE SHAPES AND SIZES AVAILABLE – whether it is a small 1″ cube for seeds propagation or a large 3x12x36 inches slab for huge plant, rockwool offers a wide variety of shapes and sizes to choose from. Besides, loose rockwool is also available, designed for filling different plant containers.
NO DUST AND EASY TO USE – since rockwool maintains its form almost perfectly, it cannot be scattered accidentally. Besides, usually packed into plastic rockwool is a very clean material that is easy and comfortable to work with.
Rockwool’s Weak Points
NOT A “GREEN” MATERIAL – rockwool is claimed to be not environment-friendly material, because of its almost indefinite time of breakdown.
HEALTH HAZARDS – rockwool particles and fibers pose serious health danger, especially for human lungs. That is why it is necessary to wear a protective dust mask, while working with rockwoll.
pH PROBLEMS – because of rockwool’s high pH level, it is necessary to balance pH level in the nutrient solution properly and make it suitable for the plants, you are growing. In general, the use of rockwool requires more routine work to keep pH level of your nutrient solution at steady level.
LONG PRE-SOAK PERIOD – before rockwool can be used in the hydroponic system, it should be soaked for at least 24 hours beforehand. Other growing media usually do not require pre-soaking, it is enough just to well-water them.