Understanding The Importance Of Zinc In Growing Cannabis: Roles, Deficiency, And More

When growing cannabis, we focus on many nutrients, especially macronutrients like nitrogen, phosphorus, and potassium. But one of the common nutrients that are easy to overlook is zinc. Zinc nutrient is crucial for your cannabis plant, but since it doesn’t require it in large quantities, it can sometimes make us think it’s not as important as the rest. 

Truth be told, zinc is crucial for your plant’s energy production, sustenance, and yield. Without zinc, your plant may fail to create enough energy or grow tall, and in severe cases, zinc deficiency can even kill your plant.

So, what is zinc deficiency and how do you fix that in your cannabis plant? Here’s everything you need to know about zinc deficiency. 

Why is Zinc Important for Cannabis Plants?

The significance of micronutrients in growing healthy cannabis plants can’t be overstated as they play a major role in physiological and biochemical processes that are necessary for the health and development of plants. While plants require macronutrients like nitrogen, phosphorus, and potassium in large quantities, micronutrients are equally important. Although the plants require only small amounts of micronutrients, they are very important for the plants to grow, reproduce, and produce good yields, including cannabis. 

Typically, plants absorb zinc in its divalent cation form (Zn2+). Zinc plays a key role in plant physiology as it activates enzymes and acts as a cofactor in metabolic pathways. Although zinc deficiency is not very common in soils, factors like soil pH, composition, and environmental conditions can affect its availability. 

Zinc may not be a macronutrient for your cannabis plant but it’s still a crucial micronutrient for the plant. With magnesium and manganese, zinc plays a crucial role in enzyme production and function in the plant. Additionally, this nutrient works with other nutrients for the production and sustenance of chlorophyll in the leaves, and by extension, this makes zinc crucial for the plant’s survival. 

Zinc also performs various other functions in the plant, including the production of carbohydrates, helping convert starch to sugar, and even building the plant’s resistance against low temperatures. Lastly, zinc is a crucial component of auxins that help the stem grow tall. 

As a result, zinc is vital for your plant’s health and if it does not get enough zinc, especially during its growth stage, it may suffer from various issues, including loss of chlorophyll, slow or stunted growth, weakness, etc. This is why it’s crucial to prevent zinc deficiency in your plant.

Here’s a quick overview of the importance of zinc:

1. Enzyme Activation

Zinc serves as an activator for enzymes involved in metabolic processes. These enzymes are responsible for synthesizing DNA, RNA, proteins, and other essential molecules. Zinc’s involvement in activities is vital for the functioning of plant cells.

2. Photosynthesis

Photosynthesis is a process where plants convert light into chemical energy like glucose. Chlorophyll, the pigment found in plants that is responsible for their color, absorbs sunlight, captures energy, and initiates chemical reactions that ultimately produce sugars and oxygen.

Zinc aids in the creation and stability of these chlorophyll molecules. It also helps with absorbing light during photosynthesis. The process of synthesizing chlorophyll is pretty complex and involves several steps. Zinc serves as a cofactor for various enzymes that participate in these steps and also helps to assemble chlorophyll molecules. Needless to say, maintaining sufficient levels of zinc ensures a balanced synthesis of chlorophyll — a critical factor contributing to overall plant performance during photosynthesis.

Conversely, a lack of zinc compromises the synthesis of chlorophyll, resulting in a decreased ability for plants to capture light energy effectively. Typically, you’ll see this disruption as chlorosis, where leaves turn yellow as they don’t have enough chlorophyll. Reduced chlorophyll makes it harder for the plant to capture sunlight efficiently. Ultimately this can affect the plant's growth, yield, and overall health.

3. Nutrient Transportation

Plants grow well when they can absorb essential nutrients efficiently. Zinc plays an important part in this process by influencing how various nutrients are taken up and transported within the plant.

For example, zinc helps the plant absorb phosphorus by affecting cell membrane permeability. In fact, if you add high amounts of phosphorus fertilizers, adequate zinc is required to prevent imbalances. 

Zinc also supports a healthy root structure that’s important to absorb nutrients. It produces auxins, which are nothing but hormones for root elongation and branching. A root system that’s well developed enhances the plant's ability to search the soil for nutrients and water, strengthening its capacity to absorb nutrients.

Once the plants absorb the nutrients, they need to be transported to parts of the plant, including zinc. As a mobile nutrient, zinc moves within various parts of the plant and supports physiological processes. This includes its contribution to enzyme and protein synthesis and also maintains the structural integrity in different plant tissues.

Sufficient zinc levels in the plant enhance its efficiency in the uptake of nutrients and carry out essential cellular processes. This in turn makes it easier for the plant to develop leaves, reproduce, and produce seeds. 

4. Stress Response and Disease Resistance

Zinc enables plants to respond to various environmental stresses by serving as a cofactor to enzymes that are involved in signaling pathways responding to stress and also help with the plant’s defense mechanisms. When plants face challenges like drought, salinity, or extreme temperatures, zinc-dependent enzymes minimize the impact of these challenges. It activates enzymes that enhance the plant’s defense against fighting oxidative stress. 

Zinc also helps in synthesizing plant hormones that are crucial for stress responses, controlling processes such as seed dormancy, and defense mechanisms against herbivores and pathogens. Thus, plants with sufficient levels of zinc can cope with stress.

What’s more, zinc improves disease resistance in cannabis plants by aiding in the production of compounds that enhance the plant’s immune system. These compounds act as barriers against pathogens and contribute to overall disease resistance.

What Causes Zinc Deficiency in Cannabis Plants?

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Preventing zinc deficiency is the default option, but sometimes, your plant can still experience zinc deficiency even if you try your best to care for the plant. And while you may think it may be due to a lack of zinc in the soil, this may not always be the case. Zinc deficiency can occur due to a combination of various factors including nutrient interactions, pH of the soil, condition of the soil or growing medium, and more. Regardless of the reason, identifying the problem on time will save you from lots of problems. 

Zinc deficiency can be caused due to various reasons, such as the following. 

1. High pH of the Growing Medium 

One of the most common causes of zinc deficiency in cannabis plants is the growing medium being too alkaline. When the pH is too high in the growing medium, the alkaline environment can make it difficult for the roots to absorb nutrients — remember, cannabis likes slightly acidic mediums. 

The soil serves as the primary source for plants to absorb many nutrients including zinc, and cannabis is no exception. However, its availability to plants is influenced by various factors such as soil pH, competing ions, and organic matter. Therefore, you have to maintain a proper pH range and address any imbalances in the soil to ensure the uptake of zinc. While zinc will be available to the plants at a pH ranging between 6.0 to 7.0 in soil, it should be between 5.5 and 6.5 in hydroponic systems. 

2. Excess Watering 

It’s natural to think that more water is better for cannabis since it is a thirsty little plant, but you’d be wrong. Overwatering cannabis can affect your plant in two ways. One, overwatering can wash away the nutrients, including zinc, from the soil, leaving nothing for your plant to absorb. 

On the other hand, overwatering can lead to stagnant water buildup in the growing medium, which will not only choke the roots and inhibit them from absorbing nutrients but can also lead to root rot, which can further affect the roots’ nutrient absorption rates. 

3. Stress

Stress is not good for anyone — not you, not your pet, and not your cannabis plant. When a cannabis plant experiences stress, it can temporarily fail to absorb zinc along with a few other nutrients. This issue usually settles on its own, but it’s important to figure out what is causing stress; it could be anything from extreme temperature to irregular light cycles. 

4. Fungi or Pests

The health of the roots is directly related to zinc absorption in cannabis plants, and if the roots are compromised in any way, the plant may suffer from zinc deficiency. This usually happens due to fungus or pests like mites, inchworms, or fungus gnats, which can cause a lot of root damage. 

5. Organic Fertilizers 

Yes, organic cultivation is always better than chemical-based ones, but there’s a downside to it — organically grown cannabis plants are vulnerable to pH fluctuations. Organic fertilizers can quickly offset the pH of the soil, causing zinc deficiency. This is not common, but it can still occur in some cases where organic fertilizers aren’t used correctly. 

Along similar lines, low-quality fertilizers may also cause zinc deficiency in cannabis plants. High-quality fertilizers contain nutrients that can be easily absorbed by the cannabis plant, but poor-quality ones may not. Some poor-quality fertilizers don’t even contain some micronutrients!

6. Too Much Phosphorus in the Medium 

A common issue that many hydroponic growers face is a sudden burst of phosphorus in the growing medium, which can trigger zinc deficiency in cannabis plants. What happens is, when a hydroponic system is out of nitric acid, it switches to phosphoric acid to regulate the pH, and this can push the plant into a nutrient lockout. 

7. Texture and Soil Composition 

There are various types of soil available to grow cannabis plants. While some of them are rich in organic matter and texture, sandy soils typically contain less zinc compared to other types of soil. This is why your plant may experience a deficiency in zinc if you choose to grow them in sandy soils. You can improve the composition of the soil by adding organic matter such as compost to make more zinc available to the plants. 

8. Excessive Iron or Copper

When there are high levels of iron or copper in the soil, it can hinder zinc absorption as they can compete with it for absorption, thereby leading to a deficiency. Therefore, it is important to use soil or add fertilizers containing a balanced amount of nutrients. 

9. Root Damage or Compaction

Unfavorable soil conditions where the soil gets compacted and makes it difficult for the roots to spread will be problematic. Also, the plant can struggle if there’s less aeration as that hinders root development as well. At this point, the plants will find it hard to absorb not just zinc but many other nutrients too, leading to a combination of deficiencies. Thus, try and use soil that has a good texture to support root growth. 

10. Water Quality

If you use hard water containing high levels of calcium and magnesium, it can interfere with the absorption of zinc. Thus, you should either check the water you’re using beforehand using a TDS meter or use soft water. 

How to Identify Zinc Deficiency in Cannabis Plants?

One of the signs of zinc deficiency in cannabis is chlorosis where you’ll see yellowing leaves. Now, chlorosis occurs due to a range of other deficiencies including nitrogen. So, how do you differentiate between zinc and other deficiencies? Well, what sets zinc deficiency apart is the pattern of yellowing, where the spaces between leaf veins turn yellow while the veins themselves remain green. This creates a mosaic type of appearance on affected leaves.

1. Necrosis and Browning at Leaf Edges

Once there’s a zinc deficiency and you fail to correct it on time, it progresses up to a point where the edges of leaves may display necrosis or browning. Compared to other signs, this is more noticeable, at the tips and margins of leaves. If you touch the leaves, you’ll see that the necrotic areas also feel crisp, which is a sign that the plant needs your urgent intervention. 

2. Leaf Abnormalities and Reduced Size

Zinc deficiency can also cause the leaves to grow small. If you’ve grown quite a few cannabis plants, you’ll have an idea about healthy leaf size, but zinc deficiency can cause stunted leaf growth and prevent it from growing to its full size. In addition, the leaves may seem narrow or even distorted. 

3. Delayed Flowering and Reduced Bud Formation

Zinc deficiency can impact the development of plants where the plants can delay their flowering. You’ll also probably notice that the plants don’t produce as many buds as they should, which is common when the growth is stunted. 

4. Impaired Growth and Shorter Gaps Between Stems

Zinc deficiency can also affect the internodal space. Although this is a welcome sign for many growers who love to have bushy and compact indica plants, it’s not a good thing to have especially when the plants grow small due to a zinc deficiency. This is because the plants will eventually produce little yields compared to naturally compact plants. 

5. Reduced Root Development

Insufficient zinc can affect the roots negatively. The overall mass of the roots is reduced, and when the roots have a problem, the entire plant will suffer. Also, a compromised root structure limits the plant's ability to absorb water and nutrients from the soil, so you’ll have too many problems before you know it. 

If you notice these symptoms on your cannabis plant, you can be sure your plant is suffering from zinc deficiency. 

In summary, this is what happens when your plant experiences a zinc deficiency:

1. Interveinal chlorosis, i.e., the interstices turning slightly yellow 
2. The leaf tips start turning brown and curling while the chlorosis spreads 
3. Chlorosis will take over the entire leaves and new growth will have stopped entirely

Apart from this progression, you may also notice the following symptoms on your cannabis plant:

• The part between the veins turning yellow on the leaves 
• The leaves may appear distorted
• The plant stops growing tall 
• Flower production stops and some buds may even die 
• New growth may turn white, yellow, or bronze 
• Narrow-leaf growth 
• The leaves may develop waxy margins 
• Yellowing of leaves and areas between veins

How to Treat Zinc Deficiency in Cannabis Plants?

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Fortunately, treating zinc deficiency is fairly easy. All you need to do is take a few steps and the problem should be fixed soon enough. Follow these steps to treat zinc deficiency. 

Preventing Zinc Deficiency in Cannabis

1. Proper Soil Preparation

To enhance the structure of the soil, start by improving the drainage or aeration so that the roots have ample space to spread without any issues. As mentioned earlier, organic matter can increase the availability of zinc, so add some compost or worm castings that not only add zinc but also condition the soil. The added benefit is that it will also increase the microbial activity in the soil, making it a win-win situation. 

Apart from natural matter like compost and worm castings, you can also add fertilizers enriched with a balanced amount of micronutrients into the soil. It’s even better if the fertilizer releases micronutrients slowly into the soil as you can rest assured that the plants have a steady supply of nutrients. 

2. pH Management

The pH of the soil or any growing medium should always be a point of concern for you, especially when you're growing cannabis indoors. As mentioned already, try and maintain a pH ranging from 6.0 to 7.0 in soil and 5.5 to 6.5 in hydroponic mediums for better zinc uptake. Remember, excess alkalinity can reduce zinc solubility, so use appropriate amendments and soil conditioners to prevent this problem.

Ways To Treat Zinc Deficiency

1. Start by Adjusting the pH

In most nutrient deficiency cases, imbalanced pH is usually the culprit, and zinc deficiency is not an exception. So, start here to fix zinc deficiency in your cannabis plant. For this, you need a pH meter so you can check the pH of the soil. 

If the pH is beyond what’s recommended for your cannabis strain, you need to act quickly. First, you need to flush the growing medium to remove excess salt buildup that may be causing the pH to rise. Then, you can use a pH-down solution or aluminum sulfate to bring the pH down in the growing medium. 

Remember to always choose high-quality pH correction solutions and follow the manufacturer’s recommendations. You don’t want to fix one deficiency and end up with ten others. 

2. Flush the Growing Medium 

Even if the pH is alright, it is still a good idea to flush the growing medium regardless. Sometimes, salt buildup within the soil can cause nutrient lockouts, which can exhibit itself as zinc deficiency. 

Essentially, flushing the growing medium is running gallons of water through the growing medium until the nutrients have been flushed out — it’s like a reset for the growing medium. 

3. Add Zinc to the Soil 

If the above steps don’t fix zinc deficiency in your plant, you may not be giving your plant enough zinc in the first place. So, add more zinc to the nutrient supply via zinc-rich fertilizers. Always make sure you use high-quality fertilizers with all the micronutrients. 

Also, while doing so, don’t add too much fertilizer to the plant. You may want to give your plant a zinc boost, but it probably won’t go well. Instead, gradually increase the zinc supply to the plant. 

Foliar Spray

In the meantime, you can still apply foliar to your cannabis plant since plants absorb the nutrients quickly via the leaves. This is not a treatment, it’s a temporary solution to the problem. So, use zinc foliar spray to give your plant a zinc boost while you fix the underlying cause of the problem. 

In addition, as organic matter decomposes gradually in the soil, it tends to release zinc, adding to the various nutrients present already for efficient uptake. Thus, you can add some compost to the soil to increase zinc levels.

4. Check the Roots 

Lastly, you should check the roots. The roots of your cannabis plant should be healthy, not root-bound, or infected with pests or fungus. If the roots are clogged up due to anything else, you need to take the appropriate action to fix the issue. This would include solutions like moving your plant to a bigger container, washing the roots, changing the growing medium, etc. 

Summary: Understanding The Importance Of Zinc In Growing Cannabis: Roles, Deficiency, And More

As you can see, zinc is crucial for your plant’s growth and when your plant doesn’t get enough of it, it can show symptoms like yellowing leaves, curled leaves, or stunted growth. Do not take these symptoms lightly as zinc deficiency can eventually kill your plant.

So, if you notice the symptoms, start taking the correct action to fix the problem, including flushing the soil, correcting the pH, and adding more zinc to the nutrient supply. But what’s better than treating zinc deficiency is preventing it in the first place. 

You don’t need to take any special steps to prevent zinc deficiency. It’s fairly easy to prevent as long as you take general good care of your cannabis plant. So, your aim with your cannabis plant should be to make sure the roots are thriving with adequate nutrient supply and correct pH.

The best pH for hydroponic cannabis plants is between 5.5 to 6.5 and the same for soil-based cannabis plants is 6.0 to 7.0. And avoid overfeeding or overwatering your cannabis plant at all costs — that’s inviting trouble. 

Apart from all that, ensure your cannabis plant lives a stress-free life. The plant shouldn’t experience extreme temperature fluctuations, pests, fungal issues, or other environmental risks. If all is taken care of, your plant will avoid zinc deficiency easily.