Plants, just like humans, need a well-rounded variety of foods to live happy and healthy lives.
Cannabis plants are no exception, needing a wide range of nutrients to develop fragrant buds which burn cleanly. There are several types of nutrients that cannabis plants need to thrive.
When plants lack these nutrients, they begin to show signs of stress. This indicates your plant is suffering from a nutrient deficiency. To avoid that and feed your plant everything it requires, read our guide below.
There are two basic kinds of nutrients in plants.
Mineral nutrients are naturally found in soil and can usually last a few weeks before they need to be replenished by the grower (though supplementing these nutrients can help the plant grow faster).
These nutrients can be supplemented after a soil test using store-bought fertilizers and nutrient solutions.
Then, there are hydroponic nutrients, the same chemical compounds found in soil but supplied entirely by the grower since hydroponic grows do not use soil to hold or supply the necessary nutrients.
Hydroponic nutrients come in the form of nutrient solutions, which the grower mixes with water and applies to the plant roots through a variety of hydroponic grow systems.
It is possible to grow with just the nutrients that naturally occur in the soil and water. In fact, most growers apply way too much fertilizer to their gardens.
Experienced growers tend to recommend starting slow with products, using about a quarter of the recommended dose and increasing as needed.
TIP FROM MASTER GROWER JORGE CERVANTES: Most nutrients that are applied are washed away. Nutrient uptake by plants requires complex chemistry in the root zone (rhizosphere).
Nutrients are often applied to the substrate and not taken up by roots. The nutrients do not enter the plant’s system and wash away. Overall, drip irrigation systems are usually more recommended because they are delivered directly to the root zone with little evaporation or waste.
The basic nutrients a cannabis plant requires are NPK:
The three numbers found on the front of the nutrient and fertilizer packaging indicate the NPK content. While NPK is the three core nutrients required by cannabis plants, there is a wide range of other nutrients that help grow healthy buds.
Among these nutrients are the non-mineral elements Carbon, Hydrogen, and Oxygen which can be found in air and water.
The nutrients found in soil, fertilizer, and nutrient solutions are known as mineral elements and are divided into two sets of categories. The first set of categories includes Macro, Secondary, and Micronutrients, which we’ll touch on below.
The second set of categories includes mobile and immobile nutrients. If a nutrient is mobile, there is a bit of a buffer time before the plant shows signs of nutrient deficiency. That’s because a mobile nutrient can move throughout the plant. For example, Nitrogen—a mobile nutrient—can move from older leaves to younger ones to make up for a deficiency and allow newer leaves to thrive.
One thing to remember about nutrients is that a plant absorbs them through the roots. They must be mixed in with water so the roots can absorb them.
It’s essential to follow the instructions on nutrient packaging very closely since an improper mix of nutrients can block the roots from being able to absorb them even if they are present.
So it’s possible that if a plant is exhibiting signs of nutrient deficiency even though you’ve added that nutrient to the soil, it’s because you are mixing the nutrients improperly and adding too much.
It’s also important to remember that the cannabis plant needs different concentrations of nutrients depending on its growth stage. For example, during its vegetative stage, the cannabis plant loves plenty of Nitrogen, but at the later flowering stage, Phosphorus becomes far more critical.
All plants need Nitrogen to grow, but cannabis especially likes Nitrogen during its vegetative phase. It’s important to remember to replace nitrogen often, as cannabis absorbs it rather quickly. However, an excess of nitrogen could cause the flower to burn poorly, according to Jorge Cervantes’ Grower’s Bible.
This element is used by cannabis across several stages of its lifecycle but is vital during germination and flowering. Cannabis plants use Phosphorus to transfer energy from one part of the plant to the other. It’s an essential element in developing healthy roots.
This element is used in all stages of growth and is important for upholding the plant’s immune system against harmful mold and bacteria. According to the Grower’s Bible, phosphorus is vital for the plant’s light intake, and the proper amount can improve the flavor of the buds.
This element is used to help the plant absorb light and develop flowers. It’s important to remember that cannabis plants often have a deficiency in magnesium which can be corrected with dolomite lime.
This element is important to maintain because it helps the cannabis plant absorb other nutrients. Deficiencies often occur outdoors and in soils with extremely high humidity and can inhibit the development of buds.
Sulfur is important for the development of the oils and flavor of the plant. It also allows the plant to breathe while balancing pH, according to the Grower’s Bible.
Also called trace elements, micronutrients help the cannabis plant use other nutrients. It’s important to look for these elements in chelated form, which means they are water-soluble and mixed with other minerals so that the plant’s root system can easily absorb them.
These are the micronutrients to shop for:
There are also several other trace elements like Silicon, Nickel, and Molybdenum which cannabis is rarely deficient in and are added to many retail fertilizers.
There are many different brands of cannabis nutrients on the market, and they can differ considerably.
For a better understanding, they can be divided into four major categories:
There are two basic types of chemical fertilizers that are available for cannabis growing: granular and water-soluble.
As the name suggests, soluble fertilizers are nutrients mixed into water and are recommended as the ideal alternative to granular fertilizers, which are sand or grain-like substances that are far more difficult to flush out if too much fertilizer has been applied.
Chemical fertilizers are preferred for beginner growers since they come premixed with the necessary nutrients. When using chemical fertilizers, it is important to follow the instructions and avoid brands that do not offer detailed descriptions of their content.
Most fertilizer brands provide their customers with feeding charts. This chart will be your guide to providing your crop with what it needs when it needs it.
A feeding chart usually states a 12-13 week growing cycle, although this can vary depending on the brand.
What you should know about this chart is that it will tell you what nutrients to give the plants and in what proportion during the different weeks of their life cycle.
Nutrients are usually applied once a week, and most fertilizer brands will give you a ratio of feed to water (in liters or gallons). Although some may have slightly more complex instructions, the basic principle is the same.
Overfeeding or underfeeding can stress and damage your cannabis plants. Some of the problems you may encounter in your crop are:
pH Imbalance: pH problems can be caused by imbalances in the medium, water, and nutrients. If left untreated, pH problems impede plant growth and reduce crop size and quality.
Nutrient Burn: Nutrient burn is usually caused by overfeeding or nutrient buildup in the growing medium.
Nutrient Lockout: Nutrient lockout is caused by nutrient buildup around a plant’s roots, or pH imbalances, and prevents them from absorbing available nutrients. It’s usually treated with a flush, pH checks, and nutrient adjustments.
Overfeeding: Overfeeding with chemical fertilizers and boosters can burn your plants. Overfeeding should be treated quickly with a root flush, pH stabilization, and a new feeding program.
Nutrient Deficiency: Nutrient deficiency can be caused by underfeeding or nutrient starvation. Nutrient deficiencies are treated by increasing/introducing more nutrients or by first addressing the nutrient blockage.
Cannabis plants are sensitive to nutrients, and there’s a fine line between properly feeding your plants and burning them with chemicals.
It’s important to know your plants and their needs well before tossing in the first fertilizer you come across.
The key is to know your crop, how it’s doing in terms of nutrient health, and what it needs to thrive.