The Importance of Micronutrients for Growing Cannabis: A Detailed Guide

When growing cannabis, new growers focus on all the major aspects of the plant’s requirements — lights, humidity, temperature, NPK nutrients, etc. But often, the littlest things can make the biggest difference. 

Micronutrients are a group of such little things that can significantly affect how your cannabis plant grows. Your plant doesn’t need a lot of them — only a drop of micronutrient to a gallon of macronutrient, metaphorically speaking — but when your plant does not get enough of them, it can lose vigor quickly.

But what are these micronutrients, why are they important, and what can happen if your plant experiences micronutrient problems? Learn about the micronutrients your cannabis plants need, common micronutrient deficiencies and toxicities, and how to fix them. 

Here’s everything you need to know about micronutrients for growing cannabis. 

Micronutrients for Cannabis

In gardening, you will come across two types of nutrients — macronutrients and micronutrients. The former refers to primary nutrients that your plant requires in the highest concentrations. There are three macronutrients, nitrogen, potassium, and phosphorus, collectively known as the NPK nutrients. 

On the other hand, micronutrients, also known as trace elements, are nutrients or minerals your plant needs in fewer amounts. To be precise, a trace nutrient refers to an element present in the soil at less than 1,000 ppm. 

Note: Trace elements and micronutrients don’t mean the same thing, but when it comes to cannabis cultivation, the terms are used interchangeably. 

But don’t let the term “micro” fool you. Even in minuscule quantities, these minerals are essential for healthy plant growth. These nutrients are just as important as macronutrients, and a lack of them can cause symptoms of deficiencies in your cannabis plant. 

If you use tap water for irrigating your cannabis plant, you don’t even have to worry about supplementing most of the micronutrients — tap water already contains most of them. But you will need to test your tap water with a TDS meter just to ensure they don’t exceed the requirements of the plants. 

Even rich outdoor soils contain most of the micronutrients naturally, so you don’t need to worry about your soil-based plant experiencing micronutrient deficiencies. However, if you are growing cannabis hydroponically or use filtered water, you can apply micronutrients to your plant as foliar spray or add them to the nutrient solution. 

Most Essential Micronutrients for Cannabis Plants

Your cannabis plant requires a long list of micronutrients, including some which are required by specific varieties of cannabis and some others that are entirely optional. While we can’t get into each and every micronutrient your plant requires, here are some of the most important micronutrients and how they help your plant grow. 

1. Boron 

Boron is one of the most important micronutrients for cannabis as it aids tissue growth — it influences cell wall development. 90% of the boron used by cannabis helps build carbohydrate molecules that build the cell walls. Boron also helps regulate your plant’s metabolism and absorption of water from the growing medium. 

2. Chlorine

Chlorine is another crucial element that your plant requires in trace quantities, but this nutrient plays a role in photosynthesis, disease resistance, and hydrolysis. Additionally, chlorine works with potassium in the stomata of the leaves. 

3. Copper

Your cannabis plant requires copper in minute quantities — between 0.05 to 0.5 ppm — but it still plays a major role. It is responsible for an enzyme activity that synthesizes lignin, and it is also required for photosynthesis, respiration, and carbohydrate and protein metabolism within the plant. Copper also plays a role in producing the rich flavor and color of the buds. 

4. Iron

Iron is a semi-mobile nutrient that plays a role in your plant’s photosynthesis processes and helps maintain its structure. Essentially, iron is used in the production of chlorophyll, and it is also a crucial element for various pigments and enzymes. 

5. Manganese

Manganese is primarily used for nitrogen assimilation in cannabis plants, but it also plays a role in the formation of proteins, seed germination, production of chlorophyll, and general plant growth. 

Since manganese is a crucial part of some of the most important functions of the cannabis plant, you need to ensure your cannabis plant gets enough of this. However, manganese deficiency is still rare, so not something every grower needs to worry about. 

6. Molybdenum

Molybdenum is a micronutrient that is used for the production of nitrogen-based proteins and it is also crucial for nitrogen assimilation. Another role that this mineral plays is that it allows the plant to synthesize amino acids like nitrite and ammonia. 

7. Nickel

Cannabis plants use nickel to metabolize urea, a source of nitrogen, and it also aids in the formation of enzymes that influence plant development. Nickel is also involved in various secondary metabolic processes in cannabis plants.

8. Zinc

Zinc is used in small doses but leads to major changes within the cannabis plant. This immobile nutrient is also an important element used in forming various proteins and enzymes, and it also aids internode elongation and the production of growth hormones. 

Secondary Macronutrients for Cannabis Plants

Apart from the NPK macronutrients, your plant also requires other secondary macronutrients that can be clubbed with the micronutrients mentioned above. The three secondary macronutrients are calcium, magnesium, and sulfur. Let’s take a look at these.

1. Calcium

Calcium is crucial for your plant’s structure; this immobile nutrient is present in the form of calcium pectate, which keeps the cell walls and membranes in place. Calcium also acts as an intracellular messenger for hormone regulation and enzyme activity.

2. Magnesium

Magnesium is a mobile nutrient that is the primary force behind photosynthesis. This element is the building block of chlorophyll, enabling the molecule to capture light for energy production. Magnesium is also important for protein synthesis, cell division, enzyme activation, and phosphate metabolism. 

3. Sulfur 

While your cannabis plant only requires this element in minor quantities, it is crucial for enzyme production and synthesis of vitamins, proteins, and amino acids. Without this semi-mobile element, your plant would struggle to perform its most basic functions. 

Recommended Amounts of Micronutrients for Cannabis Growth

Although these micronutrients are required in small quantities by the cannabis plant, a deficiency can cause many problems for your plant’s health. We will go into micronutrient deficiency in the following section, but let’s look at the recommended amounts of micronutrients needed for the cannabis plant.

Remember to adjust these numbers based on your plant’s growth stage, strain, and local growing conditions. These are just general guidelines but may not reflect the quantities required for your specific plant. 

Common Micronutrient Problems in Cannabis Plants

Even though your cannabis plants require micronutrients in trace amounts, they are still crucial for the plant’s growth. Even if one of the micronutrients is missing, your plant can experience various problems that can affect its growth, performance, and even yield. 

On the other hand, if these micronutrients are in excess, they can lead to various problems. This is because these micronutrients influence the performance of macronutrients within the cannabis plant.

So, to help you understand the problem better, here are some common micronutrient problems or deficiencies you may face while growing cannabis and how to fix them.

1. Zinc Deficiency or Toxicity

Zinc deficiency is one of the most common micronutrient deficiencies you may face while growing cannabis, and it can lead to various problems. As mentioned earlier, zinc is responsible for the creation of chlorophyll along with various hormones and auxins. 

And this mineral is absorbed via the roots in the form of Zn2+ (bivalent ion), but if the pH is too acidic, the roots fail to absorb zine properly. This can also happen due to low temperatures or high humidity levels. 

If your plant is experiencing a zinc deficiency, it will show various symptoms like chlorosis of young leaves, small dots on the leaf edges, and slowed growth of the plant. Sometimes, even the leaves may grow abnormally with the internodal distance being reduced. 

You can fix zinc deficiency by flushing your plant and washing the roots to rinse off any salt buildup in the substrate. Then, you can use fertilizers rich in micronutrients to rebuild the zinc levels in the substrate. If the zinc deficiency is severe, you can even spray zinc directly on the leaves to give your plant a quick boost. 

On the other hand, if your plant is experiencing zinc toxicity, you need to be careful — it can quickly kill your plant since it is highly toxic. And this is often caused due to iron deficiency. If your plant experiences this, wash the roots with pH-stable water and clean the substrate to restabilize the levels. 

2. Boron Deficiency and Toxicity in Cannabis

Boron problems are the second most common type of micronutrient problem you may face while growing cannabis, and since this is an immobile nutrient that is responsible for various physiological functions, a deficiency can cause various problems in the cannabis plant. 

Cannabis efficiently absorbs boron when the pH is between 5.0 and 7.0, and this mineral also helps stabilize the absorption of other elements like calcium. At the same time, if some nutrients are in excess, they can cause a boron lockout for your plant, so you need to strike the right balance for boron.

If your cannabis plant is experiencing a boron deficiency, the common symptoms include abnormal growth of new shoots, swollen roots, burns on the leaves (that resemble that of light burns), necrosis or thick leaves, etc. 

Boron deficiency is often caused due to high calcium levels in the substrate, which causes calcium borate that is not easily absorbed by the plant, excess organic matter, sandy soil with low water retention, or excess watering. 

To fix boron deficiency in your cannabis plant, add one tablespoon of boric acid to four liters of water and feed it to your plant. 

On the other hand, if there is excess boron in the growing medium, the leaves may start yellowing, with the borders turning necrotic or brown. Boron toxicity is not common and generally happens when you use pesticides rich in boron. In such cases, you must flush the roots with pH 6.0 water a few times. 

3. Sulfur Deficiency and Toxicity

Although it’s rare, sulfur deficiency can occur in soils of poor quality. But sulfur deficiency looks very similar to iron deficiency, so if you suspect either of these deficiencies, you need to verify which one your plant is facing. 

The symptoms of both deficiencies include discoloration or chlorosis of leaves on the higher tiers of the leaves. But with sulfur deficiency, the leaves will turn lime green followed by yellowish colors, and this discoloration will occur in new leaves first. The stem may also turn purple.

To fix the sulfur deficiency in cannabis plants, add more sulfur to the nutrient solution and feed it to your plant. If you are using fertilizers, ensure they are chelated, which makes the absorption of this mineral much faster. 

On the flip side, if your plant is experiencing sulfur toxicity, the plant may experience slow growth, burnt leaf tips, smaller leaves, etc. To solve this, you need to flush the substrate with water three times, followed by administering light fertilizers. 

4. Manganese Deficiency and Toxicity

Manganese is a micronutrient that manages the transportation of electrons during photosynthesis. It also forms a part of manganese protein, which makes water photolysis possible. It is also responsible for various functions like decarboxylation, energy transference, energy synthesis, etc. 

If your plant experiences manganese deficiency, it will start showing symptoms first on new leaves, which will later move onto the older leaves. At the same time, the plant may entirely stop growing. 

Generally, manganese deficiency is caused due to pH problems, so you first need to fix the pH of the nutrient solution and the substrate. Then, you must use chelated fertilizers that are rich in micronutrients. 

On the contrary, if your plant experiences manganese toxicity, the leaves may develop orange spots that turn brown eventually, along with symptoms of iron and zinc deficiencies due to nutrient lockouts. To solve this, you need to triple-flush the roots with pH-stable water. 

5. Calcium Deficiency and Toxicity

Calcium deficiency is rare, but if you ever suspect your cannabis plant is suffering from this problem, you need to look for the symptoms. Generally, calcium deficiency shows itself as yellow stains on the leaves with brown edges, which will eventually dry and fall off. 

Calcium deficiency, while rare, is serious and can kill your plant. So, if you suspect this, you need to be quick. Generally, this problem is caused due to lack of calcium in the substrate, so it can be fixed by giving your plant a calcium boost through a natural supplement like dolomite which is rich in calcium. 

6. Iron Deficiency

Another deficiency that is rare but can cause massive problems for your cannabis plant is iron deficiency. This problem generally appears on new, smaller leaves, developing chlorosis or discoloration on the leaves except on the veins. Eventually, the entire leaf will turn yellow and fall off. 

Iron deficiency is commonly found in mother plants or those that experience stress during the veggie phase due to excess training. You can avoid this problem by giving your plant an iron boost before training it.

7. Copper Deficiency 

Copper is a micronutrient that plays a macro-role in your cannabis plant’s health — it is directly related to your plant’s immune responses, especially against fungal infections. So, if your plant experiences copper deficiency, your plant may experience various fungal or mold issues, including bud rot and root rot. 

You need to catch this problem fast; otherwise, you may lose your plant within a few days if it catches fungi. To fix this, use a foliar spray that contains high levels of copper. Many fungicides are rich in copper, so you can consider using them. 

8. Magnesium Deficiency

Lastly, your plant can experience magnesium deficiency, which shows up in the form of yellow stains on the leaves with brown edges. While magnesium deficiency doesn’t have any lasting side effects, it can still be fatal for your plant if it occurs during the early flowering stage. This is the time when your plant needs the most amount of magnesium. 

But there’s nothing to worry about if you catch this problem on time. This problem progresses slowly, so once you catch it, simply give your plant a magnesium boost via Epsom salt. This should be enough to treat magnesium deficiency in most cannabis plants. 

pH and Micronutrient Uptake

The pH of your grow medium, whether you are using soil or a hydroponic setup, is a measurement of the medium’s acidity or alkalinity. If the pH is more than 7.0, the medium is alkaline; if it is less than 7.0, it is acidic. 

However, cannabis does not prefer an acidic or alkaline environment — it prefers a slightly acidic medium with a range of 5.5 to 6.5, depending on the growing medium used. 

But what does this have to do with nutrient uptake? 

Because pH is responsible for efficient nutrient uptake. At the right pH levels, the roots can easily absorb nutrients from the soil; if the pH levels are not right, the roots may entirely fail to take up some nutrients or even experience a nutrient lockout or deficiencies. 

As you have already seen above, most micronutrient deficiencies are related to pH problems in one way or another. 

So, it is recommended that you check the pH and TDS/EC of your nutrient water and the growing medium regularly to ensure the roots have the right environment around them for efficient nutrient uptake. 

To do this, invest in a pH meter — even the cheap ones are reliable. Then, measure the pH of your nutrient solution and the runoff water from the container drainage. You are good to go if the two readings are similar and within the recommended pH levels. 

In some cases, the pH of the nutrient solution may not be within the recommended range. Here, you can use a pH up/down solution to regulate the pH.

On the other hand, if the two readings are not similar, it might be due to salt buildup in the growing medium. In that case, you must flush your plant with RO or pH-neutral water to wash off all the salts. 

Summary: The Importance of Micronutrients for Growing Cannabis: A Detailed Guide

If your cannabis plant is Middle Earth, think of micronutrients as the Hobbits. Small but important enough to destroy the Dark Lord Sauron and restore peace to Middle Earth. And when growing cannabis, you must hold micronutrients in just as high regard as Tolkien held for hobbits. 

Keeping the analogy aside, micronutrients are essential for your plant’s growth. Even in minuscule quantities, micronutrients make various processes of your plant possible, ranging from photosynthesis, protein synthesis, and immune responses to seed germination and bud production. 

They are what make these processes possible, and without them, even macronutrients become useless. So, always ensure you use the right nutrients and water that contain the necessary micronutrients. 

And if you notice any symptoms of micronutrient deficiency or toxicity in your cannabis plant, act quickly. Do not make the mistake of ignoring the symptoms just because “Oh, they are just micronutrients — who cares?”

If you want to grow a healthy cannabis plant that yields terrific buds, focus on the micronutrients just as much as you would on macronutrients. And for even better results, stay tuned to our blog. We post grow guides regularly that go into various aspects of growing healthy cannabis plants.