If you’re in the business of growing your own green, it’s important to know which type of soil is best for cannabis. The truth is, if you’re not careful, you could end up choosing the wrong soil—leading to serious setbacks in your grow.
Using the right soil is essential because it gives your cannabis plants the nutrients they need to grow big and strong, while also managing moisture, oxygen, microbes, and more.
Choosing the best soil for cannabis comes down to supporting a healthy root system—one that can spread out and absorb as many nutrients as possible. So, what exactly makes good cannabis soil?
Ingredients Found in the Best Cannabis Soil
First things first, let’s go over the ingredients commonly found in quality cannabis-growing soil and the roles they play. Keep in mind—your soil doesn’t need to include all of them, but generally the more it has, the better.
- Sphagnum Peat Moss: This creates a slightly acidic environment that is ideal for nutrient absorption, and it's also ideal for water retention.
- Compost: This is something that's rich in both microbial life and organic matter, therefore improving the amount of nutrients your plants can absorb while also improving soil structure.
- Coco Coir: If you need something that will allow for better aeration and moisture retention without compacting like soil does, then coco coir is a must.
- Perlite: Perlite (or some other form of aeration) is very important to having any good potting mixture for cannabis, because it helps improve both air flow and drainage. It helps prevent compaction and root rot.
- Earthworm Castings: Earthworm castings contain plenty of microbes and nutrients, allowing for better soil fertility and plant growth.
- Bat Guano: Although it might sound like something you don't want in your soil, bat guano is actually very beneficial, as it's loaded to the brim with phosphorus, nitrogen, and many beneficial microbes.
- Fish, Crab, and Bone Meal: Although these are all three separate inputs, in their own ways, they contain respectable amounts of nitrogen, phosphorus, calcium, and trace minerals.
There are several other ingredients you might find in good cannabis soil, such as azomite—a natural mineral additive. Pumice is another, known for improving root aeration and soil drainage. Other useful additions include dolomite lime, kelp, vermiculite, greensand, and mycorrhizae.
Key Qualities to Look for in Cannabis Soil
If you're looking for the best soil for growing cannabis, there are a few specific traits that you want to look out for. In fact, there are five main traits of soil that you want to pay attention to when making a purchase, including the following.
Drainage
First, always look for soil that features good drainage. Soil that doesn't drain properly stays wet for a long time, and this leads to root rot. If the roots are saturated for far too long, they will begin to rot, and this can kill the rest of the plant. Having soil with additives like sandy loam and perlite is therefore essential.
Water Retention
Although it might be odd to discuss water retention right after we talk about drainage, this is important as well. Yes, your cannabis plants require good drainage to prevent the roots from rotting, but your soil mixture also needs to be able to retain a certain amount of water to provide your cannabis plants with a slow and steady release of moisture over a prolonged period of time.
Texture
Many people might not think about this, but the texture of the soil is also important to keep in mind. Cannabis plants prefer a relatively light and airy soil, as this allows for proper nutrient absorption and root growth.
See Also: Why Nutrient Availability Matters More Than Nutrient Quantity
Nutrients
Yet another important factor to pay attention to when choosing the best soil for cannabis growth is the nutritional content of the soil in question. Cannabis plants need a balanced mix of macro nutrients, including nitrogen, phosphorus, and potassium, as well as micronutrients such as sulfur, magnesium, and calcium.
Acidity
Cannabis plants generally prefer a slightly acidic soil, with a pH range of around 6.5 being ideal. If you can find soil that is already pH balanced, then you are on the right track.
Which Soils to Avoid for Cannabis
When growing cannabis, there are certain types of soil you’ll want to avoid, as they are not well-suited for cultivating this particular plant. Below is some key information to keep in mind when selecting the right soil for your grow:
- Avoid any soil that contains large amounts of clay, as it holds excessive moisture and restricts proper aeration, which can hinder root development.
- Stay away from soil with high salt content, as it compacts easily, reduces drainage efficiency, and can eventually suffocate your plants.
- While a small amount of sand or sandy soil can be beneficial, too much is problematic. Sand doesn’t retain nutrients well and offers poor water retention, both of which are essential for healthy cannabis growth.
- Avoid any soil with a pH level outside the 6.0 to 7.0 range. Soil that falls outside this ideal range can lead to nutrient lockout—and in extreme cases, the eventual death of your plants.
Best Store-Bought Soil for Cannabis
Of course, you can always buy regular potting soil and mix in some of the ingredients mentioned above to create your own custom blend. That said, if you don’t have the time or energy for that, purchasing a cannabis-ready soil is the next best option.
Here are some great options to consider:
- Fox Farm Happy Frog Potting Soil
- Fox Farm Ocean Forest Soil
- Fox Farm Coco Loco
- Roots Organics Original Soil
- Purple Cow Organics Indicanja Organic Living Soil
- Coast of Maine Organic Raised Bed Castine Blend
- Coast of Maine Cobscook Blend Garden Soil
- BIO365 BIOFLOWER Soil
Final Thoughts on Choosing the Best Soil for Cannabis
As long as you choose a well-balanced soil that includes natural fertilizers and nutrients—plus the right texture, proper aeration, good drainage, ideal acidity, and reliable water retention—your cannabis plants will thrive and produce great results! A healthy root zone is the foundation of strong, vigorous growth. With the right soil in place, you’ll be setting your plants up for a successful harvest.
