Nutrients to grow a healthy Cannabis plant

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Cannabis Nutrients – Macro and Micro Nutrients thumbnail

What kind of nutrients does Cannabis need to grow?

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In today’s article we’re going to cover the different nutrients that cannabis needs to grow.
We’ll look at macro-nutrients, micro-nutrients (aka trace elements). For each element we will mainly focus on their use, their mobility and importance.

Macro and Micro Nutrients for Cannabis - Table of content

Macro Nutrients for Cannabis

“Macro-nutrients” is a term that regroups 3 nutrients necessary for a healthy plant. All of these are mobile, which means that the plant can reallocate them from one part to another.

For example, it needs some Nitrogen to grow new foliage. The plant can take the Nitrogen from lower leaves and reallocate it to this new growth. While doing so you will notice the older leaves turning yellow. The typical sign of Nitrogen deficiency

The 3 macro nutrients are:

Nitrogen (N)

Marijuana looooves Nitrogen and requires high levels of it during the vegetative stage. Once you get into the flowering stage its need drops drastically. You’ll understand quickly why in the “purpose” section.
Nitrogen is a nutrient that easily washes away from the soil. It needs to be replaced regularly, especially during vegetative growth.

If there’s an excess of Nitrogen when harvesting the plant the buds won’t have as good of a taste and won’t burn well. This is one of the reasons why it’s important to flush well your plants before the harvest.

The Purpose of Nitrogen

Nitrogen regulates the cannabis’s ability to make proteins. These proteins are essential for new protoplasm in the cells.

Nitrogen allows the plant to tie proteins, hormones, chlorophyll, vitamins and enzymes together.
It is also essential for the production amino acids, enzymes, nucleic acids, chlorophyll and alkaloids.

This important nutrient is mainly responsible for leaf and stem growth as well as overall size and vigor.

Nitrogen is most active in young buds, shoots and leaves. Ammonium (NH4+) is the most readily available form of nitrogen.
If you use this, be careful not to use too much since it can easily burn the plants.

The Nitrate form of nitrogen is much slower to assimilate than ammonium. As such, it will release much slower in the soil. Hydroponic fertilizers use this slower-acting nitrogen compound and mix it with ammonium.

Phosphorus (P)

Cannabis uses the phosphorus during all stages of it life and has a different purposes at each stage.
During the vegetative stage, it’s mainly used for root development. On the other hand during the flowering stage one of its uses is bud growth.
Phosphorus is one of those extremely important nutrients.

Just like Nitrogen, Phosphorus is a Mobile element. This means that the plant can reallocate it where ever it’s needed

Purpose of Phosphorus

Phosphorus is necessary for photosynthesis. It also provides a mechanism for the plant to transfer energy within itself.

It’s also one of the components of DNA and is associated with overall vigor, resin and seed production.

The highest concentrations of Phosphorus are found in the root-growing tips, growing shoots and vascular tissue.

Potassium (K)

Potassium is used at all stages of growth. Soils with a high level of potassium increase a plant’s resistance to bacteria and mold.

Purpose of Potassium

Potassium helps combine sugars, starches and carbohydrates. These combinations are essential for growth by cell division.
It also increases the chlorophyll in the foliage and helps to regulate the stomata openings. This allows plants to make better use of the light and air.

Potassium is essential in the accumulation and translocation of carbohydrates. Furthermore, it’s necessary to make the proteins that increase the oil content and improve the flavor in cannabis plants.

And finally, Potassium encourages strong root growth, it is associated with disease resistance and.. water intake.

So yeah, also a pretty important nutrient 🙂

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Secondary Nutrients

Secondary nutrients are also used by the plants in large amounts. Although the term “secondary” is in the name, it does not mean that they aren’t important.
If these nutrients aren’t available to your plant you will see issues.

Here are the main secondary nutrients and their uses:

Magnesium (Mg)

Magnesium is a mobile nutrient used a loooot and deficiencies are common. Especially so in acidic soils.

If you’re experiencing this, you can add some dolomite lime your acidic potting soils. Doing this before planting can stabilize the pH, as well as add magnesium and calcium to the soil.

If you have a deficiency and did not do this, you can add Epsom Salts with each watering. This should correct magnesium deficiencies.
Use Epsom Salts designed specifically for plants rather than the supermarket-type in order to ensure the quality.

Purpose of Magnesium

Magnesium is found as a central atom in every chlorophyll molecule. It is essential for the absorption of light energy.

Magnesium also aids in the utilization of nutrients. Its enzymes make carbohydrates and sugars that are later transformed into flowers.
Finally, it also neutralizes the soil acids and toxic compounds produced by the plant.

Calcium (Ca)

Calcium is an immobile nutrient, this means that the plant cannot reallocate it if it has a deficiency. In case of a deficiency, newer growth will be affected.

Cannabis requires nearly as much calcium as all other macronutrients.
To help avoid deficiencies you can add fine dolomite lime to the soil. For hydro lovers, you can use soluble-hydroponic fertilizers containing adequate calcium levels.

Purposes of Calcium

Calcium is fundamental to cell manufacturing and growth. It is necessary to preserve membrane permeability and cell integrity, ensuring the proper flow of nitrogen and sugars.

The famous “cell walls” that plant have is composed of calcium, kind of like our bones. Take it out and you have some odd growth going on (check out our article below to see some examples, pretty cool).

Calcium also stimulates enzymes that help build strong cell and root walls. Cannabis plants must have some calcium at the growing tips of each root.

Sulfur (S)

Many fertilizers contain some form of sulfur. For this reason, sulfur deficiency rarely occurs. We’ve read that growers avoid elemental (pure) sulfur in favor of sulfur compounds such as magnesium sulfate. This is due to the fact that nutrients combined with sulfur mix better in water.

Purpose of Sulfur

Sulfure is an essential building block of many hormones and vitamins. It’s also a necessary element in many pant cells and seeds.

Virtually all grounds, river and lake water contain sulfate. Sulfate is involved in protein synthesis, is part of the amino acid, cystine and thiamine. These are the building blocks of proteins.
On top of that, Sulfur is also essential in the formation of oils and flavors, for respiration and synthesis as well as the break down of fatty acids.

Hydroponic fertilizers separate sulfur from calcium in an “A” and “B” container and for good reason.
If you combine these the sulfur and calcium will form crude, insoluble gypsum (calcium sulfate). This will settle as residue to the bottom of the tank and will not be available to your plant.

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Micro Nutrients (aka Trace Elements)

Micronutrients, also called trace elements or trace nutrients, must be present in small amounts.

Their function is mainly to act as catalysts for plants, allowing them to process and utilize other elements.

If you start getting deficiencies related to these, you can use fertilizers designed for hydroponics.

High quality hydroponic fertilizers use food-grade ingredients that are completely soluble and leave no residues.
If you are using an inexpensive fertilizer that does not list a specific analysis for each trace element on the label it’s a good idea to add soluble trace elements in a chelated form.

Chelated micronutrients are available in powdered and liquid forms. Add and thoroughly mix them into the growing medium before planting.

Micronutrients are often already present in commercial potting soils and soilless mixes. Generally you don’t have to worry about them. To be sure, check the ingredients on the bag to make sure that the trace elements were added to the mix.

These elements are necessary in small levels. They can easily reach toxic levels so be careful and always follow the the advertised volumes.

Here are the micro-nutrients were going to cover :

Zinc (Zn)

Zinc is a mobile micro nutrients. Common reasons for its deficiency are arid climates and alkaline soils. For more info on the latter, you can check out our “pH levels for watering“.

What is the purpose of Zinc

Zinc works with manganese and magnesium to promote the same enzyme functions. Zinc cooperates with other elements to help form chlorophyll as well as prevent its demise. It’s an essential catalyst for most plants enzymes and auxins; It’s also crucial for stem growth.
Zinc plays a vital part in sugar and protein production and zinc deficiencies are fairly common in soils with a pH of 7 or more.

Manganese (Mn)

Manganese is an immobile nutrient and deficiency is relatively common indoors.

What is the purpose Manganese

Manganese is engaged in the oxidation-reduction process associated with the photosynthetic electron transport. This element activates many enzymes and plays a fundamental part in the chloroplast membrane system.
Manganese assists nitrogen utilization along with iron in chlorophyll production.

Iron (Fe)

Iron is another immobile element. You can easily purchase it in a soluble chelated form so it is immediately available for absorption by the roots. For indoor growers, deficiency can be common in alkaline soils.

What is the purpose of Iron

Iron is fundamental to the enzymes systems. It is also needed to transport electrons during photosynthesis, respiration and chlorophyll production.
Iron allows plants to use the energy provided by sugars.

It is also a catalyst for chlorophyll production, as well as necessary for nitrate and sulfate reduction and assimilation.

When walking around, you can notice iron rich soils as it colors the earth from brown to red, depending on its concentrations.

It is important to note that plants have a difficult time absorbing iron. Make sure you’re using a chelated form.

Boron (B)

Boron is a immobile nutrient that usually causes no problems. That said, boron must be available during the entire lifecycle of a plant.

What is the use of Boron

Boron is still somewhat a biochemical mystery. We know that boron helps with calcium uptake and numerous plant functions.

Scientists have collected evidence to suggest boron helps with synthesis, a base for the formation of nucleic acid (RNA uracil) formation.
Strong evidence also supports that boron’s role in cell division, differentiation, maturation and respiration as well as a link to pollen germination.

Chlorine-Chloride (Cl)

Chloride is found in many municipal water systems and Cannabis tolerates low levels of it. Usually you won’t find it in regular fertilizers and it is very rare to see deficiencies of it, whether indoors or outdoors.
Chloride is a Immobile nutrient.

How does Cannabis use Chloride

Chlorine, in the form of chloride, is fundamental to photosynthesis and cell division in the roots and the foliage.

It also increases osmotic pressure in the cells, which opens and closes the stomata to regulate moisture flow within the plant tissue.

Cobalt (Co)

This immobile nutrient is rarely mentioned as necessary for plant growth and most fertilize labels don’t include cobalt. Cobalt deficiency virtually never happens indoors.

How does Marijuana use Cobalt

Cobalt is necessary for countless beneficial bacteria to grow and flourish; It’s also vital for nitrogen absorption.

Scientific evidence suggests this element is linked to enzymes needed to form aromatic compounds.

Copper (Cu)

Copper is an immobile nutrient concentrated in the roots for enzymes, it’s also a good fungicide.

How does the Weed plant use Copper

Copper is a component of numerous enzymes and proteins. Necessary in small amounts, copper helps with carbohydrate metabolism, nitrogen fixation and the process of oxygen reduction.

It also helps with the production of proteins and sugars.

Molybdenum (Mb)

Molybdenum is an immobile nutrient that is very, very rarely deficient.

How does the Marijuana use Molybdenum

This trace element is a part of 2 major enzyme systems that convert nitrate to ammonium. This essential element is used by the marijuana plant in very small quantities.

It’s most active in roots and seeds.

Silicon (Si)

Silicon is absorbed by the plants as silicic acid. Its main purpose is to assists in keeping iron and manganese levels consistent.
It will mainly be found in the epidermal cell walls where it collects in the form of hydrated amorphous silica.

Silicon guarantees stronger cell walls. They will better resist pest attacks as well as increase heat and drought tolerance.

Note: Pests and diseases have a difficult time penetrating plants that are sprayed with a silicon-based repellent/insecticide.

Nickel (Ni)

Nickel is used by Enzymes to break down and use the nitrogen; it’s also essential for iron absorption. Nickel deficiency is rare and it’s generally subtly mixed with other nutrients, most commonly nitrogen.

Sodium (Na)

This is one of the problem elements, just a little bit will go a long way! Sodium is taken up by the roots very quickly and in small amounts (50 ppm). It can block enough other nutrients causing severe deficiencies as a result.
When mixed with chlorine, it turns to table salt, which is the worst possible salt to put on the plants.

Be very careful to measure your input water and ensure that it contains less than 50ppm of sodium (the less the better)

Recommended amounts of Nutrients for Cannabis

In the chart Below you’ll find the suggested amounts of soluble-salt fertilizers for indoor growers.

Keep in mind that these amounts will vary depending on the strains and which step of the life cycle your plant is in, as well as which strain she belongs to.
All values are in parts per million (ppm)


Nitrogen (N)150-1000250
Calcium (Ca)100 – 150200
Magnesium50 – 15075
Phosphorus50 – 10080
Potassium100 – 400300
Sulfur200 – 1000400
Copper0.1 – 0.50.5
Boron0.5 – 5.01.0
Iron2.0 – 105.0
Manganese0.5 – 5.02.0
Molubdenum0.01 – 0.050.02
Zinc0.5 – 1.00.5
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Alright folks, that’s it for this one!
If you still have questions, don’t hesitate to reach out 😉

Until next time,
be safe and grow easy

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