Cannabis Magnesium Deficiency – What Causes It, How To Spot It And How To Fix It

Last updated: 12 July 2020

magnesium deficiency in cannabis plants

Are you noticing your leaves beginning to turn yellow between their veins on lower, older growth? Red stems connecting your fan leaves to your stems, or red streaks running through your plants’ stalks? If so, your weed plants may be facing a potentially deadly nutrient ailment called magnesium deficiency. But why do plants even need magnesium, and how can you solve the problem? You can find answers to these questions and more in this article.

Magnesium’s Role In Cannabis Plants

While magnesium may not be one of cannabis’ three essential macronutrients (nitrogen, potassium and phosphorus), it’s a vital secondary nutrient. However, despite its importance, new growers may find themselves wondering, “what does magnesium do for my plants?” A lot, actually. Magnesium is essential for plants to perform photosynthesis and convert light into energy. As a result, if your weed is experiencing magnesium deficiency, it will slowly wither and starve regardless of the amount of light it gets.

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Precursors And Risk Factors

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First and foremost, growers at risk of facing magnesium deficiency are those who opt for alternative growing media such as coco coir. There are plenty of terrific qualities to this medium, but one undesirable trait is the difficulty it has in absorbing micronutrients like magnesium. Hydroponic growers also need to stay vigilant. They may notice magnesium deficiency in their cannabis gardens as a result of pH imbalances. If the pH of a hydroponic grow dips below 5.0, its plants won’t be able to uptake magnesium regardless of how much the grower adds.

Symptoms Of Magnesium Deficiency

Signs and symptoms of magnesium deficiency

Magnesium deficiency can sometimes be difficult for a new grower to diagnose. That’s because early stages of magnesium deficiency in cannabis share symptoms with other nutrient issues such as nutrient burn. Both nutrient burn and magnesium deficiency present themselves in yellow, crispy leaves. However, while the former starts on the tips of a plant’s leaves, magnesium deficiency begins in lower, older growth. If left untreated, magnesium deficiency will eventually spread out across the entire plant. It may also cause brown spots to appear on the surface of your plants’ leaves.

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How To Solve Magnesium Deficiency

Now that you understand how crucial magnesium is and what magnesium deficiency looks like, you need to learn how to fix it in your plants. There are two paths you can take: flushing and adding supplements, or flushing and changing your nutrients. The next question you may ask yourself is, “how long does it take to correct magnesium deficiency?” Don’t worry – your plants will bounce back in a few days.

Flush And Add Supplements

magnesium deficiency how to solve it

To solve magnesium deficiency, start with a flush of water at 6.0 pH. Then, prepare your normal nutrient mix and add a magnesium supplement. For soil grows, dolomitic lime is a great choice. Hydro growers can use a CalMag supplement instead. Then, adjust the pH of your mix to between 6.0 and 6.5 for soil, 6.0 for coco, and between 5.5 to 6.0 for hydroponic gardens.

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Flush And Upgrade Nutrients

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If you’re using low-quality or piecemeal nutrients, upgrading them may be a better long-term treatment for magnesium deficiency in your plants. You can find specific nutrient lines that are custom-tailored for whatever medium you’re using. Before you feed the new mix to your plants, flush them with water at 6.0 pH. You can then introduce the new line of nutrients.

Prevention Is Key

As with other nutrient problems, the best way to survive magnesium deficiency is to prevent it from occurring in the first place. You can achieve this by feeding only high-quality and cannabis-specific nutrients to your plants. For soil growers, up-potting young plants into a larger container with a time-released fertilizer can also prevent magnesium deficiency from occurring. Don’t let the problem arise and spiral out of control. If you’re astute and diligent, magnesium deficiency will just be a blip in the long-term health of your plants.

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