For novice growers it can be very daunting to choose the best nutrients for your cannabis, and often you spend a lot more money than is necessary. With so many options to choose from, ranging from hydroponic growing to organic nutrients , new growers can feel overwhelmed. But with a little knowledge about the needs of cannabis plants and how they absorb and use nutrients, you can confidently choose the products you need without breaking the bank.
What Elements Does a Cannabis Plant Need?
Your cannabis plant needs one main group of elements, collectively known as macronutrients . Below you will find a list of the mineral and non-mineral elements that your plant needs to feed on.
Mineral nutrients obtained from the soil:
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
Non-mineral elements deriving from air and water:
The three numbers on fertilizer bags, nutrient solution bottles, or other additives indicate how much of the three main elements (nitrogen, phosphorus, and potassium) is present in the product. For example, a product labeled “ 10-4-4 ” will contain 10% nitrogen, 4% phosphorus, and 4% potassium by weight. They are always listed in this order, NPK .
All other mineral nutrients are grouped into the micronutrient category, as they are used in much smaller quantities. This group consists of the following elements:
Although cannabis plants require minimal concentrations of these elements to thrive, they are still vital to the overall health and growth of the plant.
Below we will look at the main types of nutrients used by cannabis growers today, as well as their appropriate use. Before you start growing, however, you'll want to learn about the basic mechanisms by which plants absorb water and nutrients, osmosis, and active transport.
Hydroponic (Soil-Free) Nutrients for Cannabis
Hydroponic growing is, simply, the practice of growing plants without soil, usually through some other substance, such as rock wool, clay pebbles, coconut fiber, or some type of mix. Many of the premium “fertilizers” sold for growing cannabis are actually soilless mixes. Most indoor cannabis growers use the hydroponic method, while still using buckets of “compost” and watering each plant.
For this reason, the majority of nutrients sold specifically for growing cannabis are hydroponic nutrients. These products include concentrated mineral salts, usually in liquid form but sometimes also in powder form, which must be diluted in water to the level suitable for the plant.
Nutrients must be water-soluble for the plant to absorb them. Liquid products are sold in two parts (usually labeled “part A” and “part B”), because they contain elements that will precipitate out of solution if mixed together at high concentration, thus becoming unusable. But this is not a problem if they are combined in the right amount of water.
The products are also divided into "Growth" solutions, with high concentrations of nitrogen, necessary for plant growth, and "Flower", with high concentrations of phosphorus for flower development, because the cannabis plant needs different nutrients during the different stages of growth.
Great care must be taken when administering hydroponic nutrients, as giving too many can lead to damage to the plant, or even its death. A general rule of thumb is to start at about 25% of the level recommended on the product label, and gradually work your way up to 100%. Hydroponic nutrients are often used by soil farmers with good results, but this technique is not recommended for beginners.
Soil and Organic Nutrients for Cannabis
What distinguishes soil from hydroponic is the presence of non-inert organic matter, such as humus , compost , manure , and vermicompost , which contains many macro and micronutrients. However, much of the nutritional value of these substances is contained in a non-soluble form, and must be processed by soil microbes and fungi in order to be useful to the plant. Nonorganic nutrients created for growth on soil are less common in nurseries because they can quickly take root in the soil, damaging soil life, and can prevent roots from absorbing water and nutrients.
Organic fertilizers and nutrients for cannabis are not forgiving; they usually contain nutrients that are not directly soluble and other elements beneficial to soil organisms. The novice grower who decides to use soil as his growing medium should be careful to stay on organic fertilizers and nutrients.
The least expensive way to do this is to use things like blood meal and fish meal for nitrogen, bone meal and bat guano for phosphorus, wood ash and algae meal for potassium, lime dolomite for calcium and magnesium, and magnesium sulfate as a source of magnesium and sulfur. Most of these items can be purchased cheaply at your local nursery and then mixed in small quantities into the soil before planting. If you do it correctly, then you will only need to water your plants and add occasional carbohydrates to nourish the life in the soil. There are also soil mixes available on the market that already contain the right mix of this type of ingredients.
Alternatively, there are pre-mixed organic nutrient solutions you can buy, which take the guessing game out of feeding your plants. They tend to be expensive, but the payoff is that you can simply follow the manufacturer's dosing schedule and get good results.
The key to successfully growing organically is cultivating a diverse and generous population of soil microbes and mycorrhizae . Many premium potting mixes already contain these organisms, and there are many (often expensive) additive products available, which add life to your growing medium. However, the best (and cheapest) method to inoculate your soil is through AACT , “ actively aerated compost tea ,” a watery compost you can make yourself with a few inexpensive products. By using this technique, you may find that you don't need to add many nutrients or fertilizers; the life of the soil will process the organic matter present in the soil, transforming it into nourishment, which the plant can immediately absorb.
There are many ways to grow cannabis, and each has benefits and disadvantages. Organic potting soil is more forgiving of mistakes and less-than-ideal conditions, but often produces smaller yields and slower growth. Hydroponic and synthetic nutrients can offer large yields and faster flowering times, but they need a lot of attention and knowledge to be successful. The best advice for the novice grower when selecting nutrients and fertilizers is to make sure you use products that are compatible with your technique and medium, and that they are compatible with each other. Doing a little research before your first grow can avoid wasting money on unnecessary products. Happy growing!