Cannabis cultivators can go back and forth for hours on optimal grow room practices, and the best soil for growing marijuana is a popular debate. But with a wide variety of growth methods available – and fluctuating factors like climate, season, or strain type to consider – there’s no single right answer when it comes to planting cannabis seeds in soil.
However, there definitely are best options for soil mix to keep in mind, depending on how, where, and when you’re growing your cannabis.
The first thing you’ll want to do is consider your environment, look into which types of soil thrive best in that scene, and eventually branch your growing plan out from there.
Cannabis soil factors to consider
If you have a green thumb, you might be aware of the fact that different soil profiles work for different plants – and when thinking about the best soil for cannabis, there are a few factors you’ll want to keep in mind if you want your crop to thrive.
Of course, your cannabis soil preferences will vary depending on how you’re growing your greens (indoor, outdoor, greenhoused, hydroponically, etc.), and things like climate, season, and light exposure will also play a role in this determination.
However, these are some general soil factors to think about (and tailor to your growing environment as needed):
Drainage
If you grow cannabis, you probably know that cannabis plants grow fast – and they tend to be thirsty little guys. However, cannabis roots also require a good amount of oxygen, so acquiring drainage that has an optimal water-air ratio is essential.
Once you’ve picked your growing medium, make sure you select a container that allows for proper aeration and nutrient delivery – and, of course, holes for good drainage flow.
Nutrients
No matter what cultivation method you’ve opted for, cannabis nutrients are essential for healthy plant growth.
This can be a tricky process, because when you release nutrients, you can render your plants extra vulnerable to deficiencies or pests. Nutrients can also be costly and difficult to apply – but once you figure out the right balance, your plants will definitely show you how much they appreciate the extra TLC.
Different nutrients will be required for plant health at different stages of the growth process, but in general, you’ll want to opt for NPK: nitrogen (which can be found in blood meal), phosphorus (which can be found in bone meal), and potassium (which is often found in peat moss or bat guano).
pH Level
Cannabis growers also need to keep their plants’ pH levels in mind, as an imbalance can seriously diminish yields.
For cannabis plants, good soil will sit at around 6.0, but in general, any pH within the 5.8-6.3 range will be okay. Just be careful and keep a watchful eye: if you’re far off the mark, your plants will suffer.
Texture
If you want to grow marijuana successfully, soil texture is another important thing to keep an eye on.
Cannabis plants prefer loose, light soil, as this promotes root development, delivers more oxygen to the roots, and generally helps support that drainage sweet spot you want to stay in.
Water Retention
Watering cannabis plants on a consistent basis is essential for optimal growth. The average plant will require about 3-6 gallons of water per day – and that varies depending on its size, strain, and grow medium.
Because of this, you’ll want to ensure you’re working with soil that retains water well…without forgetting about that need for a healthy amount of drainage.
Cannabis soil amendment options
Rather than relying on store-bought potting mixes, many cannabis growers opt for natural soil as their primary grow medium. And this is perfectly fine – but on its own, it won’t help you grow the best cannabis plants.
When using natural soil, most growers will work in organic matter – or a “soil amendment” – to improve soil texture, drainage, and other factors that might not be optimal for cannabis plant growth. This essentially boosts your natural soil into super soil, giving your plants the best possible odds as they move through the growth stages.
These are some of the most popular options:
Clay pebbles
Expanded clay pebbles are commonly used in hydroponic grow spaces. They contain high amounts of iron, and are good at retaining moisture while still allowing for a consistent flood and drain cycle.
Coco coir
Coco coir is a popular choice for soil amendment, and is most often utilized during vegetative and flowering stages of growth. Environmentally friendly and made from coconut husks, it’s known for promoting fast, healthy root development.
Perlite
A naturally-occurring volcanic glass-water mix, perlite is utilized in grow rooms and outdoor gardens alike. It comes with quite a few advantages for your soil, like enhanced drainage, improved aeration, and pH balancing properties.
Worm castings
Worm castings are another popular soil amendment option: increasingly recognized for improving flower size, terpene and cannabinoid quality, and overall output. They’re also great for warding off plant diseases and pests.
Vermiculite
Vermiculite is a mineral that expands with heat, and it’s often utilized by cannabis growers – particularly for hydroponics. It’s great at retaining moisture and fighting root rot.
Potting soil vs living soil
Potting soil and natural or “living” soil are both used by cannabis growers – your choice will just depend on your growing environment and method, and what works best for the strains you’re working with.
Going with potting soil – a.k.a., pre-made mixes you can buy at Home Depot – is a good option for new growers, or those who are pressed for time or resources.
If you’re going with this approach, check out some of the most popular potting mixes on the market:
- FoxFarm Ocean Forest Potting Soil
Recognized by growers as one of the easiest mixes to use at any stage of plant growth.
- Black Gold Organic Potting Soil
Somewhat pricey, but known for consistent results.
- Canna Terra Professional
A pure mix known for good drainage.
- Top Crop Complete Mix
Supports healthy root development.
- Biobizz All Mix
A good option, but can have inconsistent texture.
- Compressed Organic Potting Soil
Ideal for clones and known amongst growers for having an optimal texture.
Living soil recipe
Interested in making your own super soil mix for success? This process is admittedly somewhat complex, but if you are passionate about growing cannabis naturally and have the patience for trial and error, it’s definitely worth a try.
This is our favorite recipe, but before we get into the details, let’s talk through some major things to note about making your own living soil.
Beneficial microorganisms are the leading ladies of successful soil, and can also improve yield potential. Good living soil will host a thriving microbe community, including things like beneficial bacteria and fungi, archaea, protozoa, and more.
You’ll also want to incorporate some of the aforementioned soil amendments – and get yourself on a consistent cycle of nutrient delivery to ensure your soil is performing its very best for you.
There are quite a few different recipes for living soil mix you can follow, but we recommend beginning with this tried-and-true, incredibly popular approach.
Ingredients
- 14 cubic feet of potting soil
- 1 cubic foot of worm castings
- 2.5 pounds of bone meal
- 2.5 pounds of fish bone meal
- 5 pounds of high phosphorus bat guano
- 5 pounds of blood meal
- 3 cups of oyster shell
- 3 cups of kelp meal
- 3 cups of alfalfa meal
- ¾ cup of Epsom salts
- 1 cup of agricultural lime
- 2 cups of Azomite
- 2 tablespoons of granular humic acid
- 2 tablespoons of compost tea mix
Directions
- Mix all of the ingredients together, adding water if needed to obtain a slightly moist consistency.
- Once thoroughly mixed, transfer your mixture to several covered containers (like totes or covered garbage cans).
- Allow your mixture to “cook” for 45-90 days of compost time.
- Once your mixture has thoroughly composted, fill your planting containers about halfway, adding an inch or two of the base mix on top.
- Then, transplant into the final nursing pot, and finish it off with some more base mix.
- Once that’s done, you can simply amend it with compost tea mix until it’s time to harvest.
Making your own living soil mix is definitely a labor of love, but if this is an approach you’re interested in, go for it. You might have just unlocked your favorite approach to cannabis growing yet.
