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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:

  • Sandy
  • Loamy
  • Clay

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.

  1. Mark out a three-by-three square on the ground.
  2. Lay down a four-inch layer of carbon material like dry leaves or straw so that it covers that three-by-three square.
  3. Add a four-inch layer of nitrogen material like livestock manure or coffee grounds.
  4. Top that with a half-inch layer of blood or bone meal.
  5. Repeat the first three steps—layer by layer—until your pile is three feet high.
  6. Leave the pile to decompose.
  7. Turn the pile at least once a week, but not more than every three days.
  8. 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.

  1. 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.
  2. Spread a one-inch layer of your organic super soil.
  3. Mix in a scoop each of coco fiber and mycorrhizae .
  4. 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
  5. Add another one-inch layer of super soil
  6. Spread on 1 kilogram of bat guano.
  7. Add another one-inch layer of super soil.
  8. Spread on 1 kilogram of blood meal.
  9. Add another one-inch layer of super soil.
  10. Spread on 1 kilogram of steamed bone meal.
  11. Add another one-inch layer of super soil.
  12. Mix everything together with a shovel.
  13. Fill a garbage can (or garbage cans) about ¾ full with this new mixture.
  14. Pour 2.5 gallons of water in each can.
  15. 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.

  1. Collect all the ingredients before you begin.
  2. Take it slow. There’s no need to rush.
  3. Start recording everything you do (in regard to the soil) so you can figure out how to improve the process.
  4. Learn how to use and read a pH tester.
  5. 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.