The importance of Cal-Mag (Calcium & Magnesium)

The importance of Cal-Mag (Calcium & Magnesium)

Calcium (Cal) - Symbol: Ca

Calcium is responsible for maintaining strong cell structure and vigour.

High calcium levels are vital during the late growth stage, as additional calcium will ensure a higher number of flowers are produced and retained by the plant. This is particularly important if you want those flowers to transition into the fruiting stage. If a plant lacks calcium stores, the plant will not be able to complete regular development and growth will be stunted.

Calcium also plays a critical metabolic role in the removal of carbohydrates, while also neutralising cell acids.

Some other benefits include:

  • Promotes plant cell elongation
  • Strengthens the structure of the cell wall through the formation of calcium pectate compounds.
  • This will bind cells together and give stability to the cell walls.
  • In doing this, calcium will protect the plant against diseases, as stronger cell walls will make it harder for fungi and bacteria to break through
  • Assists with hormonal and enzymatic processes
  • Improves fruit quality


What Happens When Plants Become Calcium Deficient?

Calcium deficiencies in plants are usually a result of low calcium availability, or water stress that lowers transpiration rates. 

You can usually tell if a plant has become deficient in calcium if young leaves start to curl or have spots appear on them. Stunted growth, leaf tip burns and aborted flowers or damaged fruit are other signs that your plant isn’t getting enough calcium.

Another variable to consider when observing a calcium deficiency is pH. If the pH of your nutrient solution is not in the desired range, then calcium can become unavailable to the plant, always ensure to check & correct pH. Calcium becomes difficult for most plants to absorb at a pH below 5.5, almost exactly the same as range Magnesium


Magnesium (Mag) - Symbol: Mg

Magnesium is a key element (core atom) in the production of chlorophyll, plants leaves/leaflets would not be able to form a ‘complete’ green pigment without magnesium’s presence. It has a relationship with calcium which directly impacts water hardness (pH) it is used by every plant cell and without it photosynthesis would not occur.


How do you recognize a Magnesium (Mg) deficiency?

Observation of older leaf growth.

Magnesium displays itself as a pale-yellow fading or blotching almost freckle/spot like in appearance. Limey/yellow ‘cells’ indicates the depletion of chlorophyll in that cell of which magnesium is responsible for.

Usually when magnesium is unavailable the deficiency is often displayed alongside calcium (orange rusty freckles/spots). Most commonly growers add ‘Cal/mag’ amendments, which are fine to use if nutrition has been poor and the plant is underfed however in most cases simply adjusting the pH of the nutrient solution will make this element in range for the plant to absorb.

  • Magnesium deficiency is pale yellow blotching (Cell pigment depletion)
  • Magnesium deficiency sometimes shows with Calcium deficiencies
  • Magnesium deficiency can occur when K and Cal are being used in excess

Magnesium deficiency can happen quickly when growers start first switch to high intensity LED lighting, forcing a higher rate of photosynthesis which Magnesium plays a key role in. If the grower does not adjust the feed strength of the nutrient solution when switching to LED lighting, it's quite common to see magnesium deficiencies appear within a week or so if nutrition is not increased to match the new light levels.

Cal-Mag product recommendations:

We stock several products that can be used as a Cal-Mag supplement to boost your Ca/Mg supply.


HY-GEN Humiboosta

HY-GEN HumiboostaThis product is a solid all round product we highly recommend to all growers for all stages of growth. HY-GEN's Humiboosta is a humic/fulvic acids supplement with calcium and magnesium and all trace elements, aiding your plants in much more ways than just Cal-Mag supplementation.


FlairForm CMX

FlairForm CMXCMX is a strong Calcium, Magnesium and Iron supplement with nitrogen that aids growers who are in need of a stronger Cal-Mag to add to their nutrient solution. This product is excellent for heavy calcium or magnesium plants that require much more than typically required. The levels of nitrogen in this product also make this an excellent product for early stage development.


CYCO Dr. Repair

CYCO Dr RepairCYCO have a large range of additives in their platinum series nutrients, Dr.Repair is there Cal-Mag supplement, also with additional nitrogen for starving plants. Although it's not directly listed on the bottle, Dr.Repair is a great Cal-Mag product that is designed to boost under-fed plants back to health.





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