What’s the best soil for growing marijuana?
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
- Nutrient makeup
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.
- 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
- Medium granular size
- Pros: Naturally fertile (contains nutrients), retains water, stabilizes plants
- Cons: Poor drainage and easily compacted
- Small granular size
- High pH
- Pros: Provides minerals, retains water, stabilizes plants
- Cons: Poor drainage, heavy soil, hard to work with
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:
- Worm castings
- Bat guano
- Peat moss
- 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.
Having the proper soil is important to growing a strong and healthy cannabis plant. Learn what types of soil are out there and what to look for with cannabis.
How to Grow Cannabis in Soil
First-time growers often start by growing cannabis in soil. If you’ve grown other plants in soil and/or have maintained a soil garden, this may be the best choice for you because you will already be familiar with a lot of what you need to understand to grow cannabis in soil.
Avoid Miracle-Gro! Do not use “Miracle-Gro” soil or any soil that has “extended-release” nutrients for growing cannabis. These types of soil will continue to release nitrogen to your plant roots for up to 6 months. This can cause deficiencies or burn your cannabis plants in the flowering/budding stage, reducing your overall yields. I have seen growers successively grow cannabis in Miracle-Gro, but many of them struggled with nutrient problems in the flowering stage.
Soil Pros for Growing Cannabis
Many Already Have Soil Experience – Growing cannabis in soil is similar to growing plants like tomatoes or corn – soil growing may be the most intuitive option for you, especially if you already have gardening experience.
Simple – hand-water your plants in containers
Outdoor Growing – most outdoor growers choose to grow with soil. In the wild, cannabis grows in soil, so growing outdoors in soil is most like a cannabis plant’s natural environment. Many people find that when growing cannabis outdoors, soil is the simplest and most intuitive way to grow. Growing with composted “super soil” gives the grower the ability to grow outside without needing to add synthetic bottled nutrients or manage the pH of the soil.
Option 1: Store-Bought Soil + Nutrients – Growers can buy soil online or at a store, and simply add nutrients throughout their grow while watering for thriving, happy cannabis plants.
Option 2: Compost or Purchase “Super Soil” – For those who don’t want to worry about soil pH or adding nutrients throughout the grow, there is the option of amending and composting your own super soil (or buying it already composted) specifically made for cannabis plants. While this option takes more time before you start growing, it can be somewhat simpler especially for those who have composted soil in the past.
Note: Some growers believe growing in organic composted super soil with a rich microbial life can actually improve the taste and smell of cannabis by causing a plant to produce higher levels of terpenes and terpenoids.
Soil Cons for Growing Cannabis
Pests – Soil is an organic material, and there are many types of bugs that can live in soil. Often, soil-growers seem to suffer more often from pests attacking their plants than hydroponic growers.
Slower Growth – Growing in soil is not as fast as growing in a soilless or hydroponic setup – hydroponic plants tend to get better growth rates, especially in the vegetative stage.
Get Soil and a Container for Your Cannabis Plants
- Common cannabis soil mixes include Fox Farms Happy Frog and Fox Farms Ocean Forest. Any high-quality organic soil mix will do in a pinch.
- Avoid Miracle-Gro soil or anything with “extended-release” nutrients!
- To improve drainage, it can be beneficial to add 30% perlite to aerate and loosen soil.
- Common cannabis containers include classic plastic pots, terracotta pots, smart pots (fabric pots) and air-pots. Learn more about different types of containers
Soil growing probably requires the least effort of any growing method (especially if growing in super soil). Your main effort will be spent watering your plants.
Not sure which soil should you start with? I recommend starting with Fox Farms Happy Frog soil and mixing the soil with about 30-40% perlite for a perfect cannabis soil starting mix. For the easiest soil growing, get a smart pot (a growing container made out of fabric – they work perfectly for growing cannabis).
Don’t want to use nutrients? Learn how to mix up your own super soil so it has all the nutrients your cannabis plants will need! Bonus: With composted super soil made using the recipe in the link above, you don’t need to worry about maintaining your pH! your super soil will automatically manage the pH for you.
Maintenance Cost – After setup, the main maintenance will be replacing your soil every grow (highly recommended – reused soil often does not get great results even with added nutrients). Occasionally you will have to replace used containers that crack or break. You also need to think about the cost of electricity and replacing nutrients every few grows.
Maintenance Effort – Watering your plants, providing nutrients and managing the pH to prevent deficiencies (composted super soil has microorganisms in it to help manage pH and make nutrients available to your plant roots).
How long until harvest? Soil has relatively slower growth rates than hydroponic methods, but a tuned-in soil grow can achieve impressive growth rates if given a great environment and plenty of bright light. Most soil grows require 1-3 months of vegetative time (depending on how big you want your plants) plus 2-3 months of flowering/budding (depending on your strain).
Many growers feel that cannabis grown in organic super soil has the best smell/taste profile, though this is highly disputed among hydroponic growers 🙂
How long can grower be away? It’s important for a grower to always remain close by for their first grow, especially for inexperienced growers. Experienced growers can safely spend more time away from the garden.
Bigger containers hold more water and therefore give growers more time away, since constant watering isn’t needed. In the best-case scenario, it is always best to check on your plants at least once a day. You never know when a pest infestation will take hold, a plant will fall over, or some other unexpected event will happen.
Most Common Soil Mistake: Overwatering
The most common mistake made by beginners growing cannabis in soil is they water their plants too often. Overwatering is almost never a case of giving your plants too much water at once. Instead, overwatering cannabis in soil is almost always caused by giving the plant water too often.
How to water cannabis plants in soil
Wait until the top of your soil feels dry up to your first knuckle (about an inch deep)
Add nutrients to your water (if needed), then adjust the pH. The most common reason growers get nutrient deficiencies is because they don’t adjust the pH of their water. Most soil growers only add nutrients every other watering (or even less often), but even when giving just plain water you still need to adjust the pH of your water to prevent deficiencies.
Start watering your plants and continue to add water until you see at least 20% extra runoff water drain out the bottom of your pot. Go back to step 1.
Cannabis-Friendly Soil Nutrient Suggestions
For new nutrients you haven’t grown with before, always start at half-strength and raise the amount slowly. Do not use nutrients with every watering! Most growers will add nutrients every other watering or even less frequently. Remember, a little bit goes a long way. You can always add more nutrients later, but it’s a lot more difficult to take them back from the soil.
An easy and simple nutrient system for beginning cannabis soil growers is the Fox Farms Nutrient Trio for Soil.
The Fox Farms trio works great for growing any cannabis strain, without needing any additional supplements.
There are three different bottles that you will need to grow cannabis, “Grow Big,” “Big Bloom,” and “Tiger Bloom.” They are often sold together. Simply follow the included nutrient schedule (here’s a PDF, here’s a JPG) from Fox Farms.
Be aware there is a soil version because Fox Farms offers a hydroponic version of the same nutrient line. Though in my experience the hydroponic version also works just as well in soil 🙂
Nutrient Picks for Growing in Soil
HydroOrganics Earth Juice Nutrients (Grow, Bloom) with the following supplements: Earth Juice Catalyst, Meta-K, MicroBlast & Hygrozyme (use as needed for roots)
This nutrient schedule was used to grow the following buds under a 250W LED.
Don’t Use Miracle-Gro or Other “Slow Release” Soils!
Say “No” to Miracle-Gro soil for growing cannabis!
Many of us have seen Miracle-Gro used around our homes, so we know that it works for ‘regular houseplants’. Cannabis is just a tough weed, so Miracle-Gro nutrients should work great for it, too… right?
No. Not really. Well kinda.
Standard Miracle-Gro nutrients (their all-purpose plant food) will work “just okay” for the vegetative stage of your plant’s growth, but anything with Miracle-Gro in it is a terrible choice for the flowering stage due to its high levels of Nitrogen. Using standard Miracle-Gro nutrients in the flowering stage will cause your buds to grow smaller than they could have, and they may possibly have a chemical taste from nutrient buildup in the plant tissue.
However, the real problem is Miracle-Gro’s “time-released” soil (or any type of extended-release spikes or soils that aren’t organic) which slowly release Miracle-Gro nutrients over the course of several months. These types of soil continue providing Nitrogen slowly throughout your plant’s life. That means your plant won’t be able to use up all the Nitrogen in the vegetative stage as it would with regular soil, again giving you the problem of too much Nitrogen in the flowering stage.
Basically, avoid giving your plants a lot of Nitrogen in the flowering stage! Anything that does that is not a good idea 🙂
General overview of soil growing. Get the pros and cons!