Choosing The Best Soil For Cannabis: A Home Grower’s Guide
Growing cannabis in soil is a great way to crop fat, flavoursome buds. Moreover, soil is one of the most forgiving substrates. What are the best soils for growing cannabis? What do you need to know if you want to make your own soil? Our guide answers these questions and more!
Home grower’s guide to the best soil for cannabis.
When growing cannabis, using the right soil is crucial. Unfortunately, sourcing the best soil isn’t always straightforward. From cannabis-specific soils to bargain universal substrates and pre-fertilised types, the sheer amount of options can be overwhelming to novices. And what if you want to make your own soil from scratch?
Let’s talk about the best soil for growing cannabis.
WHAT’S THE BEST SOIL FOR GROWING WEED?
Not every soil is suitable for growing cannabis, and not all cannabis requires the same type of soil. Picking the optimal soil depends on the type of cannabis you’re growing, your climate, whether you’re growing at home or in the wild, etc.
Aside from these factors, there are some common traits among all cannabis soils. Let’s take a look at them:
Cannabis prefers a light and loose soil texture. A light texture promotes root development, and it ensures more oxygen reaches the roots for optimal growth and health.
• Drainage ability
Cannabis soil needs to have excellent drainage. When you water your plants, it shouldn’t pool on top of the soil. If the soil has poor drainage, your plants will get sick and turn out subpar yields, or die.
• Water retention
Just as important as good drainage is water retention, which is the soil’s ability to hold water. Good cannabis soil has an optimal balance of water retention and drainage.
• pH value
pH is a chemical scale that indicates how acidic or alkaline something is. This is important, as cannabis only does well within a small pH range. A good soil for weed has a pH of about 6.0. A pH of 5.8–6.3 will be fine, but if it fluctuates too far outside of this range, you will get diminished yields. If the pH is seriously off, your plants will die.
Cannabis soil needs to contain nutrients so your plants can grow. Fortunately, almost all soils you can buy already feature them. Know, however, that these nutrients will often last only 3–4 weeks. Around the time your plants start to flower, the nutrients in commercial soils will likely be depleted. This is when you should begin to add nutrients.
If you’re growing without additional nutrients, your soil needs to contain organic substances such as humus, compost, worm castings, guano, etc. Microorganisms in the soil will turn these substances into nutrients for your plants to access on demand.
TRAITS OF QUALITY CANNABIS SOIL
If you’re using store-bought potting mixes, these are already optimally “tuned” for growing. Different story if you’re growing organically, though. Natural soil comes in four varieties: sandy, silty, loamy, and clay. But know that most soils consist of varying ratios of these soil types.
For example, a soil may be clay and loamy, or sandy and silty.
Sandy soil is coarse with good drainage, but has poor water retention. When watered, nutrients such as nitrogen will also quickly get washed away. Sandy soil is easy to work with and is a viable choice for cannabis growers.
• Coarse structure
• Low pH
• Pros: Good drainage, keeps soil airy, high oxygen levels, easy to work with
• Cons: Poor water retention, needs frequent watering
Silty soil is a medium-coarse soil type that’s rich in minerals and organic particles. Its water retention is good, yet it has adequate drainage. Silty soils are very easy to work with. The minerals and organic substances within make it one of the most fertile soil types.
• Pros: Contains minerals and nutrients, retains water well
• Cons: Fair drainage
Loamy soil is a combination of sand, silt, and clay soils with added organic compounds. It is one of the best soil types for growing cannabis as it offers optimal water retention and drainage, and it’s rich in nutrients and oxygen. Downside: This type of soil can be expensive.
• Mixture of sand, silt, and clay
• Pros: Excellent water retention and drainage, contains nutrients, high oxygen levels
• Cons: Expensive
Clay soils consist of fine mineral particles. This type of soil is heavy and not easy to work with. It is very rich in nutrients and minerals, which makes it a good option to include in organic grows. Clay soil retains water well, but has poor drainage.
• Fine particle size
• High pH
• Pros: Rich in nutrients, retains water
• Cons: Poor drainage, heavy and compact, hard to work with
AMENDMENTS TO IMPROVE SOIL QUALITY
If you’re working with natural soil, chances are it won’t be perfect for growing cannabis—not from the start, at least. The texture may not be optimal or it may have poor drainage, for example. But you can improve any type of soil by adding amendments, most of which can be found in your local grow shop.
Coco coir (coco fibre) is made from coconut husks. These light fibres provide excellent water retention and can lighten compact soils. Some use a pure coco substrate with special nutrients to cultivate their weed. But to amend existing soil, it’s a good idea to add anywhere up to 30% coco coir, depending on the composition of your base soil.
Perlite is the most widely used soil amendment. Perlite consists of very light, bright-white rocks that greatly improve the drainage and airiness of the soil. Perlite also has decent water retention. To amend your soil with it, add 10–15% of perlite. You can add more, but then your soil may become too light and nutrients may leach out. Good-quality commercial soils often come with added perlite.
Most cannabis growers are familiar with using clay pebbles as part of a hydroponic setup. But did you know they can also be used to enhance soil structure? Adding clay pebbles to the bottom of your raised beds and containers will assist with drainage and prevent water from pooling at the base—a large risk factor when it comes to root rot.
Growers can also add clay pebbles to the top of containers and beds to serve as a mulch. Here, they help to trap moisture in the growing medium by preventing excess evaporation. Clay pebble mulch also casts shade over the top layer of soil, suppressing weeds and keeping beneficial microbes sheltered from the hot rays of the sun.
Vermiculite, just like perlite, is a heat-treated mineral you can use to make your soil lighter.It is also excellent at retaining water. Although vermiculite shares some characteristics with perlite, the two have opposite uses: Use perlite to increase drainage and airiness, and use vermiculite to increase water retention. Luckily, you can use both, as perlite and vermiculite work well together. Around 10% vermiculite is beneficial.
Worm castings are normally seen more as a nutritional soil amendment as they contain a plethora of useful microorganisms that benefit growth. But worm castings will also improve the texture, drainage, and water retention of your soil. When amending your soil with worm castings, use about 25–30%.
If your DIY cannabis soil is rich in organic material, you will likely not need to add nutrients to it. As a matter of fact, some growers make the mistake of adding manure and vegetable scraps to their soil to “fertilise” it. This results in soil getting “too hot” for the plants, hurting their development in turn. If you want to put your vegetable scraps to good use in your garden, you first need to compost them.
If you think you need to amend your cannabis soil with nutrients, you can easily purchase bottled solutions tailored to a plant’s phase of growth.
PHOTOPERIOD VS AUTOFLOWERING
One factor to consider when choosing the right soil for your weed is whether you’re growing photoperiod or autoflowering plants. Autoflowers prefer a light mix with fewer added nutrients. A great substrate for your autoflowering ladies is a 50:50 mix of coco coir and a light, peat-based soil with some added perlite for drainage.
When growing autoflowers, stay away from heavily fertilised soils and certain amendments like bat guano, as these will be too hot and overload your plants with nutrients. The same is true for cannabis seedlings, which do not like high levels of nutrients.
Plant autoflowers in their final growing container in a cup-sized hole in the centre of the soil. Fill the hole with seedling/starter soil with no nutrients and place your seed in it. This way, your seedling can grow without being surrounded by the hot soil, which would otherwise burn it.
For photoperiod plants, start them out in small seedling pots/cups with soil that has little to no nutrients. Replant after a few weeks. More mature plants will tolerate higher nutrient levels much better than seedlings.
STORE-BOUGHT VS HOMEMADE
If you’ve just started growing cannabis, it may be best to simply get ready-made soil from the grow store. The reason for this is that good-quality cannabis soil normally contains everything your plants need for healthy growth, in the optimal ratios. If you want, you can further improve your store-bought soil with a handful of perlite for increased drainage, but otherwise you should be good.
BASIC CANNABIS SOIL RECIPE
On the other hand, there may come a time when you want to make your own soil. After all, why spend good money on soil if your homemade version is even better? Here is a recipe for a basic homemade cannabis soil.
• 1 part vermiculite
• 1 part coco coir peat
• 2 parts compost
• ½–1 cup worm castings (or humus)
1. Sieve the compost to remove larger chunks.
2. Soak the coco coir peat in warm water. Check the directions of the product to see what kind of volume you will be getting.
3. Use a bucket and mix the coco coir peat with the vermiculite.
4. Add the compost.
Done! Double-check the pH value of your homemade soil. It should be in the range of 5.8–6.3.
The above is a basic soil recipe that will serve you well for most grows, indoors and outdoors. But you can further enhance your soil mix by adding organic fertilisers.
Bat guano is an excellent and inexpensive organic fertiliser for flowering marijuana. You can add it to a soil mix or spread it on the topsoil and water in later. You can also look into time-release nutrients such as Easy Boost Organic Nutrition pellets. Add a cup of these to your soil to feed your plants for their whole life cycle—100g is enough for 2–3 cannabis plants. All that’s left to do is water!
No-till cultivation is a gardening method that allows the soil to remain undisturbed (no digging, stirring, overturning, etc.). This way, microorganisms in the soil can create a thriving ecosystem that replenishes the soil with good bacteria, helpful fungi, and other living organisms. No-till cultivation promotes organic matter retention and water absorption because nutrients are constantly being recycled throughout the soil.
To learn about no-till cultivation and its benefits, check out this article!
AMENDMENTS FOR ARID/DROUGHT CONDITIONS
If you’re growing outdoors in a hot climate such as Southern Spain or a similar location, you don’t want to “cook” the root zone of your plants. If you’re using pots, choose white plastic containers, as these help to keep the soil temperature at a reasonable level under the beating sun. You can also look to air pots or smart pots to keep the roots of your cannabis plants cool. As an additional measure to protect the soil from fluctuating temperatures, you can add layers of dry straw onto the topsoil.
If you’re growing in drought conditions where your plants may at times go weeks without rain, or if you can’t make daily trips to your guerrilla grow location, use water-absorbent polymers to keep them hydrated! You can get these from hydroponic grow stores or can cut them out of diapers.
For a guerrilla grow in dry conditions, dig a hole about 60cm deep and 30cm in diameter. Add a few cups of polymer crystals to the bottom of the soil mix and fill up with the remaining soil. Place your plant into the soil and water liberally. As your plant grows, the roots will soon reach the polymers so it can drink even during drought. Tip: Soak the polymers in a light nutrient solution for a double benefit!
Soil is the medium of choice for most cannabis cultivators. Here is what you need to know to get the most out of your soil grow!
The Definitive Guide To The Best Soils For Cannabis
Dirt, soil, growth medium—call it what you like, it’s an essential component for any cannabis growth operation. In fact, choosing the best soil for cannabis is one of the most important decisions you’ll make in the process of growing your own pot plants.
It’s so important that it can mean the difference between a successful harvest and complete failure. Which would you rather have: bountiful buds or a plant so unhealthy you can’t even compost it next year? That’s what using the right soil can do. So, yeah, a lot’s riding on your choice.
But what is the best soil for cannabis? What ’s the best pH? What if you’re growing outdoors? What if you’re growing indoors? The questions literally go on and on and on. But never fear, my friend. The experts at Honest Marijuana are here to help!
We’ve been growing some of the finest cannabis in the world for almost a decade. And we’ve been doing so the way mother nature intended: in 100-percent all-organic soil, without pesticides, chemicals, or growth regulators.
We’ve learned a lot in those years, and we want to pass on our knowledge to you. To do that, we’ve put together the definitive guide to the best soils for cannabis so you don’t have to worry about your head exploding while trying to sift through all the information. Let’s start our dirt-y adventure by discussing the basics of good cannabis soil.
The Basics Of Good Cannabis Soil
Cannabis is often considered a weed (hence the name) because the plant can pop up and thrive in diverse conditions. But that doesn’t mean you should just scatter your sensimilla seeds in the backyard and hope for the best. This isn’t Jack & The Beanstalk, bro.
Yes, your cannabis weed can grow in a wide range of soils, but to truly flourish—to produce lots of trichomes , THC, and other cannabinoids—it needs just the right balance of variables in the soil. These variables include:
- Proper drainage
- Good water retention (sounds counterintuitive to the first variable, but it’s not)
- Correct nitrogen to phosphorus ratio (this is done in the composting phase)
- The right balance of fungus to bacteria (a slight skew to the fungal side of the spectrum is okay because cannabis prefers slightly acidic soil)
- Soil pH of 6
Let’s discuss that last bullet point—pH—in a bit more detail.
Best Soil pH for Cannabis
pH (yes, the ‘p’ should be lowercase) stands for potential of hydrogen. It’s a chemical scale used to specify the acidity or basicity (alkalinity) of a substance ( usually a liquid).
For example, liquid drain cleaner and bleach (14 and 13.5 respectively ) are both very basic. Battery acid and hydrochloric acid (both 0 pH) are both very acidic. Between those two extremes lie more common items, like:
- Baking soda (9.5)
- Sea water (8)
- Pure water (7) (this is considered neutral on the scale)
- Coffee (5)
- Lemon juice (2)
Keep in mind that numbers above 7 are basic (alkali), while numbers below 7 are acidic.
So because soil contains water, it also has a pH. As mentioned in the section above, cannabis likes its soil slightly acidic. The ideal number is 6, but it can also flourish on either side at 5.8 and 6.3.
If your soil strays slightly higher than 6.3 or slightly lower than 5.8, the plant will still survive but it won’t produce as well . Keep your soil around 6 for the best crop.
To do this, you’ll need to purchase a soil pH tester. Sorry, there’s just no way around it. Sticking your finger in the dirt and then in your mouth is not an accurate test of pH.
The one consolation is that these testers aren’t very expensive. You can pick up a perfectly good soil pH tester for around ten bucks at Walmart or Amazon.
Of course, there are plenty of more expensive models that do everything but wash your dishes (some even do that), but there’s no reason to drop a c-note for this kind of functionality. Your basic, run-of-the-mill pH tester will do just fine.
Best Soil For Outdoor Cannabis
Natural soil (by that we mean soil found outside) comes in three main types:
But not all soil is just one type. They can be sandy/loamy, loamy/clay, sandy/clay, or any other combination of the three. To make things even more confusing, there can be different ratios of each soil type. And each soil type has its own benefits and drawbacks.
If you absolutely must grow your cannabis outside in the ground, we suggest digging a three-foot-wide, three-foot-deep hole and filling it with the organic super soil we show you how to make below. This will give your cannabis plant the proper drainage, water retention, and amount of nutrients to help it grow tall and strong.
You also have the option of growing your cannabis plants outside in a pot. Just fill a three- or five-gallon pot (or bucket) with the organic super soil we describe below and plant your seed. You will have to monitor the temperature, humidity, rainfall, amount of sun, and pests if you’re growing your cannabis plant outdoors.
The nice thing about growing your cannabis in a bucket or pot is that it’s portable. Weather not behaving? Take the plant inside. Pests attacking the leaves? Take the plant inside.
The only downside to doing this is that you’ll have to spend some money to control the light, air movement, and humidity. But once you’ve got the gear, you won’t be at the mercy of the elements (which can be unpredictable and cruel) and you can give your growing plant exactly what it needs to flourish.
Best Soil For Indoor Cannabis
The best soil for indoor cannabis growing is organic super soil and 420 fertilizer mix . We show you how to make these two indispensable items in the last two sections of this article.
The organic super soil, in particular, gives you the right balance of carbon, nitrogen, phosphorus, and a whole host of other nutrients to ensure that your cannabis plant gets exactly what it needs during every stage of growth . Add to that the 420 fertilizer (you can make yourself) and you’ve got a great recipe for growing tall plants with plenty of buds and lots of cannabinoids.
Of course, you can choose to purchase soil rather than make it yourself. This is particularly good for those who don’t have a lot of space outside to set up a compost pile. We’ll talk about the best bagged soils in the next three sections.
Best Potting Soil For Cannabis
If you must buy a bagged soil and your local garden store doesn’t have a lot of choices, anything with the words “organic potting soil” or “organic potting mix” will work. It’s not the ideal, but it will do in a pinch.
Your best bet is one of the organic soils listed in the next section or the homemade super soil we talk about at the end of this article.
One thing you want to look for when buying potting soil for cannabis is that it does NOT contain any slow-release chemical nutrients. If your potting soil contains these time-released chemicals, it could give your marijuana plant the wrong nutrients at the wrong time. That could spell disaster for your cannabis crop.
If your garden store has more of a variety, look for one of the following brands.
Best Organic Soil For Cannabis
These organic soils have been tried and tested as cannabis-friendly products. You’re still better off producing your own organic super soil and 420 fertilizer, but these can work in their absence. Visit any marijuana-grow chatroom and you’re likely to see these products mentioned more than once.
Black Gold Soil For Cannabis
For years, Black Gold was the go-to potting soil for the discerning cannasseur. Black Gold also makes other additives such as peat moss, earthworm castings, perlite, compost, and vermiculite you can use to supplement the lack of necessary cannabis nutrients.
Fox Farm Soil For Cannabis
Fox Farm is another bagged soil used by cannabis growers. The Ocean Forest mix is particularly effective at giving your cannabis plants just the right soil conditions to grow their best.
To give you an idea of what’s in the mix, here’s a breakdown of the Ocean Forest ingredients:
- Sea-going fish emulsion
- Crab meal
- Shrimp meal
- Composted forest humus
- Sphagnum peat moss
- Worm castings
- Oyster shell
- Sandy loam
- Bat guano
- Granite dust
- Norwegian kelp
Doesn’t sound appetizing to me, but cannabis plants just love it.
Best Soil For Autoflowering Cannabis
The amount of light a plant gets during the day is responsible for making that plant flower . These are called photoperiod plants. Cannabis plants grown outdoors need between 12 and 15 hours of light per day. That usually doesn’t happen until later in the summer.
Of course, that variable can be controlled by growing your cannabis indoors (where the plant needs closer to 18 hours of fluorescent light).
But some cannabis plants are what’s known as autoflowering. That means the plant isn’t dependant on the amount of light it receives to trigger its flowering stage. Instead, autoflowering cannabis plants will transition to the flowering stage when the plant reaches a certain phase of development.
Autoflowering cannabis prefers a more light, airy soil with a relatively low level of nutrients. That makes many of the soils and mixes discussed above less than ideal. That doesn’t mean you can’t use “normal” soil. It just means that you’ll get a better result with a lighter soil.
Try mixing your own autoflowering soil with the following recipe:
- 3 parts compost
- 3 parts peat moss
- 2 parts wet perlite
- 1 part wet vermiculite
For those of you using regular, photoperiod marijuana seeds, the next two sections will be your definitive guide to making the best soil for cannabis.
How To Make Your Own Organic Super Soil
To make your own organic super soil, you need to be able to control things like temperature, airflow, and carbon-to-nitrogen ratio. Check out Honest Marijuana’s How To Grow Marijuana: The Ultimate Organic Guide for advice on these variables. Once you’ve got all that straight, here’s a step-by-step guide to making your own soil.
- Mark out a three-by-three square on the ground.
- Lay down a four-inch layer of carbon material like dry leaves or straw so that it covers that three-by-three square.
- Add a four-inch layer of nitrogen material like livestock manure or coffee grounds.
- Top that with a half-inch layer of blood or bone meal.
- Repeat the first three steps—layer by layer—until your pile is three feet high.
- Leave the pile to decompose.
- Turn the pile at least once a week, but not more than every three days.
- The composting process is complete when the soil is soft, crumbly, dark black, and smells sweet.
You can use that soil for planting your cannabis seeds and for mixing your own 420 fertilizer.
How To Use That Soil To Make 420 Fertilizer
This 420 fertilizer can be used throughout the grow process to keep your cannabis plant happy and healthy. Here’s the recipe.
- Lay down a large tarp or purchase a plastic kiddy pool. We like the kiddy pool because it makes mixing and corralling the fertilizer easier.
- Spread a one-inch layer of your organic super soil.
- Mix in a scoop each of coco fiber and mycorrhizae .
- Toss in:
a. 0.75 kilograms of rock phosphate
b. ⅛ cup of Epsom salts
c. ¼ cup of Azomite (trace elements)
d. ½ cup of sweet lime (dolomite)
e. 1 tablespoon of powdered humic acid
- Add another one-inch layer of super soil
- Spread on 1 kilogram of bat guano.
- Add another one-inch layer of super soil.
- Spread on 1 kilogram of blood meal.
- Add another one-inch layer of super soil.
- Spread on 1 kilogram of steamed bone meal.
- Add another one-inch layer of super soil.
- Mix everything together with a shovel.
- Fill a garbage can (or garbage cans) about ¾ full with this new mixture.
- Pour 2.5 gallons of water in each can.
- Leave this to steep in the sun for one month.
After thirty days, you can use this liquid to fertilize your growing pot plants.
Some Tips We’ve Learned Along The Way
Here are a few other essential tips we’ve learned along the way to make creating the best soil for cannabis just a bit easier.
- Collect all the ingredients before you begin.
- Take it slow. There’s no need to rush.
- Start recording everything you do (in regard to the soil) so you can figure out how to improve the process.
- Learn how to use and read a pH tester.
- Get friendly (not too friendly!) with the folks at your local garden center or greenhouse. They can provide a wealth of information about all things soil.
After that, just dive in and get your hands dirty. That’s the only way you’re going to learn. Happy growing!
Thinking about growing your own cannabis? Not sure what soil to use? The experts at Honest Marijuana tell you everything you need to know to grow the best plants.