What Is the Best Potting Soil For Marijuana?
Article written by
Homegrown Cannabis Co.American Seed Bank and Cultivation Experts
Content reviewed by
Dr. Lewis JasseyMedical Director - Pediatric Medicine
The best potting soil for marijuana contains a wealth of textures, nutrients, amendments, and organic life to keep the roots happy and healthy. It forgives mistakes and makes your buds fat and flavorful.
Using suitable soil is vital, but choosing it can be tricky. Keep reading to learn about the significance of soil quality and what makes a substrate fit for weed. We also share our seven favorite store-bought potting mixes.
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Why Soil Quality Matters
Soil houses a plant’s roots, provides structural support to plants, and acts as a water and nutrient source. It’s the primary environment for your garden and must be in good shape to produce top-tier buds.
Quality soil means healthy growth. Here’s what happens when it’s inadequate:
- When it’s too thick, the roots choke and can’t expand. This issue results in slow and stunted growth.
- When it’s too loose, water drains before the root system absorbs it. Underwatering symptoms and nutrient deficiencies ensue.
- When it’s too acidic or alkaline, specific minerals get locked out and become unavailable to plants. Again, nutrient deficiencies follow.
- When it’s over or under-fertilized, plants consume inadequate or excessive amounts of essential nutrients. This problem leads to a deficiency or burn.
To correct these issues, you can treat a substrate with pH-Up and pH-Down solutions, additional nutrients, water, or amendments. It’s better to begin with a high-quality medium and nip trouble in the bud, though. Let’s see what factors make up the best soil mix for marijuana.
Choosing the Best Soil for Marijuana
The best potting soil for marijuana is dark, rich, loose enough to drain well, and retains water without looking muddy. Gardening stores mix several types of soil and amendments to make that happen.
Natural soils come in these four categories:
- Sandy soil: Easily permeable for root growth but doesn’t retain water and fertilizer well.
- Clay soil: Rich in minerals and natural nutrients but dense and with poor drainage.
- Silt soil: Lots of minerals and good water retention, but can form a crust in hot weather.
- Loamy soil: A blend of the former three, bringing together the best qualities of different soil types.
All cannabis soils share some common traits, and understanding them helps you pick the best option.
Texture
“Sandy,” “silty,” and “loamy” describe how the soil feels.
The texture depends on soil particle sizes and affects how much water and air it can hold. For example, clay particles bind together when wet and become challenging to work with. Sand is very loose and may slip through your fingers.
The ideal soil texture for cannabis is light and somewhat loose to promote root development and oxygen consumption. Think loam with 40% sand, 40% silt, and 20% clay.
pH Value
The pH level indicates how acidic or alkaline something is. Since cannabis can only absorb nutrients in slightly acidic environments, this figure is essential for maintaining plant health.
Soil for weed plants should have a pH of 5.8-6.2. Organic growing conditions allow more variation because the microbial life buffers the root zone.
Drainage Ability
Drainage describes the rate at which water exits the soil through runoff. In simple terms, the time it takes to disappear from the soil surface and reach the tray.
Cannabis plants require soil with good drainage. When you shower them, the liquid shouldn’t pool on top but run to the roots. Sandy soils drain rapidly, while clay retains plenty of moisture.
Water Retention
Water retention is the opposite of drainage, describing a medium’s ability to hold moisture. The right soil for weed uses a blend of well-drained and water-retaining elements to harmonize these two factors.
Nutrients
Weed plants draw minerals from the soil to grow and thrive. Most natural environments contain some elements for growing marijuana, but these aren’t enough to get sticky buds. You have two options here.
One is to supplement with liquid nutrients. Buy the highest-quality fertilizers, dissolve them in water, and feed your weed according to the manufacturer’s instructions.
The other is to amend your soil with organic substances and introduce microorganisms that turn them into plant food. Use compost, bat guano, humus, worm castings, or another natural source.
Amendments
Amendments make your medium suitable for weed. Store-bought potting mixes already contain these additional elements, but you can also add them to natural soil. Excellent options include:
- Coco coir: Light coconut husk fibers improve your medium’s drainage and water retention abilities.
- Perlite: Light white rocks that aerate the soil (let oxygen reach the roots) and improve drainage capacity.
- Vermiculite: This heat-treated mineral makes the soil lighter and increases moisture retention.
- Clay pebbles: These small rocks assist with drainage and protect the roots from rot. They might also reduce evaporation rates and shelter the beneficial microbes.
Living or Not?
When there’s microbial life in the soil, bacteria break down organic material into plant food. We call substrates with this ability “living.”
Living soil is ideal for organic growing. Microorganisms form symbiotic relationships with weed and produce high yields of all-natural buds. They also reduce the requirement for a strict feeding schedule and make plants more resistant to stress and disease.
Such soil life can give rise to fungus gnats and other insects, so watch out for pests in organic gardens. This option generally requires more TLC than “cleaner” alternatives, too. Skip it if you’re brand new to cultivation.
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7 Best Store-Bought Soils for Cannabis
You could use the information above to find and buy high-quality soil for your garden, but we did the legwork for you and devised this list of the best organic soil blends for cannabis cultivation.
Expert tip: Combine the best soil with the highest-quality cannabis seed genetics for a prosperous gardening journey. Visit our partner Homegrown Cannabis Co. to get started.
1. FoxFarm: Ocean Forest Potting Soil Mix
Ocean Forest potting soil by FoxFarm consists of sandy loam with hints of silt and clay for better drainage. It contains fish and crab meals, moss, earthworm castings, forest humus, and bat guano to mimic the top naturally-occurring soils.
The pH is 6.3-6.8, enabling fertilizer uptake for rapid growth. This soil contains everything seedlings need, but the manufacturer suggests additional feeding in the vegetative and flowering stages.
Ocean Forest has barely any downsides. While a bit costlier than alternatives, it eliminates the need for fertilizer for at least 30 days. If your climate is hot and humid, consider amending it with perlite to avoid moisture issues.
2. Roots Organics: Original Potting Soil
Original potting soil by Roots Organics consists of perlite, coco fiber, and peat moss, three materials for prolific plant growth. It also features composted forest material, kelp, fishbone, alfalfa meal, worm castings, and bat guano as food sources.
This potting soil contains beneficial mycorrhizal fungi to enhance nutrient uptake and help plants resist stress. As such, it’s a good option for fast-growing autoflowers and first-time cultivators.
The pH is 5.5-6.5, suiting most strains. Given its composition, you can use it in isolation or combine it with your existing soil for the best results.
The rich life of this soil mix is also its dominant downside. The amount of organic matter makes it a breeding ground for fungus gnats, so implement pest-protection practices from day one.
3. Brut: Super Soil
Super soil by Brut is a dark soil blend loaded with bacteria and enzymes. Its peat moss contents enable excellent water retention. On the organic side, it has worm castings, composted cow manure, and kelp.
This super soil is a concentrate to be mixed with organic soil. Once you do, it takes care of plants’ water and mineral requirements and reduces the need to feed and shower your garden. As a bonus, it’s completely non-toxic and odor-free, creating a sustainable garden.
According to growers, this mixture has a pH of 5.5. The microbes buffer the roots from imbalances, and the acidity balances out when combined with soil.
4. The Soil King: Big Rootz
Big Rootz by The Soil King is a certified organic all-purpose potting soil. It consists of peat moss and triple-washed coco coir for optimized retention and drainage. The blend has compost and worm castings to feed cannabis plants.
This blend for growing marijuana is pH-optimized, eliminating the risk of a nutrient lockout. Additional feeding becomes necessary only in late vegging, removing one concern from your task list.
The Big Rootz product is susceptible to pest infestations. It’s also too rich for seedlings, so you need a different potting mix for seed germination. The company also stocks a Baby Rootz blend for this purpose.
5. Mother Earth: Terracraft Potting Soil
Terracraft potting soil by Mother Earth consists of peat moss, perlite, and processed forest fertilizer, retaining more moisture than regular soil. For this reason, water consumption is lower when you use it. It uses seabird guano, bat guano, and earthworm castings as fertilizers.
Growing weed is straightforward with this soil since it’s pH-balanced and buffered against fluctuations. It’s also dry and fluffy to the touch, making it easy to pack the pot.
Terracraft is suitable for all strains and mimics the simplicity of traditional soil growing. It’s reusable and requires feeding only in flowering.
6. Espoma: All-Purpose Garden Soil
All-purpose garden soil by Espoma is a living blend consisting of peat moss, composted forest products, and limestone as a base. It’s rich in alfalfa, kelp, feather meal, yucca extract, and earthworm castings, which act as fertilizers.
Ectomycorrhizal fungi are an active ingredient in this potting mix and feed marijuana plants. As such, the solution isn’t susceptible to deficiencies.
This blend isn’t ideal as your sole substrate. The manufacturer suggests combining it with natural soil, ideally a loamy variety. Epsoma’s products are at 5.5-7.5 pH, so you might need to reduce the alkalinity.
7. Sun Gro: Black Gold
The Black Gold line by Sun Gro is a cannabis grower’s friend. The brand’s all-purpose potting mix consists of peat moss, compost, aged bark, perlite, and earthworm castings and feels like regular soil. It offers outstanding moisture retention and drainage and continually feeds plants.
The blend is semi-hoarse, leaving enough air for prolific root expansion. According to the manufacturer, it may feed plants for up to six months. Since cannabis is hungry, we say it’s better to start supplementing in mid-vegging.
The latest version of this product uses Multicote granules for continuous nutrient release. It ensures the plant never lacks minerals or drowns in them.
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Frequently Asked Questions
Can you make your own soil for growing cannabis?
Besides buying it in gardening stores, you can mix up a batch of good cannabis soil at home. If planning to feed your plants with a soluble fertilizer, combine 40% sand, 40% silt, and 20% clay. That way, you get a balanced blend of different-sized particles. You might also consider making super soil at home. Here’s what you need:
- Organic potting soil
- Earthworm castings
- Bone meal
- Blood meal
- Bat guano
- Rock phosphate
- Dolomite lime
- Epsom salts
- Azomite
- Powdered humic acid
Is soil the same as fertilizer?
Soil is not the same as fertilizer. Soil is a growing medium that provides structural support, food, moisture, and protection to the roots. Fertilizer is a substance or material added to soil to promote plant growth. It can be liquid, solid, organic, or chemical in nature.
Do you need different types of soil for different growth stages?
Choose the best soil for growing cannabis, and you don’t have to switch it up between growth stages. Theoretically, you might use sandy substrates for seedlings and loamy ones for vegging and flowering.
The roots are underdeveloped in the earliest stage, so the requirement for water is lower, so sand is a perfect fit. Plants get hungry in vegging and perform better in loam, especially when it contains a nutrient-rich amendment like volcanic rock dust.