What’s the best soil for growing marijuana?

Trevor Hennings June 29, 2020

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When it comes to growing cannabis in soil, it’s imperative to choose or create a blend that will allow your plants to perform 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.

But when perfecting an environment for high-quality cannabis, there is much to consider. Soil varies in a number of common ways, such as:

pH level
Water retention
Texture
Nutrient makeup
Drainage

In this article, we’ll look at what traits make up the best soil for cannabis to help support a healthy garden.

Check out these additional resources on soil and planting:

Traits of quality soil for cannabis

Soil is generally described as having a mixture of sandy, silt, or clay textures. The texture directs the overall structure of the soil, so when it comes time to put your cannabis seeds in the ground, be mindful of its attributes.

Sandy soils

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Large granular size
Low pH
Pros: Good drainage, prevents compaction, easy to work with, high oxygen levels
Cons: Poor water retention, dries out quickly, nutrients get washed away

Silt soils

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Medium granular size
Pros: Naturally fertile (contains nutrients), retains water, stabilizes plants
Cons: Poor drainage and easily compacted

Clay soils

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Small granular size
High pH
Pros: Provides minerals, retains water, stabilizes plants
Cons: Poor drainage, heavy soil, hard to work with

Loam soils

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While some plants thrive in their native soils, which are dominated by one of the compositions listed above, cannabis plants are best grown in soil that includes a combination of those three textures and properties. This mixture is known as loam.

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 won’t crumble. When squeezed, loamy soils should form a loose ball that will hold its structure momentarily before breaking apart in large chunks.

Here are some qualities of loam soil:

Mixture of sand, silt, and clay
Near neutral pH
Pros: Drainage, water retention, naturally fertile, easy to work with, nutrient retention, supports microorganisms, high oxygen levels
Cons: Can be costly

Most potting soils used in gardening are loam soils. If you’ve ever worked with potting soil, you’ll know that its composition is rich and diverse, and it looks dark and hearty. Beyond texture and color, the soil should smell rich and alive.

Buying the right soil for cannabis

While shopping for soil, you might be overwhelmed by the options available at your local garden store. You now know that most of these soils will be loamy, but why are there so many different types?

Consider the soil type as the basic structure of your soil. From there, look at nutrients, microorganisms, and other amendments that improve your soil. Your choices will be flooded with words like:

Perlite
Worm castings
Bat guano
Biochar
Peat moss
Compost
Fish meal
Bone meal
Glacier rock dust
Plant food

These are just some 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 they contain. Some companies create soils that offer a great structure with base nutrients, but allow you to fill in the gaps as you desire.

For most first-time gardeners, we 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 or liquid nutrients.

This post was originally published on January 10, 2018. It was most recently updated on June 29, 2020.