Molybdenum: What Does It Do For Cannabis Plants?

Cultivating cannabis is often compared to a balancing act, between science and art. It's a process that requires attention to detail. You will be rewarded if you provide the plant with all essential nutrients and the right conditions to grow. Just like we humans need food for energy, plants depend on these nutrients to carry out various processes. 

So, while growing cannabis plants, we try to learn as much as we can about all kinds of common problems that our plants may face. That’s what every grower must do, and it will help you become a better grower. But what about the uncommon problems that your cannabis plant may face? 

These problems are rare and most growers may never experience them, but who’s to say you won’t? Molybdenum deficiency is one of them. This is a rare nutrient deficiency that can wreak havoc on your cannabis plant. It's just a micronutrient, but it does have some roles to play. 

Lack of molybdenum can hamper your plant’s growth, but it’s difficult to identify. Fortunately, though, fixing it is fairly straightforward. Want to know more? Learn everything you need to know about molybdenum deficiency in this article. 

What is Molybdenum and Why is it Important?

Molybdenum, a transition metal, plays a significant role in plant biology and nutrient absorption. Known for its silvery-white color, it belongs to the group of micronutrients — the very elements plants need in small quantities to grow and develop satisfactorily. Molybdenum has unique chemical properties where it combines and forms compounds with other elements and also influences several biochemical processes that are crucial for plants. 

Molybdenum functions as a cofactor for many enzymes in biological systems where it acts as a catalyst in reactions responsible for driving plant metabolism. In particular, it contributes to enzyme systems that are necessary for the uptake of nutrients and metabolism. Molybdenum acts as a cofactor for enzymes such as nitrate reductase and nitrogenase that play crucial roles in converting soil nitrogen into forms the plants can utilize.

For instance, nitrate reductase helps to convert nitrate into nitrite — a step that helps the plants use nitrogen effectively for growth. On the other hand, nitrogenase helps with nitrogen fixation which helps the plants use atmospheric nitrogen that is otherwise not accessible. 

The importance of molybdenum doesn’t end there — it extends beyond that, as it also helps the plant remain healthy. It’s not a regular micronutrient that participates in enzymatic reactions; instead, it plays a central role in shaping the plant's overall performance.

Molybdenum helps increase crop yield in plants like mustard. A lack of this nutrient can reduce yields in cannabis, so it makes sense that it plays a vital role in increasing the yields of cannabis plants. However, there are no particular studies done on cannabis alone, meaning we should take this information with a grain of salt. 

Molybdenum also ensures that the enzymes involved in metabolizing nitrogen function properly.  Although indirectly, it does influence the synthesis of amino acids, proteins, and other essential compounds that contribute to plant growth. 

What is Molybdenum Deficiency in Cannabis Plants?

The key to growing stunning cannabis plants lies in lies in providing the plant with the right conditions and essential nutrients. These nutrients are like the building blocks that contribute to the processes for optimal plant development, so if you take care and give everything the plant wants, it will deliver. Among these nutrients, molybdenum stands out as a micronutrient that significantly impacts the overall health and vitality of cannabis plants.

For professional cannabis growers, precision is the name of the game where each nutrient plays a role in shaping the plant's journey from seed to harvest. Molybdenum, although required in trace amounts, is a micronutrient that should not be underestimated. You may not have heard much about it, but it acts as a catalyst facilitating biochemical reactions within the plant. 

This micronutrient is used by cannabis for two crucial enzyme systems that are responsible for converting nitrate to ammonium. Further, this nutrient is also crucial for the plant’s seeds and roots. 

But sometimes, the plant may not get enough molybdenum while growing — this is rare but it can still happen. This problem is called molybdenum deficiency, which can significantly impact your plant’s growth. But before we get into identifying this problem, let’s learn about what causes molybdenum deficiency. 

In most cases, molybdenum deficiency is caused by pH issues, like most other nutrient deficiencies. In this case, if your plant’s pH is too low or acidic, the roots can fail to absorb molybdenum from the soil. Improper pH can cause nutrient lockout in the roots, and this is one of them. There may be a lot of molybdenum in the soil, but the roots will still fail to absorb it properly. 

Molybdenum deficiency can occur if the nutrient is not present in the soil in the first place, but that’s extremely rare. Your plant requires this nutrient in trace quantities and most high-quality soil and fertilizers contain this mineral by default. 

So, if you are growing cannabis, it is crucial to keep an eye on the pH of the growing medium — this will help you avoid most nutrient deficiencies, including molybdenum deficiency. 

How to Identify Molybdenum Deficiency in Cannabis?

Image Credit - horn1 

This is where things get tricky with molybdenum deficiency — it is one of the most difficult deficiencies to diagnose and even experienced growers can break their heads, metaphorically, trying to identify this problem accurately. 

But if you are patient and take the right approach, you can identify molybdenum deficiency quickly. It may still take some trial and error, so being patient and having an open mind is crucial to identifying molybdenum deficiency in cannabis. 

Remember, you must never ignore this deficiency, no matter how healthy your plant looks because it’s only a matter of time before your plant starts showing its age way before it’s due. Here are the major symptoms of molybdenum deficiency in cannabis plants. 

1. Leaves

• Leaf Chlorosis

Although leaf chlorosis could be anything from a pH imbalance to another nutrient deficiency, it’s one of the indicators of molybdenum deficiency. First, you’ll see that the vibrant green color of cannabis leaves fades into a yellow hue due to an interruption in chlorophyll production that affects the plant's ability to efficiently photosynthesize. The deficiency directly impacts reductase, which is an enzyme in nitrogen metabolism that leads to chlorophyll breakdown resulting in the distinct yellowing displayed in affected leaves. 

Typically, leaf chlorosis in a molybdenum deficiency starts at the edges of the leaves and between the veins resulting in a marbled look. Gradually, the yellowing spreads inward and the space between the veins becomes prominently yellow over time. Although you might think it’s a nitrogen deficiency at first, it becomes obvious because it affects specific parts or edges of the leaves. 

As the problem progresses, the leaves may also turn distinctly red, orange, or pink, especially at the edges, which will eventually start moving inward — this is a distinct symptom of molybdenum deficiency and must be noted to avoid confusion. Do note that, in some cases, the color may develop in the center, too. 

• Abnormal leaf growth

Molybdenum deficiency can lead to abnormal leaf development where the leaves become distorted. You may see the leaves getting twisted or cupped, which occurs when the normal physiological processes regulated by molybdenum are disrupted. Since molybdenum plays a critical role in enzyme systems that regulate plant growth, a deficiency can lead to misshapen leaves, which affects the structure of the plant.

Apart from distorted leaves, the leaves' structure can also be affected. As the deficiency progresses affected leaves may start curling. This abnormality clearly indicates that even though molybdenum is needed in minute amounts, it plays a role in maintaining the strength and integrity of plant tissues as well as overall leaf structure. Sometimes, the leaves may become speckled or mottled if they suffer from a lack of molybdenum. 

• Necrosis

If you don’t correct the problem in time, the deficiency worsens and can lead to necrosis, where the leaves turn brown and die eventually. As molybdenum helps in preserving both the functional and structural integrity of plant cells, scarcity can disrupt the enzymatic processes and lead to necrosis. In addition, the leaves can become dry and brittle. 

These are secondary symptoms, so always take these symptoms into account with the primary symptom of leaves turning pink.

2. Unhealthy Plant Growth

Once the deficiency progresses, the leaves will turn colors, which will impact their function. This can lead to all kinds of energy-related problems within the plant, resulting in improper plant growth. Over time, this can lead to loss of vigor, slow growth, or subpar yields. 

3. Roots

The next symptom of molybdenum deficiency shows up in the roots — the pH of the rhizosphere will be too low. While this is not exactly a symptom that shows up on the plant itself, it is a reliable indication that your plant may be suffering from molybdenum deficiency, especially if the leaves are turning pink, red, or yellow.

Remember, molybdenum deficiency is rare, but it can still occur. And when that happens, it can be difficult to diagnose. So, it is important to also know the symptoms of other common nutrient deficiencies and you can use deductive reasoning to eliminate other deficiencies and narrow in on molybdenum deficiency. 

How to Treat Molybdenum Deficiency in Cannabis Plants?

As difficult as it may be to diagnose molybdenum deficiency, it is actually quite easy to fix molybdenum deficiency in cannabis plants. Almost always, fixing the pH is the cure for this problem. 

So, the first step to fixing molybdenum deficiency in cannabis plants is to flush the growing medium with pure water that has a pH of 6.0. Flushing will remove all the excess salts and nutrients that may be causing a nutrient lockout within the soil. Think of flushing as a reset button for the growing medium.

Once the growing medium is flushed, the next step is to check and rebalance the pH. For this, you will need a pH meter and possibly a pH correction solution. Start by checking the pH of the nutrient solution followed by the same of the runoff water — both readings should be identical. 

If the pH is not above 5.5, under which molybdenum deficiency occurs, you need to use a pH-correcting solution to fix the problem. Ideally, the pH should be between 5.8 to 6.2 in most cases. Remember, higher pH can also be an issue for cannabis plants, so don’t overcorrect. 

High pH levels could prevent the plants from absorbing sufficient amounts of molybdenum even if it is present in the soil, so you must adjust the pH whenever necessary. Also, remember that excessive amounts of other micronutrients typically cause nutrient lockouts. In this case, copper or iron can limit molybdenum absorption. 

Furthermore, the soil composition and structure also impact molybdenum availability. Sandy soils, for example, may have low levels of molybdenum, so you’ll have to use micronutrients regularly if you’re using them to grow cannabis plants. In addition, compacted or waterlogged soils can restrict root access to molybdenum. Therefore, you must not overwater and use soil that’s well-aerated. 

Finally, you may have to take an unpleasant approach to treating molybdenum deficiency in cannabis plants: pruning. If the situation has gotten severe, your plant may have some permanent damage, and now it’s time to remove it by pruning. 

So, cut off the leaves that have completely lost their color, turned pink, or curled up. These leaves may not function as well as healthier leaves but may still consume energy from the plant, which is not ideal since that energy can be used by other healthier parts of the plant. 

How to Prevent Molybdenum Deficiency in Cannabis Plants?

As with most nutrient deficiencies your cannabis plant may face, defense is the best offense. And just because molybdenum deficiency is rare doesn’t mean you overlook the prevention. Here are a few tips to help you avoid molybdenum deficiency in the first place. 

The first step in preventing molybdenum deficiency is to keep an eye on the pH of the root zone. It should always be in the ideal spot of being slightly acidic, not too much. It is advisable that you invest in a high-quality pH pen and regularly test the pH of the nutrient solution and the runoff water — if the runoff pH is different, the growing medium may have salt buildup. 

The pH becomes especially important if you are growing your cannabis plant hydroponically. This system of cultivation is often unforgiving and precision matters the most. So, if the pH drops below 5.5, expect your plant to suffer from molybdenum deficiency. 

Additionally, you should be mindful while feeding your cannabis plant. Always ensure you give them high-quality fertilizers that, one, contain all the micronutrients including molybdenum, and two, don’t contain high levels of some nutrients that may cause nutrient lockout or pH imbalance. 

Ideally, you should stick to high-quality organic grow mixes or fertilizers that are designed for cannabis plants. These products contain all the necessary nutrients and minerals required for your cannabis plant to grow well. 

The third step is to maintain an ideal growing environment, including temperature, humidity, air quality, etc. These things may not directly impact molybdenum absorption in your cannabis plant, but they can create a cascading effect that eventually leads to molybdenum and other forms of nutrient deficiencies. 

Summary: Molybdenum: What Does It Do For Cannabis Plants?

Your cannabis plant does not need a lot of molybdenum, it’s a micronutrient and is only required in small quantities. Nonetheless, it is still crucial for your plant’s enzymes, leaves, and roots. Lack of this nutrient means your plant may not grow well, produce enough energy, and eventually develop a subpar yield. 

Unfortunately, molybdenum deficiency is hard to diagnose, but always look out for pink leaves along with the low pH of the growing medium. And as mentioned earlier, use the process of deduction to make sure it’s not another nutrient deficiency. 

If you are sure it is molybdenum deficiency, fix the pH of the growing medium and prune the affected leaves and you should be good to go. Keep an eye on the pH and use high-quality fertilizers to prevent this problem in the future. 

To know more about such uncommon problems your cannabis plant may face, stay tuned to our blog. We post regular grow guides that help you become a better grower.