When it comes to growing cannabis in soil, it’s imperative to choose or create a blend that will allow your plants to perform at their best. Soil, at a basic level, is defined as the topmost layer of earth in which plants grow, a mixture comprised of organic remains, clay, and rock particles. However, when perfecting an environment for high quality cannabis, there is so much more to consider. Soil varies in a number of common ways, such as:
- pH level
- Water retention
- Nutrient makeup
In this article, we’ll look at what traits make up the best soil for cannabis, tips for building your own soil, and options for pre-mixed soils that will help support a healthy garden.
Traits of Quality Soil for Cannabis
Soil is generally described as having a mixture of sandy, silt, or clay textures. Most of us have gotten our hands dirty before–and while playing in the dirt, you’ve likely noticed these variations. The texture directs the overall structure of the soil, so when it comes time to put your seeds in the ground, be mindful of its attributes.
- Large granular size
- Lower pH
- Pros: Drainage, prevents compaction, easy to work with, and high oxygen levels
- Cons: Poor water retention, dries out quickly, and nutrients get washed away
- Medium granular size
- Pros: Naturally fertile (contains nutrients), retains water, and stabilizes plants
- Cons: Poor drainage and easily compacted
- Small granular size
- Higher pH
- Pros: Provides minerals, retains water, and stabilizes plants
- Cons: Poor drainage, heavy soil, and hard to work with
While some plants thrive in their native soils that are dominated by one of these compositions, cannabis plants are best grown in soil that includes a combination of these three textures and properties. This mixture is known as loam.
- Mixture of sand, silt, and clay
- Near neutral pH
- Pros: Drainage, water retention, naturally fertile, easy to work with, nutrient retention, supports microorganisms, and high oxygen levels
- Cons: Can be costly
What Does Loam Soil Look Like?
The best way to identify loamy soil is by touching it. How does it feel? Sandy soil should be difficult to compact while clay should compact into a tight ball that will not crumble. When squeezed, loamy soils should form a loose ball that will hold its structure momentarily before wanting to break apart in large chunks.
Most potting soils used in gardening will be loam soils. If you’ve ever worked with potting soil, you’ll remember its composition looked rich and diverse, and the color appeared dark and hearty. Beyond texture and color, the soil should smell alive and rich.
Buying the Right Soil for Cannabis
While shopping for soil, you will surely be overwhelmed by the options available at your local garden store. You now know most of these soils will be loamy by definition, but then why are there so many different types? Consider the soil type as the basic structure for your soil. From there, look at nutrients, microorganisms, and other amendments that improve your soil. Your choices will be flooded with words like:
- Worm castings
- Bat guano
- Peat Moss
- Fish Meal
- Bone Meal
- Glacier rock dust
- Plant food
These are just a few examples of amendments that are commonly listed on different types of soils. Heavily amended soils will have long lists that break down all organic nutrients. Meanwhile, some companies create soils that offer great structure with base nutrients, but allow you to fill in the gaps as you desire.
For most first-time gardeners, I recommend buying a quality potting soil that will provide your plants with enough nutrients to get them through most of their growth cycle without having to add many amendments and liquid nutrients. Below are two soils I would recommend to beginner cultivators.
Recommended Soils for Cannabis
Depending on where you live, you’ll have a different experience finding a quality soil mix that fits your needs. Generally speaking, my advice is to visit your local nursery or grow store and talk to the experts. If you’re shy about mentioning cannabis, ask for a rich soil suitable for tomatoes, which thrive in similar soil.
It also should be noted that the soils below are not recommended for starting your plants. Ready-to-grow soils contain lots of organic nutrients that are too rich for a seedling. These soils are made so that you can transfer starts, but seedlings should be grown in a simpler potting soil.
Red’s Premium Biochar-Based Soil
Produced in Colorado by Miller Soils, Red’s premium blend is your one-stop shop for growing cannabis. This soil is ready to plant, containing their most complex mixture of amendments. The biochar provides a quality habitat for the microbes to populate while aiding water and nutrient retention. This blend is designed to hit the ground running with a complex food web already active in the soil, waiting for your roots to enjoy.
While not yet readily available to the public, this soil will be making its way into every major city on the West Coast by April. When using a soil like Red’s, you don’t need to worry about feeding your plants more than a few times, if at all.
Roots Organics 707
A notable soil produced by Aurora Innovations, the Roots Formula 707organic blend offers a different approach to read- to-pot soil. It was designed to aid in water retention with a peat moss base, while backing off on amendments so that you can topsoil or liquid-feed your plants at your own discretion. It is recommended that you wait 10-14 days before you begin to feed your plants growing in Formula 707.
Designed for large-scale outdoor growing, Formula 707 is widely available and suitable for indoor gardens as well.