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Solving Manganese Deficiency in Cannabis

Manganese deficiency cannabis

What Does Manganese Do for Cannabis Plants?

Manganese Deficiency Cannabis is a problem you should fix right away because, despite being a micronutrient, Manganese plays a crucial role in the health of your cannabis plants. It is vital for chlorophyll production, which makes photosynthesis possible, and disintegrates enzymes.

Manganese ensures that nitrates are available for your plants to use during protein production by helping the plants absorb nitrogen. Additionally, it strengthens the roots of your plants and promotes the growth of pollen tubes, which makes pollen production possible.

How to Identify Manganese Deficiency in Cannabis

Generally, Manganese Deficiency Cannabis is quite rare and usually only happens when iron and zinc are also in low supply. You will know your cannabis plants are manganese deficient when the leaves turn yellow, rapidly degenerate, then finally turn brown. The symptoms are usually confined to fresh, new leaves and are often misdiagnosed because of the rarity of manganese deficiency.

It could take a lot of time to correctly diagnose Manganese Deficiency Cannabis – even as long as several weeks. If you are not fast to act, your cannabis plants might not last this long and, by then, all of the upper leaves will be discolored, wilted, and brown. Here are the symptoms you should watch out for:

Common Symptoms of Manganese Deficiency


Most symptoms of Cannabis Manganese Deficiency will show up on the leaves. Expect the foliage to turn yellow between the veins and produce brown, mottled spots or patches where the cells are dead. Over time, the spots might spread and kill the entire leaf. The changes will usually begin at the base of the leaves and extend toward the tips. You might see:

Cannabis Manganese deficient leaf
A comparison of Manganese deficient cannabis leaf versus a healthy one
  • Pale leaves that turn yellow with time
  • New foliage comes out yellow
  • Yellowing between the leaf veins
  • Brown spots that spread and kill the leaf
  • Patches of speckles
  • Reduced foliage growth


The root system remains small and unhealthy due to the plant’s inability to photosynthesize.

Abnormal Plant Growth

  • Stunted growth
  • Abnormal development
  • Lower than usual yields

What Causes Manganese Deficiency in Cannabis Plants?

There are many potential causes for Manganese Deficiency Cannabis. You might be feeding your cannabis plants insufficient nutrients or the plants might be unable to absorb the nutrients efficiently. Generally, an inability to absorb manganese can be caused by overwatering or clogged soil. When the soil compacts, it can become difficult for the roots to absorb nutrients from the water or soil.

Alternatively, your cannabis plants might be facing nutrient lock due to an imbalanced pH, which is the most common cause of many deficiency problems. Cannabis plants need to be grown at neutral pH to be able to absorb the available manganese. For soil, the ideal pH is between 6.0 and 6.5 while a pH of around 5.5 to 6.0 is acceptable for coco air and hydro setups.

If you are growing in soil, check that your pots are well-drained and no water is sitting around the roots. This will ensure your cannabis plants absorb manganese, preventing Manganese Deficiency Cannabis.

How Do You Solve Cannabis Manganese Deficiency?

If you have studied the symptoms and believe your plants are suffering from Cannabis Manganese Deficiency, you should immediately flush your grow medium with fresh, clean pH’d water containing cannabis-friendly nutrients. The dose should be regular and include manganese.

By flushing the growth medium, you will eliminate extra nutrient salts and iron that might be causing manganese lockout. You will also neutralize the pH, which allows for proper manganese absorption, as well as supply your cannabis plants with the manganese nutrients they are missing.

It is important to note that some symptoms of Manganese Deficiency in Cannabis like the brown leaves will not go away with treatment. If your cannabis plants are still in the vegetative stage, consider topping them with fertilizer to replenish manganese levels. However, if they have already entered the flowering stage, you will have to prune out the affected foliage.

Tip: Never prune all the leaves from your cannabis plants at once as leaving them completely bare all of a sudden can be stressful. Instead, prune in stages.

Leaving brown, dead leaves on your cannabis plants will do more harm than good for your garden. Because they will never recover, the problem might spread to and kill the rest of the plant or the leaves could attract pathogens and diseases to the garden.

Once you flush and feed your cannabis plants, you should begin to note improvements in the new foliage. New leaves and shoots will come out green and healthy although the older, already-affected ones will remain the same. When the new leaves come in, you should remove the affected ones so that the nutrients you have provided get directed to the new shoots.

If, after a few weeks, there are no improvements, you should give your plants a manganese chelate.

Plant Problems with Similar Symptoms to Manganese Deficiency

Because Manganese Deficiency Cannabis is very rare, it is easy to mistake it for iron deficiency. This can lead to more problems because treating your cannabis plants for iron deficiency when they have manganese deficiency could make the latter worse. This is because an excess of iron in the soil or growing medium will lockout manganese and prevent efficient absorption.

One way to differentiate manganese deficiency from iron deficiency is to study the yellowing of the leaves. With Manganese Deficiency in Cannabis, the leaves turn more yellow while the margins around the leaf veins remain dark green. The yellowing will usually begin at the bottom and spread to the tips.

Manganese deficiency also causes spots on leaves, which is also a symptom of calcium deficiency. For this, you will have to rely on the other symptoms of both deficiencies to diagnose your plants.

Check out our guide on all the cannabis deficiencies for more information.

Final Word on Manganese Deficiency

If left untreated, Manganese Deficiency Cannabis can kill your plants and leave you with no harvest to show for your efforts. If you suspect your cannabis plants are suffering from manganese deficiency, this guide should help you diagnose and treat the problem immediately.

The best way to avoid or treat this problem is to maintain the growth medium and water at a neutral pH level. You should also feed your plants with high-quality cultivation substrates and nutrient lines that are able to self-correct to the ideal pH level for your substrates.

Picture of Ed Rushford

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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