Everything You Should Know About Growing Cannabis With Calmag

What is calmag?

'Calmag', is a grower's shorthand for referring to fertilizers that supply a plant with additional sources of calcium and magnesium. Calcium and Magnesium are considered secondary macronutrients. This means that a cannabis plant requires greater amounts of Calcium and Magnesium in comparison to micronutrients. Calmag is used in soil, coco and hydroponic applications.

Do I need calmag to grow cannabis?
Calnesium or Organical Magic, are a necessary additive to introduce into your feed schedule. Without one of these supplements your plant is more susceptible to developing a Calcium or Magnesium deficiency.

Think of it this way, beyond the three main macronutrients (nitrogen, phosphorus and potassium), calcium and magnesium are the most vital to cannabis plant health (Secondary Macronutrients). A healthy plant will produce higher yields and better bud than a cannabis plant suffering from malnutrition.

In the wild, plants obtain calcium and magnesium from the earth and water. Soil growers are less reliant on fertilizers as the sole source of nutrition for a cannabis plant and are less likely to require calmag. Some soil growers use Calnesium and Organical magic as a preventative measure against blossom end rot in tomatoes.

Hydroponic growers rely on fertilizers added to water, as the sole source of plant nutrition. Tap water may or may not contain adequate amounts of calcium and magnesium for optimal plant health. Soft water is a term to describe very low mineral content and will likely require calmag supplementation using either Calnesium or Organical Magic. If using reverse osmosis water, one must supplement with calmag, because RO water is completely stripped of any nutritional value for the plant.

The benefits of calmag for cannabis:

Calcium and Magnesium will provide your plant with increased flowers, increased water, nutrient, and carbon dioxide uptake, and increased cell division, plant tissue development, and chlorophyll production.

You can use calnesium or organical magic throughout your plant’s entire life cycle during rooting, vegetative growth, and flowering. It can be used as a foliar spray as well and can be given to your plant every feeding.

Both Organical Magic and Calnesium can be used in any grow medium: soil, coco, hydroponics, aeroponics, etc.

How much calmag do I need?

How much calmag your plant will need will be dependent on a few factors: strain, type of water used, water PPM, growing medium, etc. For example, someone growing in nutrient rich tap water may need little-to-no extra calmag even when growing in coco. Others may need to add it at full strength. Every plant is different, so we recommend tweaking our feed schedule to ensure you find the right balance for your plant. In general, we recommend 1.5-5mL per 1 gallon of water. Commonly, coco growers will require more calmag than soil growers.

Why is calcium essential for growing cannabis?

Just like humans require calcium to build and maintain our skeletal structure, plants require calcium to fortify cell walls to increase structural integrity. Calcium is responsible for developing strong and rigid cell walls that make strong plant tissues. Cell walls also function to transport nutrients through the plant where they are needed. Calcium is crucially important in the cell division process, which determines a plant's growth.

How to identify a calcium deficiency in cannabis:

Calmag Deficiency Foliar Spray Recipe: Calnesium and Super B+

Calcium deficiencies will appear on leaves that are either new or still growing. Dark spots on new or growing leaves. Older leaves may die, and new leaves will be stunted or distorted. Leaf tips may curl, and brown spots will develop.

Why is magnesium essential for growing cannabis?

Chlorophyll is the green pigment that gives foliage its colour. Chlorophyll is essential for photosynthesis to absorb light energy and turn it into carbohydrates that a plant can then use as food. Without magnesium a plant would be unable to create chlorophyll, rendering photosynthesis impossible.

Magnesium acts as an ionic glue in the center of the chlorophyll molecule, stabilizing it for photosynthetic functions to take place. Magnesium also aids in the nutrient transport and absorption of other nutrients like phosphorus and iron.

Future Harvest Organical Magic and Calnesium lay atop a pile of strengthened and stress relieved cannabis buds

How to identify a magnesium deficiency:

Magnesium deficiencies are common in soils with a low pH (7 or lower). Lower leaves will turn yellow and eventually dark green. Eventually, as the deficiency worsens, younger leaves will begin to be affected. After a while, the leaves will curl upwards and fall off.

BOTH calcium and magnesium serve secondary roles in the activation of key enzymes that determine the quality and potency of dried cannabis.

If a calcium/magnesium deficiency is not addressed, it can quickly turn fatal with your plant losing most of its lower leaves. When using nutrients designed for cannabis your plant shouldn’t suffer a calcium magnesium deficiency. However, this can still happen if your pH is out of range. The pH in your plant’s root zone is incredibly important and a pH out of range can cause the roots to not be able to absorb magnesium.

Fun fact:

Farmers use dolomitic lime applied to the soil to adjust pH, which serves to supplement both calcium and magnesium in the process.

Cannabis grower using Future Harvest Calnesium to spray a plant.

Calmag as a foliar spray:

Most yellowing plants are from deficiencies in either nitrogen, magnesium, or iron. Calnesium contains all 3 and applying through foliar feeding will provide these crucial elements while any deficiencies in the root zone are corrected.

Foliar Spray 'Green Up' Recipe:

- 2 ml of Calnesium (Can be substituted for Organical Magic but you will lose the nitrogen boost)
- 1 ml of Super B+
Get your Organical Magic or Calnesium today! 

Like this article? For more information on cannabis cultivation check out our blog!


 ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀OMRI certified Future Harvest bottles stand in the middle of a pathway of healthy plants.




Any questions? Email us at marketing@futureharvest.com or send us a message on Instagram @futureharvestdevelopment and we will help you as best we can!

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    Published by Future Harvest

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  • Nov 15, 2022
  • Category: Articles
  • Comment: 1
1 Comment
Bud dog October 13, 2021

Do you mix silica and calnesium first before future harvest base nutrients ?

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