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What’s The Best Growing Medium For Cannabis?

The sexy parts of your cannabis plants may be above ground, but it’s down in the root zone where the real magic happens. By taking in nutrients, water, and oxygen, a plant’s roots provide everything it needs to grow and produce top-quality bud. The growing medium largely influences the ability of a cannabis plant’s roots to do so, so picking the right substrate is a pretty important decision.

Soil – The Most Basic Cannabis Growing Medium

Plants have been growing naturally in soil for millions of years. It’s only logical to use this widely available material as a growing medium for cannabis. Cheap and easy to work with, the soil is probably the best choice for all novice growers. It’s also considered by many to produce the best-tasting weed.

Because soil contains many microorganisms that help regulate all aspects of the environment, much of the work is taken care of with little input required from the grower. Fluctuations in pH or other variables generally have less drastic consequences than they would in other growing mediums. So there’s more room for making mistakes.

Many commercial soils also come packed with nutrients, so there’s no need to add any extra fertiliser or plant feed. Not for t the first few weeks of the growth cycle anyway. Soil is also the most natural and environmentally friendly cannabis growing medium.

On the downside, soil can harbour pathogens and pests that could harm your plants. Additionally, the natural growth rate in soil is less than in other growing mediums. Some of which can support larger cannabis plants and greater cannabinoid yields.

Coco Coir – A Hugely Popular Cannabis Growing Medium

Coco coir is a by-product of coconut harvesting and has become extremely popular as a growing medium for cannabis. Made from discarded coconut husks, this fibrous material offers excellent water retention and aeration.

Because about a third of the fibres in coco coir repel water, air pockets are always present. Within such a structure, roots can grow and access nutrients much more easily than soil, which frees up more energy for plant and bud development. For this reason, cannabis plants grown in coco coir tend to grow faster and become larger than those cultivated in soil.

Of course, all this depends on the grower adding the right blend of nutrients into the mix. Coco coir itself is inert, which means it contains no nutrients and can’t support plants on its own. It also lacks any microorganisms found in soil, so growers are responsible for manually controlling every variable.

This is both a positive and a negative, as it allows for more control over the root zone environment and provides little leeway for making mistakes. Growers must continually monitor the pH level to ensure it remains within the optimum range and supplies the right blend of nutrients at each stage of the cannabis growth cycle.

Coco coir has excellent drainage and oxygenation and is a popular growing medium for cannabis.


Rockwool is the brand name for a type of mineral wool that is made from volcanic rock. Like coco coir, it has excellent drainage and aeration and has become a popular growing medium for cannabis.

Unlike coco coir, however, Rockwool is neither organic nor biodegradable. Its production involves intense industrial processes that are not environmentally sustainable. On the flip side, the fact that it contains no organic matter makes Rockwool impervious to harmful bacteria and fungi, drastically reducing the potential for plants to become diseased.

Growers must supply the correct water and nutrients while also maintaining the proper pH level throughout the growth cycle. If this is achieved, Rockwool can support rapid root growth, resulting in large plants with excellent yields.


Not strictly a cannabis growing medium, hydroponics is an umbrella term for various techniques that involve growing weed without soil. Hydroponic systems vary significantly in nature, yet all involve delivering nutrient-rich solutions directly to the roots of a plant at set intervals.

Some hydroponic set-ups use growing mediums like coco coir, Rockwool, or clay pebbles to anchor plants’ roots. In contrast, others simply suspend plants above a reservoir with their roots dangling down into the water. By eliminating the need for roots to search through soil for nutrients, these methods allow plants to direct more energy towards producing stems, leaves, and flowers.

The absence of soil also reduces the chance of disease and minimises the potential for nutrient ‘lockup,’ which occurs when nutrients become fixed in the soil and remain unavailable to plants. As a result of all these things, hydroponic systems allow growers to boost their yields considerably.

The trade-off is that hydroponics can be costly and complex, and therefore isn’t necessarily suitable for beginners. Plants grown this way can sometimes have a slightly unnatural flavour, which is why many people choose a more conventional growing medium for their cannabis.

Cannabis Growing Medium Mixes

If you can’t settle on a suitable growing medium, you can always mix and match. Adding coco coir to soil, for example, improves its structure and increases water retention and oxygenation.

Perlite, meanwhile, is a lightweight material made from volcanic glass, which attracts oxygen to its surface. Many cultivators add this to their cannabis growing medium to enhance aeration and minimise roots’ energy when seeking out nutrients.

Finally, some growers choose to add peat moss to their soil, though this is somewhat controversial. The process by which peat moss is extracted from peat bogs produces considerable carbon emissions and destroys local ecosystems, so some countries are considering banning it.

However, when added to a cannabis growing medium, peat moss massively increases water retention and introduces beneficial microbes that help make nutrients more available to plants.

Overall, it’s impossible to say which growing medium is the best for growing cannabis. Ultimately, this will depend on each growers’ needs, expertise and budget. With so many options, though, the choice is yours.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

This post is also available in: French

Ben Taub