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A clear explanation of Cannabis nutrition can open doors for growers to be more hands on with their Cannabis plants. When growing Cannabis understanding the plants requirements at each stage can be the difference between a vibrant healthy plant and one that is showing signs of a serious nutrient deficiency. Experienced growers understand that nutrition affects the final taste, aroma and experience of smoking the flowers. Here you will learn about Cannabis nutrition and which feeds to use during different Cannabis plant stages. We also explain the final flush and how to deal with common nutrient related problems with Cannabis cultivation.

What Does N-P-K Mean?

cannabis nutrition

Cannabis nutrition for growth and flowering phases by Grotek. Fertilizer companies often provide an easily outlined nutrition plan for both the vegetative and flowering phase. The N-P-K values will always be displayed on the packaging, in this case you can see that the Monster Grow Pro package is marked with 18-36-1.

You will see these three letters on any liquid feed, bag of medium, organic and often on commercial bags of soil. These three letters represent nitrogen (N), phosphorus (P) and potassium (K) which are the three main macronutrients plants need. During early growth and the vegging stage, Cannabis plants will grow as a shrub and will need nitrogen to keep photosynthesis going in green leaves in order to produce sugars. Cannabis nutrition during flowering also requires phosphorus for stem development and potassium to increase flowering sites. During their entire life cycle Cannabis plants will absorb the nutrients they need next. It is therefore important to have a readily available source of these three main elements accessible for your plants. Most soil growers prepare their soil so that it provides plenty of nutrients, but it can be very beneficial to also incorporate fertilizers intended for Cannabis nutrition.

Micro And Macro Nutrients

Micronutrients and the remaining macronutrients are often overlooked by growers. These are the small vitamins and minerals that plants require for their metabolism, they are essential for a plant’s survival but are required in much smaller amounts than nitrogen, phosphorus and sodium. These minerals are calcium, magnesium, boron, copper, zinc and sodium. Calcium, magnesium and sodium are considered to be the other three macronutrients. Boron, copper and zinc are considered to be the most important micronutrients. A full complement of these macro- and micronutrients is essential for healthy Cannabis nutrition.

micro and macro cannabis nutrition

Mineral elements required by plants. This picture shows an overview of all the different nutrients that Cannabis plants require during their life cycle. While Cannabis nutrition often focuses on N, P and K because these are used in the greatest quantities, it is important to remember that all of these nutrients are essential.

Organic Medium

It is a good idea to have an organic medium which will slowly break down over time, releasing readily available nitrogen, phosphorus and potassium into the medium as well as supplying the plants with all the micronutrients they need. Below is a list of possible organic feeds to use along with an explanation of their relevance in the garden.

Nutrition For Seedlings

From the point a Cannabis seed is dropped into a glass of water, or placed in a dark warm wet place all it really needs is water. After the seedling has begun to grow and push itself above the soil, you should consider a soft feed like worm castings. Mixing this with perlite will aid aeration of the medium. Seedlings mainly require phosphorus for root development and nitrogen to grow thick lush green leaves. Calcium is used throughout the life cycle in the synthesis of cell walls, allowing a plant to grow. Magnesium forms the central molecule in chlorophyll, which means that it is required for photosynthesis throughout the life cycle of the plant.

Nutrients Required For Seedlings: Nitrogen (N) Phosphorus (P) Calcium (Ca) Magnesium (Mg)

Recommended N-P-K values of nutrients for seedlings: 2-1-2

Cannabis Nutrition For Vegetative Phase

This is what most growers consider the real growing part, so here the plants require all macronutrients. Plants will produce many shoots, stems, leaves and plenty of roots at this important stage. Cannabis nutrition during the vegetative phase should contain mostly nitrogen, phosphorus and some potassium.

Nutrients Required Vegetative Phase: Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg)

Recommended N-P-K values of nutrients during growth phase: 10-5-7

Cannabis Nutrition For Flowering Phase

A good piece of advice when transitioning to the flowering phase is to also gradually transition to your flowering nutrients. This means that you will use a further diluted solution, or one that is partially still your vegging solution the first few times you feed your plants during flowering. A gradual transition will help to avoid shocking your Cannabis plant.Nutrient companies sell seperate veg feed and bloom feed, but these are not as different as you might think. Both usually contain the same nutrients, be it in different ratios. Plants will still produce as many leaves during the flowering phase as they did during the vegging phase.

Nutrients Required Flowering Phase: Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg)

Recommended N-P-K values of nutrients during flowering phase: 4-15-10

Cannabis Nutrition For Flush Phase

The final flush period is to clear out any salts that may have built up over the numerous feeds. Not only will this improve the way the buds taste, burn and even smell but it will also push the plant during the last stages before harvest. A flush means to totally wash away any remaining leftovers. Use only water during this stage and let the plant do the rest of the work. If you can flush for a period of 10-14 days then for sure your ash will be a soft grey and the joint should continue to burn once lit.

Nutrients Required: Strictly water. Distilled, tap, carbonated and R/O water also work fine.

Below is a list of soil amendments and fertilizers that are commonly used to provide nutrition for Marijuana plants, these amendments and fertilizers can all be sourced locally and used safely for long periods of time.

Worm Castings: Essentially what worms excrete after eating soil. This substrate is not only very soft and easy to work with, it is very high in nitrogen, calcium and magnesium. The excrement has been breaking down over time, hence the colour is a dark black. Worm castings can aid Cannabis nutrition over a long period of time as the nutrients inside are released slowly.


Worm Humus, Also know as vermicast or vermicompost, worm humus is decomposed material excreted by the earthworm. Adding worm castings to a substrate mixture provides your plants with a slow releasing source of several essential nutrients.

It is usually easy to buy worm castings locally, but it can also be bought from many different nutrient companies.

Bat Guano: There are different types of bat guano depending on what the food source was for the bats, this also determines the NPK ratio. Generally bat guano is high in phosphorus and low in nitrogen and potassium. Roots require large amounts of phosphorus to grow during all stages of plant development. Phosphorus becomes even more important during flowering as plants consume large amounts of phosphorus and potassium during this stage.

Plagron Bat Guano Soil Amendments

Bat guano varies in N-P-K value, but always has a high amount of P.

Horse Manure: The average NPK values of horse manure or any animal manure are usually very low. Usually manure tests at NPK levels of 1-0.5-0.8, so horse manure has more merit as a soil additive rather than a main source of base nutrients. Manure is also great for making organic compost tea which can improve Cannabis nutrition and the final taste of the flower. Fresh horse manure is usually cheap and available from local sources like farms. Dry horse manure granulate also exists and is easier to use, but much harder to find.

Horse manure. Horse owners are often happy to sell their manure as they have a steady supply coming in and usually only limited space for storage.

Organic Liquid Feed: Using organic liquid feeds can be highly beneficial and can complement an organic medium very well. Many organic feeds will be algae, molasses or mineral based. Organic feed usually contains slow releasing nutrients that are absorbed and used by plants as required. Cannabis nutrition during flowering can be provided through homemade compost teas, which can easily be made by using the soil amendments above.

Organic compost teas can be extremely beneficial to the plant and can help prevent and even resolve many Cannabis nutrition problems you may experience. The billions of beneficial bacteria inside a compost tea form a symbiotic relationship with a Cannabis plant, allowing both to use nutrients more efficiently and grow faster. Check out our blog for a step by step guide to making your own organic compost tea.

organic cannabis nutrient

Organic Cannabis Nutrients. This organic nutrient line is based on algae and is produced from 100% renewable sources, making this product very environment-friendly.

Hydroponic Liquid Feeds: The size of the nutrient molecules available to the plants roots when using hydroponic feed is totally different than when using organic nutrients. Hydroponic feeds focus on delivering smaller chelates that can be absorbed more readily from the constant supply of nutrient solution rather than releasing nutrients slowly. Using organic feeds in a hydroponic system will cause massive problems for both the actual system and then the plant itself. Most nutrient companies offer hydroponic nutrients in a two- or three part product.
organic cannabis nutrition for hydroponic grows

Organic Cannabis Nutrients. This organic nutrient line is based on algae and is produced from 100% renewable sources, making this product very environment-friendly.

By following the guidelines in this article, you should be able to improve your yield already. Most of all, we hope to have improved your understanding of what nutrients your plants need and how to provide them, so that the difficult subject of Cannabis nutrition can become as easy as watering your plants