The right soil for growing cannabis
One can get caught up thinking about nutrients and amendments in the soil, which are important, but the most important aspect of any soil is its texture, ability to drain, and overall water retention. For a cannabis plant to grow and thrive, it needs a good mix of water and oxygen at the roots at all times! Too much water restricts oxygen to the roots, while not enough water retention can dry out and injure the roots. For the best results when growing cannabis, a soil with a light texture that is good at retaining water is best.
Signs of good cannabis soil
- Appears dark and rich
- Loose texture
- Drains well – doesn’t pool on top of your soil for more than a couple of seconds and doesn’t take forever to drain out the bottom
- Holds water without getting muddy
- Example of “Good” Soil Ingredients– Composted forest humus, sandy loam, sphagnum peat moss, coco coir (coco fiber), perlite, earthworm castings, bat guano, fish meal, crab meal, bone meal, blood meal, Azomite, pumice, kelp, dolomite lime, mycorrhizae, and leonardite. These are some examples of cannabis-friendly ingredients you see the most often
Signs of bad cannabis soil
- Muddy, clumpy and waterlogged soil retains too much moisture making it easy to over-water your plants
- Wood Chips. Too many visible wood chips in the soil means it hasn’t been fully composted and all the nutrients in wood are mostly unavailable to your plants
- Thick and heavy soil holds too much moisture and not enough air
- Dirt from outside almost never works
- No “time release” chemical nutrients in the soil. These types of soil release nutrients slowly over the course of months. This provides too much nitrogen in the flowering stage, which can impair overall bud growth.
- Examples of “Bad” Soil Ingredients – You don’t want to see wood or bark on the label if it doesn’t say it’s been composted first. Also if you see just the word “fertilizer” in the ingredients, that’s often code for slow-release chemical nutrients, which you don’t want!
Suggested brands for cannabis soil
Growing in the US
Fox Farm has been around for over 30 years and makes some of the most common types of “cannabis soil”. They have several great soil mixes, including “Happy Frog” which is a great choice for seedlings and clones.
Their Ocean Forest soil mix is “hotter” soil (higher levels of nutrients) that contains ingredients that cannabis plants love, including earthworm castings, bat guano, fish meal and crab meal. The nutrients contained in the soil will provide everything your plant needs for several weeks. Although it might give young seedlings just a touch of nutrient burn at first, they can be started in Ocean Forest soil and will soon be able to use the nutrients and start growing quickly. Some growers might put a little bit of Happy Frog on top of a container of Ocean Forest, just to make it a little more gentle for seedlings the first week or two.
If you are willing to keep transplanting to bigger pots as your plant uses up the nutrients in the soil, you don’t need to supplement with extra nutrients. However, even if you grow in the same pot from seed to harvest, Fox Farm offers a complete nutrient system that is also formulated for plants like cannabis and goes perfectly with their soil to make sure your plant is getting the right levels of nutrients throughout its life.
Growing in Europe
Canna was started in the early 90s, but their research and development started long before the opening of the company and continues to be a scientific pioneer in growing. They also offer a range of nutrients to help your plant along the way.
CANNA Terra Professional is a nitrogen-rich potting mix designed for fast-growing plants. It contains a blend of high-quality organic ingredients including upgraded black peat, granulated peat moss, and perlite. These ingredients promote exceptional route development and the formation of thicker stems. In turn, this promotes faster metabolism combined with low sickness rates ensuring higher yields. The drainage and water retention capabilities allow one to create the perfect conditions for their plants whether growing indoors or outdoors.
Other good soil options
Kind “Super” Soil (Living Soil)
When cannabis growers talk about “super” soil, they’re usually referring to soil that has been amended with slow-releasing organic nutrient sources, and then composted for several months (learn more about super soil).
The composting process creates a “living” soil that is full of microorganisms in the rhizosphere (the area around the roots). The properly composted soil has nutrient sources that slowly break down over the course of your plant’s lifecycle. It very closely mimics what happens in nature.
Super Soil has a colony of micro-organisms living in the soil which form a symbiotic relationship with your plant roots. They deliver nutrients to your plant, and in return, they eat the sugars that get secreted by your roots! The “micro-herd” in the soil delivers nutrients directly to your plants. As long as you’re using decent water, you usually don’t need to worry about pH or other things that can disrupt nutrient absorption in regular soil.
However, when growing with Super Soil, it’s a good idea to avoid watering too much at a time, as extra runoff water will drain away some of the nutrients. Try to give just enough water to saturate the soil with very little extra coming out the bottom. Since you won’t be adding more nutrients through the grow, you want to conserve what’s in the soil!
Organic Super Soil
This is what kind of soil to get if you don’t have any “good” soil available, but want something that is known to work for growing cannabis.
Generally, anything labeled as an “organic potting mix” will work. This type of mix hasn’t been amended with chemical slow-release nutrients, which is one of the main things you want to avoid with soil for cannabis. I know it sounds like heresy, but even the Miracle-Grow version of “organic potting mix” will work okay, because unlike their original potting mix it doesn’t contain chemical nutrients (though it still has poor drainage and moisture retention – almost any other type of organic potting mix is better!).
Usually, an organic potting mix does not have enough nutrients to last your plants for more than a few weeks, so it’s a good idea to always supplement with cannabis-friendly nutrients, especially in the flowering stage when your plant is making buds and needs lots of extra Phosphorus and Potassium.
Espona Organic Potting Mix is found in many stores in the US, and works for growing cannabis!