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How to Solve Cannabis Manganese Deficiency



More often than not, manganese is plentiful and readily available for uptake by your cannabis plant. However, some conditions such as PH issues in the media or nutrient competition from other nutrients like iron could lead to a cannabis manganese deficiency. If you notice that your cannabis plant has suddenly become unhealthy and doesn’t seem to be getting better, you should explore the possibility that it might be suffering from deficiency of this little known micronutrient. Learn everything you need to know about this often missed micronutrient and know how to recognize and quickly fix a manganese deficiency in your cannabis plants.

What is Manganese?

Manganese forms part of the nine essential nutrients required by plants for growth. Manganese is a fixed micronutrient and does not travel throughout the cannabis plant. Like all micronutrients, magnesium is of capital importance to the healthy growth of cannabis plants. The role manganese plays in plant health is extremely crucial.  It is necessary for numerous processes including photosynthesis, synthesis of some particular enzymes, chloroplast formation, and nitrogen metabolism.

Manganese can have both a limiting factor on cannabis plant growth, as well as a toxic effect if found in excess. Its similarities to iron are notable and its deficiency or toxicity is often confused for those of iron. 

Manganese deficiency in plants is mostly common in soils and other mediums which have a neutral to high pH or those which contain a substantial amount of organic matter. Excess manganese causes nutrient lockout in iron. 

What Does Manganese Do For Your Plants?

The roles manganese plays in the growth and health of cannabis plants are diverse and crucial. It is used by marijuana plants as a major contributor in critical biological processes such respiration, photosynthesis, and nitrogen assimilation. It is also involved in pollen tube growth, pollen germination, and the ability for cannabis plants to resist root pathogens and root cell elongation.

Manganese is also vital in the disintegrating of enzymes as well as creating chlorophyll. In marijuana plants, manganese plays a very important part in ensuring that nitrates are available for the creation of proteins.  Manganese deficiency in marijuana plants does not frequently occur, and when it does, it usually has a connection with the lack of iron or zinc, or pH levels that are unfavorable. 

How do you Identify Cannabis Manganese deficiency? 

When identifying a deficiency in your cannabis plant, it is very important to correctly identify the exact deficiency as a misdiagnosis could lead to even worse consequences. Fortunately, a manganese deficiency is relatively easy to spot in cannabis plants as you will notice the leaves of your cannabis plant will begin to turn yellow as well as signs of interveinal chlorosis. A magnesium deficiency will first affect the new, young leaves as magnesium is an immobile nutrient 

Leaves turn darker

While yellowing occurs mainly along the veins, the leaves of the cannabis plant affected by a marijuana manganese deficiency may remain green. The outside part of the leaves of the marijuana plant may turn a dark green color. This may be especially visible in soils or other mediums that have a high pH, and that should be the first thing that is checked and corrected.

Brown spots on leaves

As the cannabis leaves start to yellow, they also develop brown spots. The first signs of a manganese deficiency will appear in the stems of the leaves, through the veins and working their way towards the tips of each leaf. As the deficiency takes root, you will also notice stunted growth accompanied by the leaves cracking, shredding , and eventually falling off.

Because of manganese's role in photosynthesis and nitrogen assimilation it is very much an important part of a healthy plant's diet.

When new leaves begin turning yellow and show small, brown colored malignant spots in the center of the leaf, this is a sign of manganese deficiency.

Leaves start to disintegrate

Manganese deficiency will cause the veins of the new foliage to turn yellow.

causes yellowing between the veins of new foliage. In extreme cases new palm fronds emerge withered and dead. This is referred to as frizzletop, and commonly occurs on alkaline soils.

Some leaves that have yellowing between the veins will also have brown speckles on damaged leaves that can spread and destroy the whole leaf. Another thing – the leaves could fragment and disintegrate.

Manganese deficiency will stop the growth of your plant. It starts to become yellow at the bottom of the leaf, then spread more noticeably, getting closer to the tips.

How to Treat Manganese Deficiency

Luckily, once you have identified that your cannabis plant is suffering from a manganese deficiency there are some simple measures you can take. However, before you start supplementing, rule out pH as a cause for your deficiency first by carrying out a pH test and adjusting it if necessary. 

Foliar feeding

This is one of the effective ways of correcting a manganese deficiency. Foliar feeding basically means spraying a fertilizer straight onto your cannabis plants’ leaves. This provides the nutrients the plant needs directly through the foliage as opposed to the roots. This process has been proved both anecdotally and scientifically and many growers use it to solve their nutrient deficiencies.  Foliar feeding is both easy to carry out and very effective and if your cannabis plant is experiencing a shortage of manganese this should correct it quite speedily. You should however ensure that the foliar contains manganese and that it is diluted correctly to ensure the best results. 

Though often contested, regular spraying with a foliar also encourages the stomata of your cannabis plant to remain open as well as clean. Alterations in the water content around other secondary cells and the guard force the opening and closing of the stomata as a basic response to the changes in the water status.

Foliar feeding not only corrects deficiencies such as cannabis manganese deficiencies, it can also be incredibly beneficial to your weed plants. Regular spraying or misting with a light nutrient mixture can make a big difference.

Nutrient booster

Another method of fixing a marijuana manganese deficiency is introducing cannabis friendly nutrients which include manganese in the recommended amounts. However, the best way to apply this is to first flush out your media with clean pH’ed water which will also remove any extra iron or other nutrient salts which might be affecting the uptake of manganese. 

This method will ensure that your cannabis plant has the proper pH to encourage the uptake of manganese as well as introduce fresh nutrients containing manganese.

When adjusting your pH, avoid pH ranges that are higher as manganese deficiencies most often occur here. 

In soil, the best Ph for manganese absorption is by the roots is in the  6.0 – 7.0 pH range (though it is often recommended to keep the pH slightly lower in the ranges of 6.0 – 6.5, especially if you suspect your cannabis plants have a manganese deficiency)

In hydro, the best pH range for the roots to absorb manganese are the 5.5 – 6.0 pH range (the most recommended range for hydro is between 5.5 – 6.5, though manganese specifically tends to get best absorbed below 6.0)

Please note: Once you have treated the manganese deficiency, the symptoms such as yellowing leaves and brown spots will stop spreading. To ensure that your treatment method is effective, watch out for the new growth. 

However, if your cannabis plant experienced this deficiency during bloom, pruning away the affected areas may be a good idea as leaving necrotic growth on your cannabis plant may pose a huge risk of disease and pathogens. When pruning, ensure that it’s done in stages to avoid stressing the plant. 

Can you Mistake Manganese Deficiency for Other Deficiencies? 

A manganese deficiency can be confused for other deficiencies. The most often deficiency confused with the manganese deficiency is the iron deficiency. This is because they most often occur together as they are affected by the same conditions such as incorrect pH. Another similarity between these two deficiencies is that they both start from new growth and progress to older growth. Most of the time, the measures used to fix one of these deficiencies will resolve the other.

Calcium deficiencies are similar to manganese deficiencies as they also exhibit spotting on the leaves and the stunting of growth of the cannabis plant. However, calcium deficiencies can lead to more severe problems when left unchecked.

Another nutrient deficiency that gets confused with the manganese deficiency is the magnesium deficiency. Manganese and Magnesium deficiencies are usually confused because of both the similarities in their names as well as the properties of the deficiencies. Manganese deficiency symptoms in plants are quite similar to those of magnesium as they are both involved in photosynthesis. They both manifest in yellowing of leaves with interveinal chlorosis. However, manganese is more immobile in the cannabis plant than magnesium. This affects the way the deficiency [resents, with a manganese deficiency starting in the younger leaves and a magnesium deficiency affecting the older growth first. 

Keeping Your Cannabis Plants Free of Manganese Deficiency

The importance of manganese to your cannabis plant is great and highly impactful. Always ensure that you look out for this deficiency, especially if you are dealing with iron or zinc deficiencies. While manganese deficiencies are more likely to occur due to lock-out or improper absorption than a proper lack, the effect on your cannabis plants are the same. This is a deficiency that is particularly easy to miss or misdiagnose, so we hope you have learnt what to look out for and that you can catch it at the onset. 

Always ensure that your cannabis plants are well supplemented and that they have the correct PH to keep deficiencies at bay and ensure that you have the best harvest possible! 

A manganese deficiency is however easy to resolve and deal with and once it has been identified and treated. 

Happy growing!

Manganese Deficiency in Cannabis Q&A

What is manganese deficiency?

Manganese is a vital micronutrient that is important for creating chlorophyll, disintegrating enzymes, and an important part of the process of photosynthesis. It also plays a part in enabling nitrates to be used in the making of proteins, which is very important in cannabis plants. A manganese deficiency is a situation where manganese is either unavailable, or when it cannot be absorbed by the plant due to factors such as incorrect pH and nutrient lockout caused by other factors. When a manganese deficiency occurs, the processes it supports such as the manufacture of chlorophyll get affected and you might notice changes in the cannabis plant and general degradation.

It is however important to note that manganese deficiencies are infrequent and usually caused by other factors such as iron and zinc, and pH as we have mentioned. 

How do you solve manganese deficiency?

Once you have established that your marijuana plant is suffering from a manganese deficiency, you can do a few things to ensure that the problem is fixed.  To correct the manganese deficiency, the first step is identifying the source. Make sure the nutrition your cannabis plant accesses has at least the small manganese amounts needed by your cannabis plant. Also, carry out a pH test off your media run-off to ensure that the Ph is between 5.5 and 6.5. In addition, measure your solutions Ph. If you find that the pH of your media is off, you can flush the media using the correct pH, and then ensuring you introduce back properly balanced nutrients. 

If the pH is okay but your plant is still suffering from a manganese deficiency, a foliar feed fertilizer that contains manganese can be used to alleviate the issue. This can be added directly to the cannabis plant's soil. A good source of foliar is manganese sulfate which is readily available in most garden centers and which would work well in correcting a cannabis manganese deficiency. To avoid nutrient burn, ensure that any chemical nutrient you purchase is diluted to half strength.


Lydia K. (Bsc. RN) is a cannabis writer, which, considering where you’re reading this, makes perfect sense. Currently, she is a regular writer for Mace Media. In the past, she has written for MyBud, RX Leaf & Dine Magazine (Canada), CBDShopy (UK) and Cannavalate & Pharmadiol (Australia). She is best known for writing epic news articles and medical pieces. Occasionally, she deviates from news and science and creates humorous articles. And boy doesn't she love that! She equally enjoys ice cream, as should all right-thinking people.