Perlite
Perlite is an extremely lightweight , white , volcanic stone that is produced in grades ranging from less than 0.1mm all the way up to more than 3mm in size . It is a relatively inexpensive grow media that is pH neutral and is reusable as it does not biodegrade .
➤ PROS : Perlite is very porous which lends to good aeration , high oxygen retention , and waterholding ability . It can hold up to four times its weight in water . It is naturally sterile , so it is often used for seed starting , and young seedlings are less likely to die from damping off disease or root rot when started in perlite . It can be sterilised between crops and reused indefinitely .
➤ CONS : Its lightweight nature means it is prone to washing away when irrigated . It can also be easily blown away by fans when in its dry state . Perlite can also host algae growth which can lead to fungus gnat problems . Its dust is an eye , skin , and lung irritant , necessitating the use of gloves and a mask when handling dry perlite .
Vermiculite
Vermiculite is a media that is created when mica is heated at up to 2,000 ° F until it expands into little pebbles . It is then graded into various sizes , ranging from 0.1mm up to 8mm . Like perlite , it is a sterile medium and is fully reusable . It generally costs more than perlite , though .
➤ PROS : Vermiculite holds onto nutrients very well , making them available to plants for later usage . It is porous , so it has a high water-holding capacity and allows for good aeration .
➤ CONS : Vermiculite does not drain well . When it holds too much moisture , it can cause root rot or invite fungi to colonise . While it is reusable , it cannot be steam sterilised as it will disintegrate if heated ; other sterilisation methods must be used to reuse vermiculite . Vermiculite contains small amounts of asbestos and as such , it should be handled carefully .
Mineral Wool
Mineral wool , often known as stonewool , is a fibrous material that is created from superheating and then melting certain types of rock , which is then spun into threads to create various media products such as blocks , sheets , cubes , or slabs . There is little chance of running out of the raw material needed to make it , and it is non-degradable .
➤ PROS : Mineral wool easily absorbs water and also drains fairly well . It is comprised of up to 25 percent air , so it gives root systems good aeration when it is not fully submerged in water . It is a good medium for starting seeds , rooting cuttings , and for supporting larger plants like tomatoes . Slabs can be cut to any size desired . It is a long-lasting medium and can be reused if sterilised between crops .
➤ CONS : Mineral wool has to be buffered by soaking in a lower pH solution before it can be used . It needs to also be rebuffered between crops . When mineral wool is fully saturated and under water such as in some hydroponic systems , it can restrict root growth . Because it is non-degradable , it takes up room in landfills once it has used up its useful life . Mineral wool is highly irritating to skin , eyes , and lungs . Masking and wearing gloves are required to handle it before it has been moistened .
“ Some growers prefer to make their own mixes by using some of these ingredients and custom-blending them .”
Sand
Sand has been used as a growing medium for thousands of years . It is relatively inexpensive compared to other media options . Growers typically opt for coarser grades of sand to increase drainage and aeration .
➤ PROS : Sand is one of the most readily available media all over the world . Different grades of sand offer different benefits . Finer sand particles allow for translocation of water . Sand is easily reused after being sterilised and does not break down .
➤ CONS : Sand is not good at holding nutrients . Whatever the plants cannot use right away will be leached out . An exception to this is salt , which can build up to toxic levels if not periodically flushed . It is also not the most convenient medium because of its weight .
Floral Foam
Floral foam is a very inexpensive medium used for seed starting and cuttings , often for quickgerminating crops .
➤ PROS : Floral foam has a very high water-retention capacity and no pre-soaking is required to use it . It is versatile and can be used in almost any growing system , or even used within other growing media . It is available in any size needed .
➤ CONS : It is not an ideal medium for growing beyond the young seedling stage . It does not allow for any translocation of nutrients and does not have any buffering capacity if nutrient levels are too high . Pieces of the foam can easily break off and wreak havoc on filters in hydroponic systems .
This is by no means an exhaustive list of available media , just the most common types . Some growers prefer to make their own mixes by using some of these ingredients and custom-blending them with other nutrients , minerals , or other materials . Some other materials used as media include gravel , clay pellets , glass grow stones , rice hulls , pine bark , straw , sawdust , and lava rock or pumice . Others still just use water or field soil . Though it may take some trial and error , there is a blend out there that is right for you , your growing system , and your crops .
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