Whether you want to call it dirt or a growth medium, soil is a crucial component for growing marijuana. Choosing the best soil for your weed is arguably the #1 most important decision you’ll make when growing cannabis at home. Getting it right is likely to be the difference between a bountiful harvest and utter failure.
Newcomers are often fooled by the apparent simplicity of picking soil, and frequently make mistakes that cost them their harvest. The truth is, there are a lot of considerations to be made.
For example, the soil you use for indoor growing is not the same one you’ll need for an outdoor grow. Then there is the small matter of things like pH, drainage, and a host of other criteria.
There are a large number of soil brands available, which is both good and bad news. You get a lot of options but with so many choices, how do you determine the best soil for growing your marijuana? The key is to analyze your situation, and our guide will help do the rest.
Pros & Cons of Growing Cannabis in Soil
Ultimately, you can choose between soil or a hydroponic system if you wish to grow weed at home. A hydroponic system can be extremely effective, but it is also expensive. Generally speaking, those growing their cannabis for the first time should choose soil.
The roots of your plants will extend deep into the soil as it looks for nutrients and water. That’s why indoor systems, which have a lack of space, need to create smaller root systems for marijuana. Regardless of the root system you choose, make sure the temperature in the growing area stays around 68 degrees Fahrenheit. And of course, ample water and oxygen in the soil is a must.
Irrigation in soil is easier than with hydroponic systems, as is fertilization. With so much information gathered from thousands of years of growing, you can quickly become a soil expert as long as you read the right articles!
On the downside, soil requires a ton of space, and it is very heavy. You’re also more likely to have issues with pests than with a hydroponic system.
Choosing the Right Cannabis Soil Container Size
The size of the containers you choose will dictate the size of the marijuana plant’s root system. The more space the roots have, the faster they grow. You can expect problems to arise when the roots outgrow your container, so choose wisely! There is no need to go beyond a 10x10x10 cm container while your plants are still seedlings.
Once it reaches a height of 25cm, transplant the plant(s) to a container that is at least double the size of the first one. Once your plant hits the lofty heights of 80cm, move it to at least a 12-liter container. Once your plant hits a meter in height, you’ll need an even bigger container. This process continues all the way until harvest.
Watering Your Soil
The soil type and growing environment determine the way you water the soil. Obviously,hot climates need more water, and cooler climates need less.
When you water the plant, it moves important nutrients and minerals to the roots, and then they are sent to the rest of the plant. Water cools overheated plants down and is a critical ingredient for photosynthesis. The best advice we can give is to water the soil until it is moist, but NOT wet to the touch. Overwatering aids the growth of harmful fungi which can result in root disease, so be careful!
Quality Soil for Cannabis
Natural soil comes in four varieties: sandy, silt, loam, and clay, so you’ll be in for a nasty surprise if you think that soil is just one ‘type.’
Many soils will have a combination of at least two of the four types, so you can have sandy/silty, loamy/clay, silty/clay, and so on. If that isn’t confusing enough, there can also be different ratios of every soil type. It is an important consideration, however, because each soil type has its pros and cons.
Sandy soil is known for its large granular size and has a low pH. The issue with this type of soil is that it gets dry easily and often experiences difficulties in moisture absorption. The nutrients also get washed away, and nitrogen in particular is quickly lost from sandy soil.
On the plus side, sandy soil is easy to prepare for cultivation, offers good drainage, and contains high oxygen levels. It is one of the best soils for growing weed indoors.
This soil type is composed of minerals such as quartz and fine organic particles. Although they hold moisture, silt soils have decent drainage and are one of the easiest to work with when wet. Also, silt soils are among the most fertile, which gives you a chance of a decent-sized harvest. And with frequent irrigation, you can extend the length of the growing season. Silt soil is one of the best soil types for seedlings.
Loam soil is actually a combination of sand, silt, and clay; typically in a 40/40/20 ratio. It has at least 20% organic compounds and can vary from being easy to work with to extremely complex. To identify a loam soil, squeeze it; it should form a loose ball that quickly threatens to break apart.
This is a common marijuana potting soil, and has an almost neutral pH. It offers good drainage and water retention, contains high oxygen levels, and is naturally fertile. However, it is by far the most expensive option.
This type of soil is sometimes regarded as the best organic soil for cannabis. Clays are made up of fine crystalline particles that have been created via chemical reactions amongst minerals or other natural resources. Clay soil can be molded or shaped, but it is hard to work with and drains badly.
If you try to use this kind of soil, expect to have difficulty in getting the plant’s roots to penetrate the surface. Clay soil has a high pH, and while it stabilizes plants, the soil is heavy, and it requires a lot of effort overall.
What Does Loam Soil Look Like?
Loam is, without doubt, the favorite weed soil of growers. It makes the best soil for potted plants and is probably the best soil for plants in general. It contains a good balance of all three soil types (Clay, Silt, and Sand) along with hummus, of all things.
This combination ensures that loam has high calcium levels, but it also has a relatively high pH.
Loam also has a dark color and is soft, dry and crumbly when you hold it. Although it offers a tight hold on plant food and water, it drains extremely well, and the air can freely move between the particles down to the marijuana plant’s roots.
How to Make Loam Soil
Even though Loam soil is a combination of the three main soil types, don’t think you can create loam soil by adding clay soil to silt, or vice versa. If you try to add sand to clay, for instance, you’ll end up with a cement-like texture. In reality, creating loam soil for your plant is not a straightforward or quick process.
It is however the best soil for cannabis, which means it is worth the time and effort that you have to put in. No matter what type of soil you have, creating loam involves adding organic matter to it each year. The decomposing plant material creates the excellent drainage conditions your weed needs.
The trouble with organic matter is that it gets depleted rapidly, meaning you have to amend it on a season by season basis. The amount of work you must do depends on the balance of your existing soil. For instance, if it has high amounts of clay or sand, you’ll have to add large amounts of organic matter several times a year. In general, adding a two-inch layer of organic matter onto the surface of the garden and working it into the first couple of inches of soil should be enough.
Buy Only the Right Soil for Your Cannabis Plants
It is normal to go to your local garden store full of enthusiasm, only to be knocked back by the enormous number of options. First of all, please note that buying it in bulk could be a mistake because there are no certifications or standards attached to soil quality. Believe it or not, some of these sellers provide you with soil from construction sites or even soil excavated from basements!
When buying soil for weed, make sure you understand the basics of good cannabis soil. If you want your plants to offer lots of cannabinoids and trichomes, you have to pay attention to several variables including:
- Drainage, Texture, and Water Retention
Drainage, Texture & Water Retention
When it comes to finding the right pot soil for growing cannabis, its texture, drainage ability, and water holding ability are arguably the most important aspects. Your plant has no hope of producing a good yield if it doesn’t have the right mixture of water and oxygen in the roots 24/7. If there is too much water, the roots won’t get enough oxygen. If there isn’t enough water, the roots can dry out quickly and become damaged.
High-quality marijuana soil should have:
- A rich and dark color.
- Loose texture.
- Excellent drainage. In other words, it should NOT make a pool on top of the soil for more than a few seconds.
- The ability to retain water without becoming muddy.
It is unlikely that your cannabis soil will have the ideal drainage, texture, and water retaining abilities. Fortunately, there are a host of amendments available to alter the drainage, texture, and water retaining ability of your soil. Here are four of the most popular.
- Coco Coir: This is made from coconut husks, and manages to improve water retention without causing the soil to become heavy. When you use Coco Coir, the roots of your plant should develop quicker, and you’re less likely to overwater. You can actually grow your marijuana in pure coco coir, but a maximum of 30% is best for a productive soil amendment.
- Vermiculite: This enhances water retention, and causes your soil to become ‘lighter.’ It works especially well with Perlite.
- Perlite: This is probably the most commonly purchased amendment, and is ideal for practically any soil mix. It consists of airy ‘rocks’ known for their white hue, and it looks a bit like popcorn and improves drainage while adding oxygen. Use 10-20% to improve water retention. You can go as high as 40%, but you risk leaching nutrients faster. If you use Perlite and Vermiculite, don’t go above 50% for the two combined.
- Worm Castings: Yes, we are talking about worm poo! Once you get past the initial horror, you’ll find that worm castings are adored by your marijuana plants. They improve water retention, drainage, and texture, and their natural nutrients are quickly broken down and typically include useful microorganisms since they goes through the digestive systems of worms. Keep the level of worm castings down to around 30%.
As long as you choose correctly, your cannabis soil should already have a large array of nutrients because it is comprised of organic material. One basic mistake made by cannabis growers is to try to add organic material such as animal manure and rotting vegetables directly to the plants as fertilizers. You must break down the material first if you want your marijuana plants’ roots to absorb the nutrients.
It is especially important for indoor growers to find soil with a lot of nutrients because they don’t benefit from nature in the same way as outdoor growers. Use heat to sterilize the soil and add nutrient-rich potting soil mix. You can make it yourself, but newbies should purchase it from the garden store. Water the soil correctly, keep it in a room with a temperature of 68 degrees Fahrenheit and test the pH every so often.
In case you weren’t aware, pH means ‘potential of hydrogen.’ It is a chemical scale which is used to determine a substance’s alkalinity or acidity. The scale goes from 0-14. A pH of 7.0 is neutral (pure water is 7.0, for example). Everything from 0-6.9 is acidic, while everything from 7.1 to 14 is alkaline.
Battery acid and hydrochloric acid have a pH of 0, while liquid drain clearing fluid has a pH of 14. Ideally, your cannabis soil will be slightly acidic. Most experts believe that the ideal pH is 6.0, but you are on solid ground if your soil’s pH is between 5.8 and 6.3. Your crop will survive outside of this range, but the yields will be much smaller. Obviously, if you stray too far from the 5.8-6.3 range, the plants will die.
Soils for Cannabis: Recommended by MarijuanaBreak.com
If you are a beginner grower, it is imperative that you purchase your soil from a garden store. In fact, did you know that the vast majority of expert growers also buy their soil? A handy tip (if you don’t want to mention weed) when talking with a store employee is to ask about the right kind of soil for tomatoes.
At MarijuanaBreak.com, we have taken the liberty of recommending a few store-bought soils for your cannabis plants (though please note that these are NOT for seedlings, as they contain too many nutrients). These are soils designed to help your plant thrive once it reaches the vegetative stage. Otherwise, you need to look at potting soil brands when your plant is still a seedling.
Before we continue with the best soil brands for growing cannabis, let’s look at general guidelines for indoor and outdoor soil.
Best Soil for Indoor Plants
Overall, you can’t go wrong with an organic super soil and fertilizer mix. The super soil offers the ideal mix of nitrogen, phosphorus, carbon, and a myriad of other nutrients. You can make them yourself, but once again, we recommend investing in store-bought pot soil.
Best Soil for Growing Weed Outdoors
When growing weed outdoors, make sure you use soil that feels fluffy in your hands. It needs to possess a reasonable amount of nutrients, and good drainage is essential. Compost and store-bought fertilizer can form a fertile and rich base. Crucial nutrients include Nitrogen, Potassium, and Phosphorus.
Best Cannabis Soil Brands
Best Simple Soil – Roots Organics 707
This organic blend comes from Aurora Innovations, and its peat moss base aids water retention. There is a relative lack of amendments, however, which means you can liquid feed your plants or topsoil them at your leisure. For best results, wait up to 14 days before using 707 on your plants.
Best All-in-One Soil – Red’s Premium Biochar-Based Soil
This ready to plant soil is created by Miller Soils in Colorado. It contains a variety of amendments while the biochar offers a great living arrangement for microbes. Red’s Premium helps with nutrient and water retention, and it is designed for immediate use since it has a wide variety of useful nutrients attached. The main benefit of this soil is that you don’t have to be concerned about feeding it more than a handful of times.
Best of the Rest – Fox Farm Ocean Forest Soil
The Fox Farm company has been in existence for over three decades, and is a well-renowned maker of cannabis soil in the United States. Its Ocean Forest soil mix contains a high degree of nutrients with ingredients such as fish meal, crab meal, and bat guano. You can use it on seedlings, but it’s probably best used on larger plants because of the level of nutrients it contains. If you want to use it on seedlings, consider adding Fox Farm Happy Frog on top to reduce the risk of nutrient burn in the first week or two.