Updated: Dec 15, 2020
On your journey as a cannabis grower, you can run into a number of problems, but with a bit of research and guidance, you can tackle those problems easily. One of the possible issues that you can run into is manganese deficiency in your cannabis plants. Although the occurrence of this problem is rare or uncommon, it can be fixed very easily. This guide will not only help you identify the symptoms of manganese deficiency in your plants but will also provide you with adequate treatment methods and prevention tips.
How Manganese Is Used By Cannabis Plants
Manganese is a micro and immobile nutrient that is essential for numerous functions in cannabis plants - including photosynthesis. As a matter of fact, manganese (Mn) is required in the very first step of photosynthesis known as water-splitting reaction. It is also required for other basic and important functions like respiration and assimilation of nitrogen. Manganese is needed in chlorophyll composition and enzyme catalysis. It is also essential for the formation of trichomes which helps the plant deter pests. Manganese keeps the roots strong and protects them against various pathogens. A plant’s root system is essentially its life and that is why manganese is of great importance. Now that you know that manganese is required for your cannabis plants to be healthy and thrive, the next step is to determine the signs that indicate manganese deficiency in cannabis plants.
Symptoms of Manganese Deficiency in Cannabis Plants
Manganese deficiency is not difficult to detect as the symptoms are distinguishable to a good extent. The symptoms start affecting the new growth first as this problem is relatively immobile. If you observe your plants regularly, the top of the canopy is where you will see the signs. But if not treated quickly, you will start seeing the signs in older leaves too.
To avoid misdiagnosing the problem, check for the following symptoms on your cannabis plants:
New leaves start turning yellow between the veins; this is called interveinal chlorosis.
The edges may turn dark green so you will see yellowing between veins transitioning to a darker green shade towards the edges.
One of the key indicators is necrotic or dead, brown spots that start appearing on the leaves - mostly in the center. These brown spots can spread to the entire leaf and destroy it completely.
Random spotting on the leaves is another noticeable symptom of manganese deficiency in cannabis plants.
You will see it affect overall plant growth; manganese deficiency can potentially stunt a cannabis plant’s growth.
Eventually, these symptoms will move towards older leaves from new growth - this malady moves from top to bottom.
Some growers mix manganese deficiency with iron deficiency but there are a few signs that can help avoid a misdiagnosis. One of the differences in symptoms is that with manganese deficiency, the yellowing part becomes brown or tan with time whereas when plants are deficient in iron, the yellowing leaves tend to become white or grayish. This is how you can distinguish between the two problems that are often tied together.
Now that you know the telltale signs of manganese deficiency in cannabis plants, you can easily identify it if it affects your cannabis plants. Since it can stunt plant growth and destroy the leaves, it is important to treat the deficiency as soon as possible after the diagnosis.
Causes of Manganese Deficiency in Cannabis Plants
Knowing the causes of manganese deficiency will help you become a proactive grower and you can take preventative measures to avoid the problem in the first place. Manganese deficiency usually occurs when a plant cannot absorb or uptake manganese. The correct term for this hurdle is manganese lockout. This happens when the pH levels of the medium are too high or inadequate. The required pH levels for optimal absorption of manganese vary depending on the medium that the plant is being grown in.
In a soil medium, manganese is best absorbed by the plant when pH levels are between 6.0 to 6.5
In a soilless medium, manganese is best absorbed by the plant when pH levels are between 5.5 and 5.8
Other causes of manganese deficiency are over-watering the plant or not providing a proper system for drainage.
Treatment of Manganese Deficiency in Cannabis Plants
Now that you are aware of the causes of manganese deficiency in cannabis plants, you are all equipped to treat it. Since the main cause of this deficiency is running into a lockout due to high pH levels, the best solution is to fix the pH level. It is very important that the pH level is fixed before providing the plant with any supplements - since that can make the symptoms worse.
To bring the pH to correct level, flush your root system with pH-balanced water. Since excessive or overabundance of iron can cause manganese deficiency, flushing the system will help get rid of the iron buildup and salts while getting the pH back to the right level. After flushing, you can provide micronutrient supplements to the plant that contain manganese. You can use manganese chelates too for this purpose. Greensand may also do the trick, but slow absorption impedes this one. Besides that, prune any leaves with necrotic patches as they will not recover with the treatment.
By taking these steps, you will see major changes within one week, but the affected growth will not recover.
Preventing Manganese Deficiency in Cannabis Plants
Prevention is certainly better than cure. To prevent manganese deficiency, keep an eye on the pH level of the growing medium. You can purchase a pH meter to be extra careful. Make sure that your plant has proper drainage and water is not collecting in the grow pot. Do not overwater your plant and provide your plant with micro-nutrient supplements when needed.
With these tips and preventative measures, you now know how to correct and avoid manganese deficiency in cannabis plants.
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