Magnesium (Mg) Nutrient Deficiencies In Plants

Magnesium deficiencies are often present in soil and water, and it becomes necessary to supplement with additional magnesium amendments.

Magnesium (Mg) Nutrient Deficiencies In Plants

Magnesium is one of the essential mineral nutrients taken up through a plant’s root system from its growing medium, in both soil and hydroponic growing systems.

Oftentimes, not enough magnesium is present in the soil or water, and it becomes necessary to supplement with additional magnesium.

Why Is Magnesium Important For Plants?

Magnesium plays an important role in the health of our plants. It is one of the key components in how our plants convert the energy from its light sources into energy to grow and thrive.

Magnesium is one of the vital nutrients needed for optimal chlorophyll health. Chlorophyll gives the green pigment found in all plant leaves, that enables the plant to absorb and convert energy from light into useful sugars, enzymes, and carbohydrates to grow.

Identifying Magnesium Deficiency In Plants

A magnesium deficiency can be diagnosed by examining our plant leaves. The great news is, a magnesium deficiency is easily identifiable. When plants aren’t receiving sufficient amounts of magnesium at their roots, they will begin to degrade the chlorophyll in the oldest leaves first.

This is a condition called chlorosis, in which the leaves begin to look yellow, yellow-white, pale, and have a marbled, striped appearance between the leaf veins.

This process will often start in the lower regions of the plant first. As deficiencies persist, leaves will begin to curl under and die off.

  • Yellowing of older leaves first between veins
  • Leaf curl over
  • Leaf necrosis


Examples Of Magnesium Deficiency



Magnesium is a mobile nutrient, wherein in can move around, and it is at this point that the plant is breaking down the chlorophyll in the old leaves, in order to transport it to the fresh, young leaves.

If left unchecked, the plant will become completely depleted of its magnesium reserves and will eventually die.

How To Correct Magnesium Deficiency

One of the ways to provide plants the magnesium they need is through the use of organic compost mulch and teas. When compost solutions are applied at the roots, the much needed magnesium in the compost will be taken up by the plant’s roots to be put to work where it’s needed.

Another way gardeners and growers improve the magnesium content is through the use of Epsom salt. Epsom salt is made up of magnesium and sulfur, and it helps to improve the creation of chlorophyll, which again is essential to a plant’s health.

Dilute Epsom salt in water, about 2 tsp/gallon, and apply it to the plants. Apply at both at the roots and as a foliar spray. For best results, spray the leaves with a 2% solution of Epsom salt. Continue this process until all signs of deficiency disappear.

Another solution is to apply dolomite limestone. Dolomite limestone is made up of calcium and magnesium, and provides much of the same benefits as Epsom salt.

Adjusting soil pH above 6.5 or hydroponic water pH above 5.5 while reducing EC for up to a week will also improve nutrient uptake.


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Oftentimes signs of a magnesium deficiency can signify deficiencies in other minerals and nutrients. Many gardeners and growers like to have a Cal Mag supplement on hand in case any of these deficiencies appear.

All-in-one combined solutions give plants the added mineral and nutrition boost that they need. This will result in enhanced foliage growth and healthier fruits and blooms.

Is It Possible To Over Fertilize With Magnesium?

Toxicity is rare and very difficult to see with the naked eye. In extreme cases, overfeeding often creates a conflict with other ions such as calcium. This is especially true in hydroponic solutions. Toxic buildup in soil is very uncommon.

Now that you know the benefits of monitoring the magnesium content in your soil and hydroponic growing systems, and what to do when you spot a deficiency, you can be sure to have the necessary tools on hand to keep your plants at their best.


Want to learn more about nutrient deficiencies?

Read our entire nutrient deficiency series as well as learning about micro vs macronutrients.

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