5 Most Common Soilless Mediums
The decision has been made: You want to grow something with this great system you’ve heard about called hydroponics. Maybe you’ve already decided what type of system you like, or maybe you aren’t sure where to start. For either case, you’ll need to decide on what kind of growing medium you want to try. Hydroponics systems don’t use soil, which opens up an entirely new world of grow media for you to choose from. So what is a growing medium? Aside from an adolescent psychic, growing mediums are the soil substitutes used in hydroponics, such as soilless potting mix, perlite, or coco coir, that support your root system and retain nutrients. Each type has different properties but the most important characteristics to consider are water retention, aeration, and pH neutrality. There’s an overwhelming number of medium types and recipe mixes, so let’s go over the most popular media.
Coco Coir
Right out of the gate, coco grow mediums are the greenest and most humanitarian grow mediums on the market. Coco is made from the discarded husks of the coconut industry. Coconut husks help coconut seeds germinate while protecting them from sun and salt-water damage. In the same way, coco grow media such as coco coir help seeds and seedlings start strong while protecting them from harmful fungi. Coco coir also has an excellent air to water ratio with great water retention. The high water retention rate makes it a poor choice for ebb-and-flow systems but makes it perfect for drip or wick systems. In a drip system, a balanced mix of 50% coco coir and 50% clay rocks works really well.
Rockwool
Rockwool is a fibrous material made from melted rock that is spun into long, thin fibers to make a wool-like media similar to fiberglass. It’s a very common material used from germination throughout the life of the plant and, similar to coco, has excellent water retention due to its fibrous nature. Unfortunately, rockwool is very difficult to dispose of since it isn’t bio-degradable, and the dust from brand new rockwool is hazardous to your health. You should always immediately soak and rinse rockwool after removal from its package, as well as wear eye and respiratory protection during handling. Even if you aren’t worried about the dust, rockwool should always be pH balanced by soaking it in pH balanced water before use. Otherwise, it is a very easy-to-use growing medium for drip and wick systems.
Expanded Clay Pellets
Expanded clay, hardened into a porous but solid ball, is one of the most popular hydroponics media around. Clay pellets drain quickly, are pH neutral, and add no extra nutrients to your hydroponics solution, keeping it clean. Unlike most mediums, clay pellets can be cleaned and reused, which helps save money in the long run. The spheres leave plenty of open spaces for roots to grow throughout the media while making drainage in an ebb-and-flow or direct water culture system very easy. Again, a 50/50 mix of clay and coco creates a breathable medium with great water retention. Be warned that a bed of clay pellets is extremely heavy.
Potting Soil (Perlite/Vermiculite mixes)
Many growers use a soil-like mix consisting of perlite mixed with other things such as coco coir or vermiculite. Both perlite and vermiculite are synthetic materials that are air puffed or heated until puffed (respectively) to produce a light and porous material that is excellent for oxygen retention. This media has many of the same benefits of coco, but any hydro system using it needs a very good filtration system to keep particles out of their recycled solution and water pumps.
Growstones
Growstones are recycled glass that’s been mixed with calcium carbonate to form a lightweight and porous substance similar to lava rocks, as in the case of pumice. Growstones are entirely sustainable and have fantastic water and air retention. As a trade-off, growstones are almost impossible to clean and re-use. Their porous nature leads to roots growing within the rocks and leaving behind plant matter that can affect your next crop. Be careful when transplanting from a growstone medium as they grip roots more easily, which can lead to root damage.
Depending on whether you need water retention or drainage, are worried over oxygen content of your water, or just need to avoid pH imbalanced mediums, there is always an option available. What do you use for your media and system? We’d love to hear about it in the comments below. You can also send us images of your systems through Facebook, Twitter, LinkedIn, Pinterest, or Instagram!
