Magnesium Deficiency in Cannabis Plants: Causes, Symptoms, Effects, and Solutions for Soil and Hydroponics

Magnesium Deficiency in Cannabis Plants: Causes, Symptoms, Effects, and Solutions for Soil and Hydroponics

Magnesium Deficiency in Cannabis Plants: Causes, Symptoms, Effects, and Solutions for Soil and Hydroponics

Magnesium (Mg) is an essential nutrient for cannabis plants, playing a crucial role in their growth, development, and overall health. However, a deficiency in this vital element can lead to a variety of issues, affecting the plant’s overall performance and yield. In this article, we will discuss the causes, appearance, effects, and remedies for magnesium deficiency in cannabis plants grown in both soil and hydroponic systems.

Causes of Magnesium Deficiency in Cannabis Plants

Insufficient magnesium supply:

A lack of magnesium in the growing medium is the primary cause of deficiency. This can occur in soil or hydroponic systems with inadequate nutrient levels or poorly balanced fertilizers.

High pH levels:

In both soil and hydroponic systems, high pH levels can reduce the availability of magnesium to the plant, even if the element is present in sufficient quantities.

Excessive calcium or potassium:

High levels of calcium or potassium can compete with magnesium for uptake by plant roots, potentially leading to a deficiency.

Poor root health:

Damaged or unhealthy roots can reduce the plant’s ability to take up magnesium from the growing medium.

Appearance of Magnesium Deficiency in Cannabis Plants

The following are common symptoms of magnesium deficiency in cannabis plants:

Interveinal chlorosis:

The most noticeable sign is yellowing between the veins of older leaves, while the veins themselves remain green.

Leaf curling:

The affected leaves may begin to curl upward, starting from the leaf margins.

Leaf spots:

Brown, rusty spots may appear on the affected leaves as the deficiency progresses.


Severe magnesium deficiency can lead to leaf tissue death and eventual leaf drop.

Effects of Magnesium Deficiency in Cannabis Plants

Magnesium deficiency can have significant effects on the overall health and productivity of cannabis plants:

Reduced photosynthesis: Magnesium is a crucial component of chlorophyll, the pigment responsible for photosynthesis. A deficiency can impair the plant’s ability to produce energy from sunlight.

Stunted growth:

Magnesium is vital for the production of plant proteins and enzymes. A deficiency can slow down cell division and overall growth.

Reduced yield:

As magnesium deficiency progresses, the plant’s overall health declines, which can result in lower flower production and reduced yield.

Susceptibility to diseases:

Weakened plants are more prone to pests and diseases, which can further reduce the plant’s overall health and productivity.

How to Fix Magnesium Deficiency in Cannabis Plants

Fixing magnesium deficiency requires addressing the underlying cause and supplementing the plant with the required nutrient. The following methods can be used to correct magnesium deficiency in both soil and hydroponic systems:

Adjust pH levels:

Ensure that the pH levels in the growing medium are within the optimal range for cannabis plants (6.0-7.0 for soil, 5.5-6.5 for hydroponics). This ensures that magnesium and other nutrients are available for uptake by the plant roots.

Supplement with magnesium:

Add magnesium to the growing medium or nutrient solution to correct the deficiency. For soil-grown plants, apply magnesium sulfate (Epsom salt) or a magnesium-containing fertilizer. For hydroponic systems, add a magnesium-containing nutrient solution to the reservoir.

Correct calcium or potassium levels:

If excessive calcium or potassium is the cause of the deficiency, adjust the levels by either reducing the amount of these nutrients or increasing the magnesium content.

Improve root health:

Ensure that the roots are healthy and functioning properly by maintaining optimal moisture levels, providing proper aeration, and avoiding root damage during transplantation or maintenance.

Monitor and maintain nutrient levels:

Regularly check and adjust nutrient levels in the growing medium or hydroponic system to ensure a well-balanced nutrient profile. This helps prevent magnesium deficiency and other nutrient-related issues.

Flush the growing medium:

In case of nutrient lockout, flush the growing medium with clean water to remove excess nutrients and salts. This can help restore the plant’s ability to absorb magnesium and other essential elements.

Apply foliar sprays:

In cases of severe magnesium deficiency, a foliar spray of magnesium sulfate solution (1-2 teaspoons of Epsom salt per gallon of water) can provide a quick fix. Apply the spray during the early morning or late evening to avoid leaf burn from sunlight.

Preventing Magnesium Deficiency in Cannabis Plants

Prevention is always better than cure. To prevent magnesium deficiency in your cannabis plants, follow these guidelines:

Use high-quality fertilizers: Select fertilizers specifically designed for cannabis plants with a balanced nutrient profile, including sufficient magnesium.

Regularly monitor pH levels:

Maintain optimal pH levels in the growing medium or hydroponic system to ensure the availability of magnesium and other nutrients.

Practice proper watering techniques:

Overwatering and underwatering can lead to root issues, which in turn can cause nutrient deficiencies. Follow proper watering practices to keep your cannabis plants healthy.

Maintain a balanced nutrient profile:

Ensure that your plants receive an adequate supply of all essential nutrients, and avoid overloading them with excessive amounts of calcium, potassium, or other elements that can lead to magnesium deficiency.


Magnesium deficiency in cannabis plants can lead to a host of issues, ranging from reduced photosynthesis to poor yield. By understanding the causes, symptoms, and effects of magnesium deficiency and implementing the appropriate corrective measures, growers can ensure the overall health and productivity of their cannabis plants. Regular monitoring of pH levels, using high-quality fertilizers, and maintaining proper watering techniques are essential steps in preventing magnesium deficiency and ensuring a successful cannabis cultivation experience.

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