The Best Soil and Nutrients for Growing Weed

Before a cannabis seed can sprout and grow, it needs a medium in which to develop, and soil is, undoubtedly, the most used for this purpose. Along with water, light, and nutrients, soil or substrate is an essential part of any crop. It can make the difference between vibrant and healthy plants or an empty and disappointing crop. In this article we look at the best soil for cannabis plants and how it interacts with the nutrients that each strain may need.

When growing cannabis, there are “soil-less” options, such as hydroponics, aeroponics, or coconut fiber, all of which have distinct advantages and disadvantages. But, for many marijuana growers, there’s nothing better than soil to grow the plant in. After all, it is the original growing substrate. And, while soil is an excellent medium that offers many advantages, not all soils are created equal.

Cannabis is a family of hardy plants that has thrived in different climates and conditions; from warm, tropical places with fertile soils, to relatively cold and harsher climates with less hospitable soils. But, while cannabis can grow successfully under different circumstances, selecting various soil qualities to make that will favor your plants can drastically benefit their yields and the final quality of your buds.

What soil characteristics are most important for growing marijuana?

High-quality soil provides an optimal environment for root growth, nutrient absorption, and overall plant health. In the end there are four main factors you need to pay attention to when it comes to choosing the best substrate. These include:

• Water retention
• Drainage
• Texture
• pH

Retention and drainage are likely to have the greatest impact on the performance of your plants, as they will require a constant supply of water and oxygen. Ultimately, however, water and oxygen compete for space within the soil. For example, if there is too much oxygen (as in sandy soils), there will not be much water, and vice versa. On the other hand, if the soil contains too much water (as can happen with clay soils, featuring high retention and low drainage), plants can develop root rot.

You should also consider the texture of the soil you choose, which will ultimately determine how well plant roots can spread and grow. For example, something like sand is very loose, allowing roots to grow and spread easily. However, if it is too loose, the texture may not support the plant very well, especially as it grows. Plant roots may have difficulty penetrating and spreading through hard, heavy textures, such as clay.

Finally, consider the pH of the medium. Like many plants, marijuana grows best in slightly acidic soils with a pH below 7.0. The optimal range to aim for is 5.8 – 6.2. Fortunately, this is fairly easy to maintain if you regularly use a pH meter and adjust your fertilizer solutions as needed.

What is the best soil for cannabis?

Considering all these factors, an entire industry has emerged to provide growers with an ample supply of marijuana-specific soil. These soils are usually rich in nutrients. In addition, they contain a mixture of types of materials in proportions ideal for healthy cannabis growth.

Given the complexity of soil science, we’re not going to blame you for wanting to buy a prefabricated blend and to start growing marijuana without worrying about the quality of the substrate. In fact, this is recommended for most novice growers, because replicating these commercial soil mixtures with the same macronutrients, micronutrients, and ideal qualities can make the cannabis growing process much more complicated.

But, if you want to make your own soil, there are multiple combinations that have been tested, with excellent results. One of the most used is this recipe: 40% high-quality black soil and/or compost as the base of the substrate (it has the highest nutrient content of the mixture, and can be used together or separately); 25% peat (its function is to retain water and nutrients, aerate the substrate, and reduce its compaction); 10% vermiculite and 10% perlite (which have a great capacity for water retention, as well as oxygenation); and, finally, 15% humus, which has a remarkable nutrient content, helps regulate the pH, and maintains the micro-life of the soil.

What type of nutrients are best suited for growing marijuana?

Nutrients are essential for the growth, development and overall health of cannabis plants. These minerals help foliage to develop, roots to stretch, and buds to become large and sticky. The essential nutrients for growing cannabis are nitrogen, phosphorus and potassium (NPK). These three are macronutrients, which means that plants need them in large quantities. We also have secondary minerals and trace elements (micronutrients).

The secondary minerals are calcium, magnesium and sulfur, which are necessary for healthy plants, but in much smaller quantities than NPK. Micronutrients are not the main “food” of marijuana, but they support several vital processes, with these including manganese, boron, iron, zinc, copper and even molybdenum.

When growing in soil, there are two main ways to obtain these nutrients for plants: buy or create a nutrient-rich soil in which these elements are available for the plant, as needed; or start with a relatively neutral soil and provide the nutrients yourself, usually by adding them each time you water the plants.

What is the optimal nutrient ratio for healthy plants?

You can make marijuana nutrients from organic matter at home (for example, by composting) or buy them from a garden store. Plants need varying amounts of NPK at different stages of their development, and brands vary in terms of what they consider optimal, but these are, generally, the amounts:

• Vegetative growth phase: NPK: 2: 1:1 ratio or similar (e.g., 10-5-5). At this stage, the plant needs more nitrogen to favor growth and branching.
• Early flowering phase: NPK: 1:2:2 ratio or similar (e.g. 5-10-10). As the plant begins to bloom, more phosphorus is needed to foster the development of flowers and buds.
• Late flowering or ripening phase: NPK: 0:3:3 ratio or similar (e.g., 0-15-15). At this stage, the plant requires more potassium to facilitate flower development and promote bud ripening.

Some manufacturers use all-natural sources, while others use chemicals, perfect for hydroponic and aeroponic installations. In addition, when you use natural sources, you can introduce microorganisms that turn into food for plants. Use compost, bat guano, earthworm humus or other natural sources.

Commercial brands may also offer supplements, in addition to the usual fertilizer, which contain low amounts of NPK and focus on micronutrients to help address deficiencies and boost growth, flowering and maturation.

Although plants depend on these nutrients throughout their life cycles, problems can sometimes occur when an excess of them is produced.

As salts accumulate around the roots, over time cannabis plants may struggle to absorb their food and maintain a well-balanced diet. This is why, when “feeding” your marijuana plants, follow the maxim of “less is more”: it is always easier to solve a nutrient deficit than to redress overfeeding.