Prepping the soil for an outdoor cannabis garden makes all the difference. Learn about the small details that make a high-quality harvest. If you have an indoor cannabis grow set-up, you need the best soil for growing weed indoors. Our guide dives into what factors to consider and the best ones. What is Good Soil For Growing Cannabis? When it comes to growing cannabis in soil, unless you’re using a brand that is known for making soil that is specifically cannabis-friendly, there are a
Best Soil for an Outdoor Cannabis Garden
Correctly preparing the soil for an outdoor cannabis garden can make all the difference to the quality and size of your eventual harvest. Cannabis has specific requirements in terms of soil quality and texture. Here is a brief guide to ensuring all variables are optimized.
Choosing the best soil for cannabis means monitoring soil acidity, texture and pathogens or pests inherent in soil. Making your own soil or purchasing sterile soil gives you full control over the acidity, nutritional content and texture of the soil. At the same time, planting in the ground exposes cannabis plants to the entire living organism that is soil — and this is very difficult to create in a pot.
In any case, the growing medium is fundamental to the grow itself as well as the final harvest. Having well prepared soil can help a grower mitigate problems throughout the grow. Theoretically, if soil is well nourished, the plant should thrive with little intervention. A healthy plant necessarily starts with great soil, and without the optimum soil for growing cannabis, you will never be able to bring about an optimum harvest.
Soil texture and composition for outdoor soil
The best soil texture for cannabis is light, loamy soil that drain swell but also retains a degree of moisture. Loamy soils are a mixture of sand, silt and clay in an approximately 40:40:20 ratio:
- Sand is a major constituent of many soils, and is characterized by granular particles of rocks and minerals that measure 0.05mm to 2mm in diameter.
- Silt is finer than sand, and consists of particles measuring 0.002mm-0.05mm.
- Clay is finer still, and its particles measure less than 0.002mm in diameter.
One method of determining soil composition involves shaking soil in a jar full of water and allowing the particles to settle; a more detailed explanation can be found here.
The smaller the average particle size in soil, the harder it is for water to travel through it. You can think of it like a coffee machine. If you pack the coffee into the wand too tight, it’s near impossible for the water to come filtering through. By the same principle, sandy soils have very quick water drainage, while soils with high clay content become waterlogged easily.
If you’re using natural local soil, you can mix extra sand, silt or clay into it to improve its soil draining or retaining capabilities as needed. Drainage and soil stability may also be improved by adding gravel, which in technical terms is rock and mineral particles measuring 2m-75mm in diameter. Larger rocks can be removed where possible to avoid causing obstruction to the roots of plants.
If soil is poor, you may wish to consider buying good-quality commercial soil and mixing it into existing soil. You can also add manure, mulch, bloodmeal, bonemeal, or a range of other soil additives designed to improve nutrition release. You can even grow your plants entirely in bought commercial soil, in bags or pots so that they are not exposed to local soil.
Regulating pH of soil for growing outdoors
The optimum pH range for cannabis is between 5.5 and 6.5, making it slightly acidic. If soils are more acidic or alkaline than this, a range of deficiencies or toxicities can result. Soil that is too acidic or too alkaline disturbs a plant’s ability to absorb and use nutrients. If nutrients are not taken up in optimum ratios and quantities, your plants will not achieve the maximum quality and yield, your final harvest will suffer as a result.
Soil pH can be adjusted with a pH regulator. This is usually a solution that can be purchased from any gardening store. The most commonly used ingredient to lower pH (make it more acidic) is sulphur. Sulphur reacts with specialized bacteria commonly found in soil to create sulphuric acid, therefore acidifying the soil.
To increase pH, agricultural lime is usually added to soil. However, it isn’t necessary for cannabis cultivators to purchase sulphur or lime. These are usually available in solution at garden stores. A thorough guide to adjusting pH can be found here.
Remember that before you add a pH regulator to your soil, you first must know the current pH of your soil. This is measured with a soil pH meter. It can also be purchased from your garden store. You should only add pH regulator to your soil once you know the current state of acidity.
How to Choose the Best Outdoor Cannabis Strain
Sterilizing your outdoor soil
Sterilizing your soil by exposing it to steam can kill off many harmful bacteria, fungi and insects, while allowing several beneficial bacteria to remain alive. If purchasing good-quality commercial soil intended for growing cannabis, it is usually unnecessary to sterilize soil. However, if using local, natural soil, it may be helpful to sterilize where possible. It may also bring the added advantage of killing off any unwanted weed seeds present in the soil.
Sterilizing is a difficult and time-consuming process that is often overlooked though. If it’s not feasible to conduct this step, there are other ways to control pests. You can introduce beneficial microbes and insects to soil, as well as organic, plant-based compounds that repel or kill pests without harming the plant.
There are various techniques for sterilizing outdoor soil. Solarization is one method, and involves thoroughly tilling the soil so that it is broken up into fine pieces, watering and covering with a sheet of clear plastic.
The sheet of plastic amplifies the heat and light of the sun and allows the soil to reach high enough temperatures to kill off most undesirable microorganisms. Soil must reach temperatures of 46°C (114°F) for four to six weeks to be fully effective. It should be checked and re-tilled regularly to ensure that temperatures are sufficient and consistent.
If soil solarization is not possible due to time constraints, it may be possible to sterilize your soil by using steam. Large-scale agricultural operations make use of expensive, specialized equipment, but it is possible to use cheaper household sources of steam such as a pressure cooker to sterilize soil.
There are also methods that have been designed for smaller-scale grow operations. For example, the Hoddesdon grid method is a technique that involves layering tilled loam on a steel grid over a shallow pan of constantly-boiling water so that steam can rise through it. When temperatures reach 82-88°C (180-190°F) throughout the soil, sterilization is complete.
Growing outdoors: Pots, bags, or holes in the ground?
When growing outdoors, there are several options available: grow your plants in pots or planters, keep them in growing bags (which may be the plastic sack your commercial soil was purchased in, or may be specially-designed bags that are typically made of hessian or breathable plastic). You can also dig holes in the ground and plant directly into the soil. Outdoor soil can be optimized using the methods outlined above, or use without modification if testing shows it to be naturally optimized for growing cannabis.
If growing in pots or bags, you have the advantage of using commercially-bought soil which is not only optimized for growing cannabis but pre-sterilized to ensure that no harmful microbes are present. The downside is that your plants will be constricted by the size of their container. Pots may also require regular transplants as well as water (which they cannot receive from groundwater as plants in permeable bags or holes in the ground can).
On the other hand, digging holes in the ground and planting your young plants straight into the soil allows them to grow without constraint, and will allow roots to access the maximum amount of groundwater. Thus, they will achieve larger sizes and will require less vigilant maintenance, but may be at increased risk of exposure to soil pathogens and even contamination from agricultural run-off, for example.
Choosing the best soil for cannabis is often not as complicated as growers make it out to be. This is especially true for those who are just beginning to grow cannabis, and are not particularly concerned with yielding specific amounts of specific cannabinoids. Cannabis grows almost everywhere, and is known to grow in wet soil next to riverbeds as well as on rocky mountainsides. Well-nourished soil with the correct texture and pH is the best starting point, after which many adjustments can be made throughout the grow using nutrients and pH regulator.
Watch your plants throughout the grow, and adjust the soil as need be. Growing cannabis is a learning process that requires time and patience, and the best things are learned on the job!
Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.
Best Soil For Growing Weed Indoors
If you have an indoor cannabis grow set-up, you need the best soil for growing weed indoors. Our cannabis soil guide dives deep into the factors to consider when shopping for soil for pot plants including its drainage, water retention, and texture.
In addition, we list our favorite potting soil products for cannabis, so you can grow big and bountiful yields time after time.
Choosing the Best Soil for Indoor Cannabis Gardens
When shopping for the best potting soil for cannabis, there are few factors to consider. First, how many plants are you intending to grow? This will help determine the amount of soil you will need.
Above all, you want soil with plenty of nutrients, proper drainage, and good water retention. Here are some factors to consider when buying the best potting soil for weed.
The best soil for growing weed indoors includes an optimum mixture of silt, sand, and clay soil, known as loamy soil. Ideally, the mix should have about 40% silt, 20% sand, and 40% clay.
Make sure your plants get a loose and light soil texture to help with root growth and ensure oxygen gets to your roots.
Cannabis potting soil requires proper soil drainage. When watered, the soil should not hold the water too much to where it pools on the top. If you have bad drainage, your plants can be vulnerable to root rot and mold.
While you want soil with proper drainage, you also don’t want the water to completely flush through without allowing the roots to take in water and nutrients.
Water retention refers to your soils ability to hold water. The best soil for growing pot indoors has balanced drainage and water retention properties.
PH refers to how alkaline or acidic solution is. Cannabis thrives in a soil pH range between 5.5 and 6.5. Deviating slightly from this range won’t cause too much damage but if it goes well beyond the range, you can get stunted growth, lower yields, and dead plants.
Nutrients are your cannabis plants life force. Most ready-to-use and organic soil mix for weed is packed with nutrients for your cannabis.
Keep in mind, the nutrients in your soil mix don’t last forever. At most, they can last a few weeks and require you to keep a close eye on any nutritional deficiencies or signs of overfeeding.
Best Soil for Growing Weed Indoors
1. FoxFarm Happy Frog Potting Soil
FoxFarm’s Happy Frog Potting Soil is ready-to-use for indoor and outdoor applications. Happy Frog potting soil features soil microbes such as mycorrhizae and humic acid to improve root growth and nutrient uptake.
Other goodies include bat guano, aged forest products, and earthworm castings. Keep in mind, this soil is designed for container planting.
Learn How To Grow Cannabis!
2. FoxFarm Ocean Forest Potting Soil
FoxFarm’s Ocean Forest Potting Soil features a robust blend of ingredients from the “earth and sea.” Its powerful ingredients include fish emulsion, aged forest products, earthworm castings, crab meal, and sphagnum peat moss.
Its sandy loam, aged forest products, and sphagnum peat moss give this soil a properly aerated texture that is sure to improve nutrient uptake. This soil is also designed for container use.
3. Super Soil Organic Concentrate
From Nature’s Living Soil, the Super Soil Original Organic Concentrate comes in a 1, 5, or 10 lb. bag. All you need to do is add your preferred organic potting media to complete your mix. It contains all organic ingredients that your plant will need to thrive.
Full of helpful microorganisms and fungi, this concentrate can produce the best-looking and tasting buds around. Ingredients include organic earthworm castings, bat guano, blood meal, bone meal, azomite, epsom salt, coconut water powder, kelp meal, alfalfa meal, and so much more.
4. FoxFarm Coco Loco Potting Mix
FoxFarm’s Bush Doctor Coco Loco is a coconut coir potting mix meant to recreate the tropical jungle floor. Light and airy, it does this by incorporating layers of exotic coconut palm humus which can hold more than its weight in water while still retaining great drainage characteristics.
Its ability to hold onto water will mean you wont need to water your garden as often. Water every few days for best results.
5. Big Rootz All-Purpose Potting Soil
Big Rootz’s All-Purpose Potting Soil features a professional-grade composition at a budget-friendly price. This cheap soil for growing weed is meant for indoors or outdoor gardens and has been Certified Green Clean (CGC).
A team of weed growers developed this high-quality formula that combines rapid-release amendments with medium and slow release for an optimal performance.
6. Roots Organics Rod Original Potting Soil
Roots Organics Original Potting Soil is ready-to-use for your indoor garden. Its formula is perfectly designed for aeration and water retention so you can feed your plants frequently for fast growth.
Plus, the soil bags can be used as pots. Simply cut off the top, add in your plant, and you’re set. Ingredients include coco fiber, perlite, peat moss, pumice, composted forest material, bat guano, worm castings, fish bone meal, and much more.
There are over 300,000 jobs in the cannabis industry. CTU trained me for one of them!
What is Good Soil For Growing Cannabis?
When it comes to growing cannabis in soil, unless you’re using a brand that is known for making soil that is specifically cannabis-friendly, there are a few things that you need to consider before starting a grow.
What should you look for in good cannabis soil?
I think most growers agree a good cannabis soil should look dark and rich, with a loose texture that drains well and can hold water without getting muddy (you want wet soil, not dirt-batter!). But beyond that, what do you look for?
The following video shows the soil texture you want (this is Coco Loco, an excellent soil for growing cannabis)
Some growers choose an amended and composted “hot” soil that slowly releases nutrients over time. With this type of soil, you typically just add water or natural supplements like worm tea from seed to harvest. Other growers prefer a lighter potting mix so they have more control, and give nutrients in the water once the plant roots have used up the nutrients in the soil. But which brands can you trust?
Some popular soil examples that I’ve used with good results include:
- Almost any organic soil potting mix – If you can’t order special soil online, ask for the best soil at your local gardening store. You can use almost any organic soil potting mix to grow cannabis. I say “organic” because that cuts out a lot of potentially problematic ingredients like slow-release chemical nutrients (which often cause nutrient issues in the flowering stage by delivering too much Nitrogen). If asked what you’re using it for, say tomatoes. You should plan to start adding extra nutrients in the water by the time a plant is a few weeks old as the roots will quickly use up everything. Try to look for soil with a rich and dark but loose texture. It’s a good sign if you see little white pebbles mixed in (this is perlite, which makes soil drain better). If a soil looks like dirt or mud, it’s no good!
- Roots Organics Original – This was the first soil mix I ever used to grow cannabis and I had a great experience. I’ve moved on to Fox Farm products because they were available at my local hydroponics store, and now I’m hooked on Coco Loco. But Roots Organics Original soil has been around for a while because it works great. As with most soil mixes, you will need to supplement plants with additional nutrients after a few weeks.
- Fox Farm Happy Frog soil– This soil mix is relatively light on nutrients so it’s great for seedlings. It’s also suitable if you plan to give nutrients in the water from seed to harvest. If you don’t add extra nutrients, your plants will use everything in the soil up quickly.
- Fox Farm Coco Loco soil– A coco-based soil mix with enough nutrients to last your plants for a few weeks. With Coco Loco, you should start supplementing with extra nutrients once plants are 2-3 weeks old. I personally like Coco Loco the best of any soil mix I’ve used. You can use it by itself and it’s also my favorite base potting mix for a “just add water” super soil grow. I feel like plants tend to grow happy and healthy while being more resistant to over or under-watering compared to the other soil mixes I’ve tried. It’s great soil for other types of crops too.
- Fox Farm Ocean Forest soil– A “hot” soil mix with lots of nutrients packed inside. You can start seedlings directly in this mix though they may show signs of nutrient burn at first until they get adjusted. Ocean Forest has enough nutrients to last your plants quite a while, though you likely should still give extra flowering nutrients once your plants start making buds in order to get the best yields, density, and bud quality. Cannabis plants need a surprisingly lot of nutrients in the flowering stage and you don’t want to starve the plants right as buds are forming.
Recommended soil nutrients:
– These 3 bottles include everything your plants need from seed to harvest. The FF trio produces superb weed with any high-quality soil.
- Learn about other cannabis-friendly nutrients
Important Cannabis Soil Considerations
- Drainage Ability
- Water Retention
Although that list looks vague and complicated at the same time, the requirements you want to meet are actually pretty simple; let me break it down!
Texture, Drainage & Water Retention
It’s easy to get caught up thinking about what nutrients and amendments are in the soil, and those are important, but perhaps the most important aspect of any soil is actually its texture, ability to drain, and overall water “holding” ability.
In order for a cannabis plant to grow and thrive, it needs a good mix of both water and oxygen at the roots at all times! Too much water and the plant roots can’t get enough oxygen (lack of oxygen at the roots is why plants get droopy from overwatering) but on the flip side if there’s not enough water retention the roots can be injured from drying out too quickly!
What gets the best results for growing cannabis is a soil with a light texture that is good at retaining water…but not too much!
Note: Don’t worry, there’ll be examples of good and bad soil in just a bit!
Signs of Good Cannabis Soil
- Appears dark and rich
- Loose texture
- Drains well (doesn’t make a pool on top of your soil for more than a couple of seconds and doesn’t take forever to drain out the bottom)
- Holds water without getting muddy (you want wet soil, not dirt-batter)
Example of “Good” Cannabis Soil Ingredients
Note: You’ll likely never see any soil mix with ALL those ingredients, but I wanted to share examples of common cannabis-friendly ingredients and amendments that often appear on the label of good soil
If you get the soil part right, you have almost everything you need to get to harvest! With the correct texture, drainage and water retention, you’ve got a perfect base. Add good soil cannabis nutrients, especially in the budding phase, and you should get to harvest with great results!
Example of happy marijuana plants in good soil!
More About Common Amendments to Alter Texture, Drainage & Water Retention of Soil
Perlite is one of the most common soil amendments. It is highly recommended for any soil mix that doesn’t have some already.
- Very light, airy white “rocks” that feel almost like popcorn and add oxygen while increasing overall drainage ability.
- Add perlite to the mix (10-40% of the total volume). Use less perlite if you want better water retention and don’t plan on using a lot of extra nutrients. This is because a lot of extra perlite can cause the nutrients leach out faster from the soil. Add higher levels of perlite if you want to use a lot of added nutrients or supplements without burning your plants (since perlite helps prevent nutrient buildup).
Vermiculite “lightens up” heavy soil and improves water retention.
- Some growers use perlite and vermiculite interchangeably, though they’re not exactly the same. Vermiculite holds water much better than perlite, but is not as effective at adding aeration and drainage.
- Some growers use a little bit of both. If you go high with vermiculite, you don’t want to go as high with perlite and vice versa. Together, perlite and vermiculite should never make up more than 50% of your soil!
Coco coir is made from coconut husks. It can be purchased as loose coco coir, in an amended potting mix, or as coco bricks which needs to be rehydrated before use (learn how to re-hydrate coco bricks). Sometimes you’ll find a “soil” mix that is pretty much all coco plus amendments, and these can be a great choice for cannabis. Coco has some unique properties that make it a good supplement for cannabis soil mixtures.
- Coco improves water retention, but doesn’t make soil heavy.
- Roots tend to develop faster and plants are less likely to suffer from overwatering in coco coir.
- Some growers grow in pure coco, but if you’re adding it to a soil mix as an amendment, you might add 10-30% coco coir.
Worm castings is a nice way of saying worm poop, and cannabis plants love it!
- Improves texture, drainage and moisture retention
- Add a natural source of nutrients that breaks down slowly
- Usually contains high levels of beneficial micro-organisms due to going through a worm’s digestive system
- Add up to 30% worm castings in your soil (although it contains nutrients, it’s gentle enough that it’s unlikely to burn your plants even if you add too much)
Now here are a few examples of good and bad cannabis soil so you can see the texture you’re looking for!
Good Cannabis Soil
Rich and light composted soil. Since this soil doesn’t have a lot of perlite, it’s a good choice for a grower who doesn’t want to add a lot of extra nutrients or supplements in the water.
Good Cannabis Soil
Another light, rich soil mix with great drainage. Although there is a wood chip in this picture, for the most part the mix is completely composted and broken down. It’s normal to see some wood pieces in composted soil, but you don’t want to have to wait for a lot of wood to break down while your plants are growing – you want all that rich nutrient goodness to be readily available to your plant roots
Good Cannabis Soil
This soil has quite a bit of perlite, which is a good choice if you plan to feed heavily with nutrients and supplements since the extra perlite prevents nutrient buildup in the soil
Good Cannabis Soil
The plant is growing in organic, composted “super soil” which has enough amendments to last your entire grow, so the only thing you do is add water!
Here’s organic “super” soil up close
Bad Cannabis Soil
This soil is muddy, clumpy and waterlogged. It retains too much moisture, which makes it really easy to overwater your plants.
Bad Cannabis Soil
Cannabis soil should not have a whole lot of big visible wood chips in it. That means the soil hasn’t been fully composted, and all the nutrients and goodness in that wood is mostly unavailable to your plants.
Bad Cannabis Soil
Although this seedling is over a month old, it has stayed tiny. Its growth is stunted by the thick heavy soil that holds way too much water and not enough air. Note how some of the soil looks like one solid object.
Bad Cannabis Soil
Don’t use dirt from outside! It almost never works, especially if it looks like this!
Suggested Brands for Cannabis Soil
Fox Farm Ocean Forest Soil
Fox Farm has been around for over 30 years and makes some of the most common types of “cannabis soil” (at least in the US). They have several great soil mixes, including “Happy Frog” which is a great choice for seedlings and clones.
Their Ocean Forest soil mix is “hotter” soil (higher levels of nutrients) that contains ingredients that cannabis plants love, including earthworm castings, bat guano, fish meal and crab meal. The nutrients contained in the soil will provide everything your plant needs for several weeks. Although it might give young seedlings just a touch of nutrient burn at first, they can be started in Ocean Forest soil and will soon be able to use the nutrients and start growing quickly. Some growers might put a little big of Happy Frog on top of a container of Ocean Forest, just to make it a little more gentle for seedlings the first week or two.
If you are willing to keep transplanting to bigger pots as your plant uses up the nutrients in the soil, you don’t need to supplement with extra nutrients. However, even if you grow in the same pot from seed to harvest, Fox Farm offers a complete nutrient system that is also formulated for plants like cannabis and goes perfectly with their soil to make sure your plant is getting the right levels of nutrients throughout its life.
This plant is growing in Fox Farm Ocean Forest Soil
Kind “Super” Soil (Living Soil)
When cannabis growers talk about “super” soil, they’re usually referring to soil that has been amended with slow-releasing organic nutrient sources, and then composted for several months (learn more about super soil).
The composting process creates a “living” soil that is full of microorganisms in the rhizosphere (area around the roots). Properly composted soil has nutrient sources that slowly break down over the course of your plant’s lifecycle. It very closely mimics what happens in nature.
Super Soil has a colony of micro-organisms living in the soil which form a symbiotic relationship with your plant roots. They deliver nutrients to your plant, and in return they eat the sugars that get secreted by your roots!
The “micro-herd” in the soil delivers nutrients directly to your plants. As long as you’re using decent water, you usually don’t need to worry about pH or other things that can disrupt nutrient absorption in regular soil.
However, when growing with Super Soil, it’s a good idea to avoid watering too much at a time, as extra runoff waterwill drain away some of the nutrinets. Try to give just enough water to saturate the soil with very little extra coming out the bottom. Since you won’t be adding more nutrients through the grow, you want to conserve what’s in the soil!
Nugbuckets is a famous organic soil grower! Check out his plants!
Organic Potting Mix
This is what kind of soil to get if you don’t have any “good” soil available, but want something that is known to work for growing cannabis.
Generally, anything labeled as an “organic potting mix” will work. This type of mix hasn’t been amended with chemical slow-release nutrients, which is one of the main things you want to avoid with soil for cannabis. I know it sounds like heresy, but even the Miracle-Gro version of “organic potting mix” will work okay, because unlike their original potting mix it doesn’t contain chemical nutrients (though it still has poor drainage and moisture retention – almost any other type of organic potting mix is better!).
Usually an organic potting mix does not have enough nutrients to last your plants for more than a few weeks, so it’s a good idea to always supplement with cannabis-friendly nutrients, especially in the flowering stage when your plant is making buds and needs lots of extra Phosphorus and Potassium.
Espona Organic Potting Mix is found in many stores in the US, and works for growing cannabis!
What to Watch Out For With Any Soil Mix At the Store
- Look At and Touch It If You Can! You already have an idea what soil should look and feel like, but here’s a test: If you form the soil into a ball, it should stick together loosely, but it should also easily fall apart again if you squeeze it.
- No “Time Release” Chemical Nutrients in the Soil – These types of soil slowly release nutrients over the course of months, which provides too much Nitrogen in the flowering stage and could possibly impair overall bud growth.
- Soil Should Appear Dark and Rich – Pale, crumbly or sandy soil usually doesn’t have a lot of nutrient content that the plant roots can get to.
- Soil Has Little White Rocks In It (Perlite), if you see white, almost fluffy rocks dispersed through the soil like popcorn, that is usually a good sign because it means this potting mix was intended to have good drainage.
- Soil Isn’t “Heavy” – Cannabis grows best in soil with a light airy texture and great drainage, which may seem almost fluffy when it’s dry.
- Example of “Good” Soil Ingredients – Composted forest humus, sandy loam, sphagnum peat moss, coco coir (sometimes labeled coco fiber), perlite, earthworm castings, bat guano, fish meal, crab meal, bone meal, blood meal, Azomite, pumice, kelp, dolomite lime, mycorrhizae and leonardite. That’s not everything, just examples of cannabis-friendly ingredients you see the most often
- Examples of “Bad” Soil Ingredients – You don’t want to see wood or bark on the label if it doesn’t say it’s been composted first. Also if you see just the word “fertilizer” in the ingredients that’s often code for slow-release chemical nutrients, which you don’t want!
Try to get soil that looks like this!
I hope this soil tutorial helps you find the right soil for your cannabis setup!