How to Fix Underfeeding and Overfeeding Cannabis Plants?

Growing cannabis can be a real labor of love, and just like any living thing, it needs the right nutrients to thrive. You wouldn't feed on a handful of candy before running a marathon, right? Similarly, your plant also can't grow well without the right nutrients. 

You want to give them the fuel they need to perform at their best. That's where understanding overfeeding and underfeeding comes in. We're going to dive into the signs and symptoms of both so you can keep your plants healthy and happy and avoid those nutrient issues.

Understanding Cannabis Nutrient Requirements

Cannabis plants need a variety of important nutrients to grow. These nutrients are generally divided into two classes of nutrients i.e. macronutrients and micronutrients and are super important for cannabis plants.

Primary Macronutrients

• Nitrogen helps the plants grow and develop color and leaves with greater yield.
• Phosphorus is vital for root growth, flowering, and transferring energy throughout the plant.
• Potassium helps to improve overall plant health, allows better stress tolerance, and enhances the quality of flowers and buds.

Secondary Macronutrients

• Calcium helps strengthen cell walls, aids in nutrient absorption, and prevents issues like tip burn.
• Magnesium improves plants' resistance to diseases and droughts.
• Sulfur helps to produce proteins and enzymes.

Micronutrients

Micronutrients are needed in small quantities but are equally important to cannabis.  The deficiencies of such nutrients are often expressed subtly, like interveinal chlorosis or lack of vigor. Micronutrients and their roles include:  

• Iron is essential for chlorophyll synthesis and enzymes.
• Zinc helps in making growth hormones and enzymes.
• Manganese helps in photosynthesis and nitrogen metabolism.
• Copper is essential for photosynthesis and reproductive development.
• Boron helps in strengthening cell walls and also with pollination. 
• Molybdenum is useful in turning nitrates into useful forms of nitrogen.

What is Overfeeding While Growing Cannabis?

Your plant needs a lot of nutrients, whether you're talking about micro- or macro-nutrients. It's essential for its growth, potency, and yield it produces. But too much isn't always a good thing, and the same applies to cannabis plants.

Giving your plant more nutrients than it needs can backfire and can do just as much damage as not feeding it enough. When you overfeed your plant, it leads to a nutrient burn or toxicity, overwhelming its system and leading to various issues. 

So, how do you figure out if you're overfeeding your plant? By understanding the right signs of nutrient burn or toxicity. This can help you avoid overfeeding your plant and maintain its health. Let's dive in with these symptoms and how to fix them.

1. Burns on the Leaf Tips 

A symptom that is usually the first to arrive and also the most recognizable when it comes to overfeeding is burn marks on the leaf tips. Here, your cannabis plant takes in more nutrients than it can handle, which leads to nutrient salts being collected in its tissues and growing medium. These excessive salt deposits end up causing chemical burns on the plant, which often begin at the tip of the leaves. 

But wait, what exactly does a leaf tip burn look like? It's simple — the leaf tips will start turning brown or yellow, and it will start in a small area but gradually start speaking out to the entire leaf as the problem worsens. Over time, this can end up turning large parts of the leaves brown and even kill them. 

Never make the mistake of underestimating this problem. It may seem small at first, but it is a major symptom that you're giving your plant more than it can handle. If you ignore this, it can quickly go from bad to worse, leading to imbalances in nutrients, slowed growth, and loss of photosynthesis. 

Solution

Time to solve it. As mentioned, leaf burn is common, but it is also most associated with nitrogen, a macronutrient that is often overfed to cannabis by new growers. To fix this, start by cutting down on the nutrients you give to your plant. 

Next, you should flush the soil to remove any excess salt buildup. You can do this with pH-adjusted water. Post flushing, give your plant some time to get back on its feet and fix your feeding routine to prevent this in the future. 

2. Leaves Turning Dark Green 

Another symptom of overfeeding your cannabis plant is when the leaves start turning dark green. This usually happens due to excess nitrogen since it is an important nutrient for your cannabis plant's growth. Too much of it can turn the leaves deep green. 

Generally, a healthy cannabis plant should have vibrant green hues, but when it gets too many nutrients, especially nitrogen, the green can deepen and turn more intense — you'll know it when you see it — and look unnatural. 

Along with dark green hues, the leaves may also get thicker, shinier, or a bit leathery. On the other hand, healthy leaves should have a soft texture. 

Dark green hues due to too much nitrogen aren't just on the surface, though. Too much nitrogen can slow down the growth of flowers during bloom as your plant starts focusing its energy on leaf development instead of flowers. 

Additionally, too much nitrogen can also interfere with the absorption of other nutrients, causing imbalances that can make matters worse for your plant. Usually, it ends up affecting the uptake of phosphorus and potassium — the other two macronutrients. 

Solution

How do you fix this? You need to start by fixing your feeding routine and giving your plant only the nutrients, especially nitrogen, that it needs. You also need to learn more about your plant's growth stages and its nutrient requirements. Look up strain information, and you'll get an idea. 

If you already notice your leaves turning dark green, it's time to cut down on nitrogen for your cannabis plant. Meanwhile, you should also make sure you're not cutting down too much on other nutrients. Usually, nitrogen-rich fertilizers are the culprits here. 

3. Leaves Curling or Clawing 

Green hues aren't the only symptom of excess nutrients, especially nitrogen; sometimes, the leaves may start curling downward or start forming what we call the claw. Essentially, this is a defense mechanism of the plant kicking up in an effort to avoid absorbing more nutrients than it can handle. 

When the leaves start curling, you'll notice that they'll start bending at the tip and base, much like a downward claw. In contrast, healthy cannabis plants grow toward the light and outward. The leaves may also look like they're drooping, and your plant's stems may also become weak. If you don't fix this issue on time, your leaves may start twisting in weird ways — a sign of stress. 

Speaking of stress, remember that curling leaves are a sign of stress, not just too many nutrients. Over time, the leaves may stop working properly — they will lose their ability to photosynthesize, stunting your plant's growth and development. Additionally, clawing can bring other issues like nutrient lockout and burns on the leaf tip. 

Solution 

As mentioned earlier, this problem is caused due to too much nitrogen, and you must fix it as soon as possible. Your first step should be to flush the growing medium or soil to get rid of any built-up nitrogen and nutrients. 

Next, you need to lower the nitrogen levels in the nutrient solution. It's best to be more conservative here and increase the nitrogen uptake if and when required instead of doing it the other way around. Your plant should start recovering in a few days. 

4. Slowed Down Growth

While the symptoms mentioned above are pretty direct and easy to recognize, there's one symptom that can sometimes be tricky to figure out: stunted plant growth. But don't underestimate it — it's still a sign of a serious problem that can affect your plant's health and yield. 

Your plant can experience stunted growth even when the leaves look completely fine. So, look out for your plant's vertical growth — if it slows down unexpectedly, you need to start investigating. 

In other words, if your plant starts growing smaller leaves, fewer branches, or the buds are delayed, it's a sign of stunted growth. In fact, you may notice that the plant has entirely stopped growing!

This is a serious problem because it can affect your plant's yield, and no one wants that. Essentially, when you overfeed our cannabis plant, it starts directing its energy to processing all the additional nutrients instead of growing new leaves and flowers. 

After a while, this problem can lead to fewer and smaller flowers. So, even if your plant makes it out alive, you'll still end up with a subpar yield. 

Solution

To prevent this, you need to stop overfeeding your plant. It's best to follow the nutrient routine recommended by the breeder instead of winging it. They know the strains best, and they know exactly what your plant needs. Additionally, you should also follow the fertilizer manufacturer's recommendations on dosage and administration. 

5. Locked Out Nutrients 

One of the worst things that can happen to your cannabis plant due to giving it too many nutrients is a nutrient lockout. When the nutrients build up a lot in the growing medium or the soil, it can stop the roots from absorbing more nutrients by acting as a barrier. So, even if you give all the nutrients you have at home, your plant will not be able to absorb them properly. 

The tricky part is identifying this problem. Your plant may experience a nutrient lockout of specific nutrients, and you need to look at various symptoms to figure out which nutrient is being locked out. 

However, you can look out for a few signs, including leaves turning yellow, curling or clawing leaves, slowed growth, burns on the leaf tip, or even the stems turning purple. Your cannabis plant may also show signs of specific nutrient deficiencies, even if the growing medium has all the right nutrients. 

This is what makes nutrient lockout such a serious issue. It's like your plant has the nutrients but can't use them. If you don't address this issue on time, it can quickly make your plant more stressed, slow down its growth significantly, and even affect flower development. The result? Low-quality yield. 

Usually, a nutrient lockout is caused by giving your plant too much nutrients or the pH not being in the correct range. So, if you want to avoid it, you need to maintain the right pH in your growing medium and nutrient water and make sure you never overfeed your plants. 

If your cannabis plant is already facing a nutrient lockout, then the process remains the same as above — flush off the growing medium with pH-balanced water to remove built-up nutrients and take a conservative approach to feed your plants. 

What is Underfeeding While Growing Cannabis?

With overfeeding out of the way, let's take a look at underfeeding, i.e., not giving your cannabis plants enough nutrients to begin this. Like overfeeding, this can also significantly affect your plant's health, yield, and growth. 

When your plant does not get all the right nutrients in proper quantities, it can start to experience stress, which can show up as a variety of nutrient deficiencies. 

Remember, each nutrient plays a particular role in your plant's growth and health, and if your plant misses out on even one nutrient, it will show signs of nutrients. As a result, your plant may experience stunted growth and poor bud development. 

Let's dive into some symptoms of nutrient deficiencies and how you can fix them. 

1. Leaves Turning Yellow or Chlorosis 

Perhaps the most common symptom of nutrient deficiencies is chlorosis, where the leaves start turning yellow. This problem usually starts in the older leaves that are lower in the foliage, especially when your plant is missing out on nitrogen. 

Cannabis uses nitrogen during the production of chlorophyll, which helps capture sunlight and gives the leaves its green color. When your plant experiences nitrogen deficiency, the leaves fail to produce enough chlorophyll and start losing their green color. 

As a result, your plant will fail to produce more energy, experiencing stunted growth and, in severe cases, even death. In any case, if you let this problem persist for long, it can significantly affect the yield of your cannabis plant. 

But why older leaves? That's because when your plant experiences nitrogen deficiency, it focuses its energy on newer leaves by pulling nitrogen, a mobile element, from older leaves. 

That's not all. This chlorosis often begins at the edges and tips of the leaves and grows inward. If not addressed on time, this problem grows inward and may turn the entire leaf yellow and even cause it to fall off. 

Solution 

So, how do you solve this problem? Fortunately, it's easy. Nitrogen is the most important nutrient our plant needs during its vegetative phase, so you just need to make sure you're giving it a well-balanced nutrient solution with plenty of nitrogen in it. 

If your plant experiences nutrient deficiency and you see signs of chlorosis on the leaves, you can start using a nitrogen-rich amendment or compost to fix it. You should also check the pH of your growing medium and nutrient solution — sometimes, nutrient deficiencies are nothing but nutrient lockouts! 

2. Stems Turning Red or Purple 

Underfeeding can also show up as purple or red stems. But unlike the problem pointed out above, this one does not come from nitrogen but phosphorus deficiency. This element is crucial for the development of rots and flowers, and energy transfer, particularly during the bloom stage. 

Just make sure you don't confuse this with strains that naturally produce purple or reddish hues on the buds and stems. If you suspect a phosphorus deficiency, first check if you're growing purple cannabis and then look for other symptoms that may show up with this. 

Usually, this symptom of purple stems starts in the leaves and makes its way to the main branch. You may notice this problem more if you live in a colder region because your plant's ability to intake phosphorus can sometimes get affected by cold temperatures. 

And if you don't fix this problem on time, your cannabis plant will experience slow growth, especially during the bloom stage. When it does not get enough phosphorus, it can struggle to grow strong roots and bushy flowers, leading to a subpar yield and a weak plant. It's a lose-lose situation. 

Unsurprisingly, phosphorus deficiency most commonly occurs when cannabis transitions from the vegetative to the flowering stage. During this transition, you need to increase the plant's phosphorus intake, and if you fail to do so, your plant may experience phosphorus deficiency. Sometimes, it can also be caused due to improper pH levels in the soil.

3. Stunted Growth 

Another symptom of nutrient deficiencies is stunted growth, where the plant grows slowly since it is not getting enough nutrients to sustain itself. Remember, cannabis needs many nutrients, from nitrogen and phosphorus to calcium and magnesium, to grow properly. When they are not available, it can lead to stunted growth. 

When your cannabis plant suffers from stunted growth, it will start looking smaller than what you'd expect it to be. Plus, the stems may grow thin, and may not have lush foliage. It will also lose its vigor. 

In severe cases, your cannabis plant may stop growing new leaves or buds entirely and start stagnating. The growth may also turn spindly, and your plant may lose its strength to hold itself up, especially during bloom, and may fold on itself. 

As a result of this, your plant will fail to reach its full potential, and you'll end up with a poor yield. This problem gets especially worse during the flowering stage when vigor and strength are crucial for a good yield. Plus, let's not forget — a weak plant is a paradise for diseases and insects. 

Solution

To solve this problem, you need to understand its cause: a general lack of nutrients. So, you need to start by fixing your plant's nutrient regime and start giving it a balanced diet. You should also study other symptoms closely to figure out exactly which nutrients are lacking for your cannabis plant. 

It's also time to recheck the growing medium to make sure it is airy and has good drainage. This supports good development of the roots, which is crucial for nutrient absorption. 

4. Deformed Leaves

Finally, another major symptom of nutrient deficiencies in cannabis is the deformation of leaves. This is where the leaves start curling or twisting, and it is commonly caused by a lack of sulfur or calcium — both crucial for healthy root and leaf growth. Calcium helps the cell walls get stronger and sulfur helps in amino acids and protein production. 

This deformation of leaves usually starts on newer leaves and at the top of the plant. Plus, you may notice the leaves shriveling or getting crinkled. Some leaves may even start developing tears and holes. 

Usually, sulfur and calcium deficiencies are caused by poor soil quality or incorrect pH levels. If not that, then the next common cause is just an imbalanced nutrient solution. 

Solution 

To fix this issue, you need to start by checking the pH of the soil and nutrient solution. Next, check the growing medium — it should be airy and have decent drainage. Finally, fix the nutrient routine and solution. 

In the case of calcium, magnesium can sometimes interfere with its absorption, so make sure the nutrient solution does not have excess calcium. Your best bet is to use CalMag solutions here, as they have the right ratio of the two elements. 

What is the Difference Between Overfeeding and Underfeeding?

1. Visual Indicators

Overfeeding (Nutrient Burn)

• The most common signs of overfeeding could appear as burnt or brown leaf tips, also known as nutrient burn. 
• Excess nitrogen makes the leaves too dark, which is also a sign of overfeeding.
• If leaves begin to curl downwards like a claw, this means that the plant has become stressed from nutrient toxicity.
• Finally, if you see white or crusty stuff on top of the soil, it means there is too much salt building up from fertilizing too much.

Underfeeding (Nutrient Deficiencies)

• When there is a deficiency of nitrogen or other nutrients, the leaves start turning yellow, starting with the older ones.
• When a plant lacks enough phosphorus and sometimes magnesium, its leaves or stem will go reddish or purple.
• Leaves may be smaller, pale, or dull, indicating less nutrient uptake.
• You may also notice some interveinal chlorosis (yellowing between leaf veins), which is a classic indication of magnesium or iron deficiencies. 

2. Growth Patterns and Plant Health

Overfeeding

• An overabundance of nutrients can overload the root system, limiting the uptake of nutrients and preventing growth.
• Many nutrients overload the roots and prevent them from taking nutrients from the soil. 
• Too many nutrients can damage roots which may end up burning or causing a root zone imbalance.

Underfeeding

• Plants can be weak and spindly when they cannot find the nutrients they need for healthy growth.
• Your soil may not provide adequate nutrients required for your plants to bloom. 
• If plants are chronically underfed, then leaves can drop off prematurely and further reduce photosynthesis.

How to Properly Balance Nutrients? 

Overfeeding and underfeeding can have severe effects on your cannabis plant, leading to stress, subpar yield, and poor health. So, you need to restore balance quickly after your plant experiences a nutrient lockout or deficiency. Here's a short guide on how to do that. 

Fixing Overfeeding by Flushing the Medium

If your plant has experienced overfeeding, the solution begins with flushing the growing medium to remove all the built-up salts from it. Follow these steps to properly flush your plant:

1. Pour pH-balanced water generously on the growing medium until it all runs off — you need to use 2 to 3 times the total volume of your plant's container
2. Test the pH of the runoff water to make sure it is proper 
3. If the pH is off, you can use pH up/down solutions 
4. Post flushing, start feeding your plant a mild dose of rebalanced nutrient solution and gradually increase the dosage 

Fixing Underfeeding by Adding More Nutrients

On the other hand, if your cannabis plant is suffering from nutrient deficiency, you need to introduce more nutrients to it gradually. Here's how to do that:

1. Figure out exactly which nutrient your plant is lacking by studying the symptoms 
2. Increase that particular nutrient gradually, starting with a mild dose 
3. Don't forget to check the nutrient ratios since excess of some nutrients can hamper the absorption of others 
4. Give your plant time to recover 

Finally, Focus on the pH at All Times

Consider investing in a pH meter — it is one of the best things you can buy while growing cannabis. pH is super important for nutrient uptake and if it is not within the right range, your plant may either absorb too much of one nutrient or not enough of the other — sometimes, both! 

A pH meter fixes this problem. It allows you to monitor the pH easily and more accurately than pH strips. You can fix the problem before it starts affecting your plant's growth and yield. Remember, prevention is always better than cure!

How to Prevent Over and Underfeeding Cannabis Plants?

Here are a few things to keep in mind to prevent over and underfeeding cannabis plants. 

Set up a Routine for Feeding

To keep your cannabis healthy, it needs a consistent feeding schedule to avoid nutrient stress. A feeding schedule must match the growing stages and environmental conditions of your plant. 

For example, if you're growing in soil, feed every other day or every third day, depending on soil drainage, size of plant, temperature, etc. Most importantly, follow the instructions from the manufacturer and you will be fine. Let the top inch of the soil dry out slightly before watering again to prevent overwatering or nutrient lockout.

If you're using hydroponic systems, provide nutrients according to the system you're using. For example, aeroponic systems will feed the plant several times in a day whereas a DWC will not do that. Your job is to replenish the nutrients as and when you see fit. 

Environmental Considerations

Change the feeding frequency based on humidity, temperature, and light intensity. This is because plants may need more water if you use super strong lights. 

When the temps are high, the rate of transpiration accelerates, and the plants end up taking more nutrients, which might lead to overfeeding if you're not careful. On the other hand, if the temps are cooler than required, it slows down the growth and the plants don't absorb as many nutrients too. 

Coming to light intensity, plants growing under high-intensity lights will need more nutrients due to higher photosynthesis and growth rates.

Next, consider the humidity. In high-humidity conditions, transpiration slows down, reducing nutrient uptake. On the other hand, the water uptake increases in low-humidity conditions.

Keep an eye on your plants for any discoloration or curling of the leaves and feed accordingly. Your goal is to simply keep the conditions optimal. 

Adjust for Growth Stages

The nutrients vary slightly for each stage of cannabis growth. For example, provide a light feed (EC 0.4 to 0.8 or 100 to 250 ppm) during the seedling stage. Heavy feeding will hurt the roots. Instead, keep it light to help the plant establish a dense root system later on. 

During the vegetative stage, add more nitrogen slowly as this macronutrient is important to support leafy growth. Keep it between 1.0 and 1.6 (or 500 and 800 ppm). As the plant progresses to the early flowering stage, cut back on nitrogen a bit and boost phosphorus and potassium for flowering. Keep the EC between 1.6 and 2.0. 

And, finally, as the plant moves to its late flowering stage, it's best to increase phosphorus and potassium for better bud size, density, and quality. Also, cutting back on nitrogen can minimize the chance of producing harsh-tasting buds. EC should be between 1.6 and 2.2 or 800 and 1100 ppm at this point. 

During the last couple of weeks, you can flush the plant with double the amount of water. Some users say that this improves the taste of the buds; however, this is completely optional. 

Use Good-quality Water

Whether you grow in soil or in hydroponics, the quality of water is critical to cannabis growth, as it affects nutrient absorption, plant vitality as well as yields. If your water quality is poor, the plants may experience nutrient deficiencies and even toxicities as the minerals interact with one another. In short, the water quality may influence the pH, EC, and other factors. 

You can use tap water to water the plants; however, make sure you let it sit outside in a bucket for at least 24 hours to allow the chlorine to dissipate. If you use well water or some untreated source, check periodically for contaminants such as heavy metals, bacteria, or high salt levels.

Also, try and use soft water. Hard water contains large quantities of calcium and magnesium salts. These minerals are useful in small amounts but large quantities can create an imbalance. 

Also, remember that good-quality water keeps nutrients in soluble form. Bad water can cause nutrients to solidify and there can be an imbalance again. Needless to say, plants that are grown with clean water tend to have greater yields and better quality buds that have more flavor, aroma, and cannabinoids.

Summary: How to Fix Underfeeding and Overfeeding Cannabis Plants?

Finding the sweet spot when it comes to feeding your cannabis plants is key to successful growth. Overfeeding can lead to nutrient burn and all sorts of other problems, while underfeeding can stunt growth and leave your plants looking weak and unhappy. 

By paying close attention to your plants, learning to recognize the signs of both overfeeding and underfeeding and adjusting your feeding schedule accordingly, you'll be well on your way to growing some seriously impressive cannabis. Don't forget to test the pH regularly!