Growing cannabis is both an art and a science. At scale, however, data-driven insights carry much more weight in that dynamic. The commercial production process of cannabis involves many small decisions. Each decision leads to a unique approach to cultivating this plant.
One of those decisions is selecting which growing media your team will use. This may come up multiple times in the course of a cultivation company’s life span; growers often switch from one medium to another, pulling levers to dial in the most effective approach for their business. For many cannabis growers, the draw of soilless media can provide benefits for both the artistic and scientific approach to cannabis.
These soilless media–including stone wool, coco coir, perlite, vermiculite, peat moss, and clay pebbles, as some of the most prominent examples–provide growers with distinct advantages over living soil counterparts.
Your Soilless Options
So, where does a cannabis grower begin?
First, identify your costs, your budget, and your long-term business goals. From there, work backward to identify a soilless option that fits your needs.
This decision is an important one at the outset of a new cultivation operation, but it’s just as important for soil-based growers interested in gaming out other options.
Stone Wool
Stone wool substrate blocks come from molten rock spun into cotton candy-like fibers. This product, sold by Grodan under the name Rockwool, is widely used for its ability to retain water and air. Stone wool is excellent for seed starting and hydroponic systems, but cannabis growers should note that it requires careful handling and pH adjustments.
This medium provides very high control over nutrient and water delivery, which, when managed correctly, can result in very high yields and excellent quality.
As with any switch to a new growing medium, growers will encounter a learning curve.
READ MORE: The Complete Guide to Stone Wool Growing Media for Indoor Cannabis Cultivation
Coco Coir
Made from the fibrous husks of coconuts, coco coir is pH-neutral, has good water retention and drainage, and is reusable after being cleaned and buffered. It's often used either alone or mixed with other media.
This is a widely used medium, but it comes with its fair share of challenges, like anything else in cannabis. Growers running their plants in coco must watch out for nutrient leaching, water retention issues, and even variability in the quality of the coco itself. Coco coir can sometimes bind with calcium and magnesium, making these nutrients less available to plants. This requires careful monitoring and possibly supplementing with additional cal-mag supplements.
Perlite
This volcanic glass is expanded through heating and is very light and airy. It's often mixed with other growing media to improve aeration and drainage.
Note that perlite itself does not hold nutrients well, which can lead to leaching and the need for more frequent fertilization. For growers mindful of the cleanliness of their environment, perlite can be dusty when handled. Its fine particles can be irritating to the eyes and respiratory system.
Vermiculite
Similar to perlite, vermiculite has a higher capacity to retain water, making it suitable for use in mixes where moisture retention is important.
That said, sometimes vermiculite can hold in too much water. This leads to waterlogged conditions which are detrimental to root health.
Peat Moss
Sourced from decomposed plant material in bogs, peat moss is acidic and has good water retention properties. It's commonly mixed with other media to create a balanced growing environment.
This one is tricky, however, Peat moss is not a renewable resource, and its extraction can be environmentally damaging. This makes it less favorable among environmentally conscious growers.
In the UK, for example, peat moss is not allowed as a growing medium. Around the world, including in North America, peat moss is losing favor as a sustainable option for growers.
Clay Pebbles
These are lightweight, porous, and have excellent drainage and aeration properties. They are often used in hydroponic systems, especially in flood and drain setups. Due to their size and shape, clay pebbles are generally not suitable for NFT systems where media like stone wool are preferable.
