Common Cannabis Nutrient Deficiencies Caused By Incorrect pH

Getting the pH right is like finding the perfect balance for your cannabis plants to absorb all the nutrients they need to grow well. Ignore this and you’re inviting trouble. That’s because cannabis is a picky eater and it has its preferences, especially when it comes to pH. 

pH is one of the most common reasons why your cannabis plant suffers from nutrient deficiencies, but how do you know for sure? And what nutrient deficiencies are caused by incorrect pH levels? 

Fear not! With a little know-how and some TLC, you can steer clear of these pitfalls and keep your plants happy and healthy throughout their growth cycle. Roll up your sleeves, it’s time to learn why pH is important, what nutrient deficiencies are related to it, and how to fix them. 

Process of Nutrient Absorption in Cannabis Plants

Cannabis plants, like any living being, need vital nutrients to grow and thrive. These nutrients are taken in by the plant roots from the soil or growing medium. If you want to understand more about nutrient deficiencies that can plague your plant, it's important to grasp how cannabis plants absorb nutrients to ensure they grow strong and healthy.

The journey of absorption in cannabis plants kicks off at the roots. The roots of cannabis plants have structures called root hairs, which significantly boost the surface area for absorbing nutrients. These root hairs release enzymes and acids that aid in breaking down inorganic compounds in the soil, making it easier for the plant to access these elements.

Once the nutrients are dissolved in water within the soil they can be taken up by the roots through osmosis. Osmosis is nothing but a process where dissolved nutrients and water move from areas with high concentrations to lower concentrations. Meaning, it moves from the soil to the root cells. This movement is made possible by transport proteins in the membranes of root cells.

Cannabis, like most plants, needs a variety of nutrients for survival. They are divided into macro and micronutrients. While macronutrients include Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) and Sulfur (S), micronutrients consist of Iron (Fe) Zinc (Zn) Manganese (Mn) Boron (B) Copper (Cu) and Molybdenum (Mo). These nutrients play roles in processes like photosynthesis, enzyme activation, and maintaining the plant's structure.

Various factors impact nutrient uptake in cannabis plants, and pH is one of them. When the pH deviates from the range, certain nutrients may become less accessible leading to deficiencies or toxicities. Environmental factors such as temperature, humidity, and light intensity also influence absorption.

Why pH Matters for Cannabis Plants?

Cannabis, even if it is native to high-altitude deserts, is a demanding plant for growers. One such demand is that the growing medium or the nutrient solution must be slightly acidic — only then will the roots absorb the nutrients properly. This is why perhaps the most common cause of nutrient deficiencies in cannabis plants is down to incorrect pH levels. 

But what exactly is pH and how does it matter for your cannabis plant? pH refers to the acidity or alkalinity of a solution. pH is short for the potential of hydrogen, ranging from 0 to 14.0. In simple words, it’s the concentration of hydrogen ions in a particular solution; it gives you a look into how chemical compounds interact with each other as per their ionic state. 

If the solution is lower than 7.0 pH, it is acidic, and if it is higher than 7.0, it is alkaline. A solution with 7.0 pH is neutral; think deionized or RO water since they lack hydrogen ions entirely. Maintaining the right pH range is vital for the well-being of plants. If the growing medium becomes too acidic due to low pH levels, it can result in deficiencies that hinder the plant's ability to take in necessary elements.

Here’s the thing: the pH scale is logarithmic, so even small changes in the value cause significant differences in the acidity or alkalinity of the solution. For instance, a pH 3.0 solution is ten times more acidic than a pH 4.0 solution! 

Correct pH vs Incorrect pH for Cannabis Plants 

If the pH of your growing medium or nutrient solution is ideal for your plant, your plant will absorb the nutrients properly. This leads to proper plant growth with your cannabis growing taller with more vigor. 

On the other hand, if the pH is incorrect, the roots may fail to absorb some or all nutrients. In some cases, incorrect pH can even make the roots absorb specific nutrients more than the rest, causing all kinds of nutrient issues, including deficiencies. 

Incorrect pH creates an antagonistic condition for nutrients by inhibiting the functioning of various biochemical pathways in the roots. The result is nutrient deficiencies or imbalances. 

Common Nutrient Deficiencies Caused by Low pH 

There are two types of pH issues your plant may face: too high or too low pH. Let’s tackle the latter first before moving on to the next one. If your cannabis plant is suffering from nutrient deficiencies from low pH, it will show distinct signs, which are as follows:

• Brown spots on the leaves, especially on those that are exposed to direct light 
• Red, pink, or purple coloration on the leaves along with yellow spots 
• Some leaves turning brownish-yellow 
• Some leaves develop a red-brown tint on them 
• Leaves may look old and withered but won’t drop 

These are the typical signs of low pH causing nutrient deficiencies in a cannabis plant.

The most common nutrient deficiencies caused by low pH are:

1. Phosphorus 

Some of the issues arising from low pH levels in growing cannabis include the lack of phosphorus a key nutrient for cannabis plants. Phosphorus is vital for plant functions such as photosynthesis and also for energy transfer. Although a growing medium with low pH will not cause phosphorus deficiency directly, it can make the environment acidic, making it challenging for the plants to absorb phosphorus effectively. 

When the environment around the plant, i.e., the growing medium becomes very acidic, the availability of phosphorus in the soil decreases significantly. This decrease happens as there's a chemical reaction between the components of the soil and phosphorus ions, which hinder the nutrient's ability to dissolve and be taken up by plant roots. Consequently, cannabis plants grown in low pH settings may struggle to get phosphorus even if phosphorus is present in the soil.

Suffice it to say that low pH levels can make phosphorus deficiencies worse and the symptoms that come with them. 

When cannabis plants face challenges in absorbing phosphorus due to low pH levels, a variety of symptoms may appear, indicating a worsening deficiency.

One key sign of a phosphorus deficiency is when leaves turn dark green or purple. This unusual color change is linked to disruptions in chlorophyll production and pigment buildup leading to a leaf coloration.

Typically, with phosphorus deficiency, you may notice that the plant has weakened stems, making them more prone to bending or breaking. This issue becomes more pronounced if the growing medium is too acidic or has low pH, resulting in weaker stems that struggle under even slight pressure.

Also, remember that phosphorus deficiency often coincides with deficiencies like iron and manganese which are also worsened by low pH levels. When multiple nutrient deficiencies occur simultaneously, they can impede plant growth and exacerbate stress on cannabis plants.

2. Calcium 

Calcium (Ca) plays a major role as a nutrient for cannabis plants contributing to various essential processes such as cell wall formation,  maintaining membrane integrity, and activating enzymes.

The chances of low pH resulting in calcium deficiency are rare, but it can occur as acidic conditions can prevent the plant from absorbing adequate amounts of calcium. If you see abnormal growth patterns where the plant looks stunted, it could be a sign of calcium deficiency. Specifically, look at the tips of the leaves as they could appear brown or curled. Leaves may curl upwards or downwards along the edges accompanied by brittleness and reduced flexibility, which occurs as a reaction to stress. 

If the growing medium is very acidic, the plants may struggle to intake calcium. Low pH levels can increase the solubility of a few soil components, so the ions present in the root area get washed away. In addition, acidic surroundings can disrupt the intake and movement of calcium through plant roots, worsening symptoms related to calcium deficiency.

When cannabis plants face a calcium deficiency worsened by pH levels, various distinct symptoms may appear, indicating issues with calcium absorption. 

Even the leaves grow abnormally with curling and cupping leaves, while stems could look twisted or deformed. 

The leaves may also display necrotic spots at the tips or edges. These brown or blackened areas may spread gradually across the leaf surface if the deficiency persists. Necrosis occurs as cell membranes and tissues break down due to cell death caused by calcium deficiency.

3. Magnesium 

Magnesium is yet another important nutrient, and just like many other nutrients, an acidic medium can prevent the plant from absorbing enough of it to function. It is vital for key processes like photosynthesis, enzyme activation, and chlorophyll synthesis. 

Symptoms of magnesium deficiency include yellowing of leaves despite the veins looking intact — a condition referred to as interveinal chlorosis. As the deficiency worsens, the leaves may develop purple patches before wilting away. If the deficiency becomes very severe, the leaves may start dying, affecting the entire plant as the leaves are no longer capable of conducting photosynthesis. 

Low pH can affect the mobility and solubility of ions present in the soil solution, making it harder for plant roots to access this nutrient. Moreover, acidic settings can disrupt the mechanisms for absorbing and transporting magnesium to plant roots, further worsening symptoms of magnesium deficiency.

When cannabis plants face exacerbated magnesium deficiency due to low pH levels, they may exhibit telltale signs including interveinal chlorosis. This is because magnesium plays a major role in producing chlorophyll and maintaining pigment stability. When there is a lack of magnesium, the production of chlorophyll is affected, leading to the yellowing of leaves.

If you don't correct the pH, the problem worsens further and the leaves may even show signs like brown or purple spots appearing on their surface. These spots indicate localized tissue necrosis or cell death showing how magnesium deficiency can harm plant function and structure.

4. Molybdenum 

Molybdenum (Mo) serves as a micronutrient for various enzymatic functions in plants. Not only does it help with nitrogen metabolism but also aids in the transformation of inorganic phosphates into organic compounds. It's not common to experience molybdenum deficiency, so you'll not hear many growers talk about it; however, if you don't manage the pH properly, you'll perhaps see it for the first time in your cannabis plants. 

When cannabis plants face intensified molybdenum insufficiency due to acidic pH, they may display a variety of symptoms indicating challenges with molybdenum uptake and utilization. One sign is chlorosis or yellowing of leaves which becomes particularly noticeable in younger leaves or newer leaves. So the top part of the plant will display these symptoms. 

Sometimes chlorosis can also cause the leaves to curl or they may start cupping, indicating a disruption in their growth.

Molybdenum deficiency can hinder the growth of plants in such a way that they grow small compared to healthy ones. The plants look weak and dull with stunted shoots. 

Also, you may notice issues with flowering as insufficient molybdenum can disrupt the flowering and reproductive processes, leading to irregularities in flower development and seed production. Affected plants may show flowering patterns with smaller flowers than their healthy counterparts.

The plants may also be more vulnerable to stressors such as pests, diseases, and unfavorable growing conditions. This increased susceptibility is due to weakened plant defenses and impaired metabolic processes that make them more prone to the effects of stressors on their health and productivity.

5. Nitrogen (sometimes in soil)

Nitrogen is one of the main, most important macronutrients necessary for cannabis plants to grow well. It aids with photosynthesis, protein production, and overall metabolism. While nitrogen deficiency is an issue during the vegetative phase, having low pH levels in the growing medium can worsen this problem leading to negative impacts on plant health.  

As you already know, acidic environments prevent plants from taking up adequate amounts of nitrogen because the solubility is affected. Also, acidic growing mediums can affect soil microbes that are responsible for converting nitrogen, making the situation worse. 

Coming to the symptoms, the most common sign is yellowing or chlorosis of mature leaves. This is because of a reduction in chlorophyll so the leaves are unable to conduct photosynthesis efficiently. 

Since nitrogen is very important for the formation of lush foliage and strong stems, you'll notice that the leaves and stems look dull and stunted overall. When the nitrogen levels are reduced, plants might not be able to defend themselves against various issues and could struggle to handle stress making them more susceptible to pest attacks, fungal diseases, and other health problems. 

6. Sulfur (sometimes in soil)

Sulfur helps in various biological processes such as making proteins, activating enzymes, and forming chlorophyll. Sulfur deficiency isn't common in cannabis cultivation, but just in case it happens, you can observe several symptoms, including leaf chlorosis while the veins retain their green color. The difference between sulfur and nitrogen deficiency is that the young growth gets affected first with sulfur deficiency. 

Sulfur deficiency can also impact the chemical composition of cannabis plants, altering their taste and aroma profiles. Sulfur-containing compounds are responsible for the taste and smell of flowers and a lack of them can lead to a final product that lacks desirable aromatic properties.

7. Potassium (sometimes)

Potassium helps with regulating osmosis, transporting nutrients, and also with activating enzymes. Potassium deficiency is fairly common in cannabis plants but it can worsen if the pH levels are super low. 

When cannabis plants suffer from potassium deficiency exacerbated by pH levels they may show distinct symptoms. A key sign of not having potassium is when the edges of leaves turn yellow or brown. Initially, these affected areas may show signs of discoloration that can eventually lead to tissue death and necrosis over time. This issue usually starts at the tips or edges of older mature leaves before spreading.

The leaves may either start curling or cupping and look abnormal, indicating disruptions in cell turgor pressure and water balance caused by a lack of potassium.

When cannabis plants lack potassium, it can weaken their structure, making them more prone to bending or breaking. This may result in feeble stems compromising the plant's stability.

Potassium is crucial for flowering, so you can see a decrease in flower formation. You may notice that the buds look small and stunted too. Moreover, potassium deficiency may impact seed development and viability, ultimately lowering germination rates.

Generally, these nutrients are best absorbed on the higher end of the ideal pH range of your cannabis plant. So, if you notice these symptoms, check out our guides on nutrient deficiencies and how to fix them. 

Common Nutrient Deficiencies Caused By High pH

On the other hand, if your cannabis plant is suffering from nutrient deficiencies from high pH, it will show the following symptoms:

• Yellow stripes or spots on the leaf's margins 
• Brown spots developing on the lower leaves of the canopy 
• Edges of the leaves turning yellow 
• Leaf tips wilting 
• Some leaves develop bluish coloration on the surface 
• Some stems turn purple and, sometimes, reddish 

The most common nutrient deficiencies caused by pH being too high are:

1. Copper

Copper deficiency is rare and the plant doesn't even need it in large amounts. Still, there can be a deficiency if the pH levels rise more than the ideal levels. 

Signs of copper deficiency due to pH might include drooping, curling leaves, and the growth of misshapen leaves. If you don't resolve the problem soon, tissue death or necrosis could occur at the leaf tips and edges. Although the plant needs copper in tiny amounts, a deficiency can make the plants weak and affect their vitality. Therefore, it's important to choose nutrients that offer a balanced blend of both macro and micronutrients. 

2. Iron

Iron, despite being a micronutrient, is one of the most crucial elements for cannabis. Without it, the plant will struggle to perform important metabolic functions necessary for survival. 

One obvious sign of iron deficiency is that the younger leaves turn lime green in color. As the deficiency worsens, the older leaves may also be affected. The leaves will look stunted and may also develop patches. 

3. Boron 

Boron deficiency in cannabis plants can arise when the pH of the soil is so high that the plants cannot absorb it. Of course, a deficiency typically occurs when the soil doesn't contain enough boron, but since we are talking about the pH here, the deficiency will happen even if the soil has enough boron. 

One sign of a lack of boron is when the stems look brittle and thick with distorted or necrotic growing tips. The new growth will appear stunted and the plant will struggle overall. 

Furthermore, a shortage of boron can result in issues with flower formation, so the yields can be less than you expect. To tackle boron deficiency caused due to high pH, you should first adjust the pH and then add supplements containing boron. 

4. Manganese (especially in hydroponics)

Cannabis plants can display manganese deficiency when the pH levels rise so high that the roots cannot absorb it efficiently or when the soil doesn't contain sufficient amounts. Symptoms of deficiency often include chlorosis, where the tissue between leaf veins turns yellow while the veins remain green. In severe cases where you fail to identify and correct the problem, necrosis or tissue death may occur, typically starting at the edges of leaves. 

As always, adjust the pH first and then add balanced nutrients containing all macro or micronutrients or you can add supplements containing manganese.

5. Phosphorus (in hydroponics or coco plants)

We already discussed how phosphorus deficiency can occur when the pH is too low; however, the reverse can happen if you're growing in hydroponic mediums, meaning you can observe phosphorus deficiency when the pH is too high. The symptoms will be the same, but you'll have to decrease the pH here instead of increasing it. 

If the growing medium experiences constant fluctuations in pH where it increases and decreases rapidly, you will need to inspect it first to figure out why it's happening. Symptoms of nutrient deficiencies look similar to pH issues because they are interconnected. Therefore, recognizing why the problem is occurring is important to solve it. 

These nutrients are best absorbed at the lower end of the ideal pH spectrum, so if the pH rises too much, it can lead to such nutrient deficiencies. 

Again, it is wise to know that this is merely a rough guideline to help narrow down your search for the culprit. You should always double-check the symptoms to find the particular nutrient deficiency instead of jumping the gun with a treatment. 

How to Test if it’s the Wrong pH Causing Nutrient Deficiencies?

Caution is key when it comes to anything cannabis related. Otherwise, you may end up solving a problem that doesn’t exist, which may lead to a new problem entirely. So, you need to check if it’s the wrong pH that’s causing nutrient deficiency and not anything else. 

To check these, follow these tips:

• Either the irrigation water/nutrient water or the runoff water will have the wrong pH, indicating salt buildup in the medium 
• Test the pH of your nutrient water with a pH pen — it should be between 5.5 to 6.5
• Correct the pH if necessary (more on this later)
• Water your plant with this solution 
• Check the pH of the runoff water — it should be the same or at least in the same ballpark 
• If it’s not the same, there is a salt buildup in the growing medium that’s fluctuating the pH 

That’s it. 

Still, it’s a good idea to learn about other possible reasons for the nutrient deficiency in your cannabis plant, such as:

• Not enough nutrients to begin with or not in the right ratio, at least 
• Too many nutrients or supplements 
• Presence of non-compatible nutrients in the solution 
• Incorrect watering routine 
• Too hot or cold growing conditions 
• Excess light 

What’s the Ideal pH Range for Cannabis Plants?

Before we get to fixing this issue, let’s learn the ideal pH range for your cannabis plant. Refer to this:

• 5.5 to 6.5 in hydroponic or coco coir plants 
• 6 to 7 in soil-based plants 
• 5.8 to 6.2 is the ideal range for most cannabis plants 

How to Fix the pH of Your Cannabis Plant?

Now that you’ve figured out the issue, let’s fix it. Your first step should be to correct the pH of the growing medium and the nutrient solution. Let’s begin with the solution first. 

To fix the pH of the nutrient solution, you need to first test the pH with a pH pen. It is easy to use and cheap to buy, so don’t ignore it. If the pH is too low, use a pH Up solution, and if it is too high, use a pH Down solution. Remember to be conservative and go slow, especially with the pH-down solution. Sometimes, even a single drop can do the trick! 

Next, you need to flush the growing medium. How do you do that? Water your plant a few times with RO water to remove any salt buildup within. You can do this 3-4 times without any issues. Once you’ve flushed it, test the difference in pH between the irrigation water and runoff water. 

Remember, after flushing, you should allow the growing medium to dry adequately to avoid drowning the roots. Ideally, you should only water your cannabis plant if the top inch of the soil is dry. 

Finally, don’t forget to fix the core of the problem — what must’ve caused it in the first place. Double-check your nutrient solution, concentration, and ratios. It should be in the ideal range and as recommended by the manufacturer. Overlook this part and the problem will come back to haunt you. 

Summary: Common Cannabis Nutrient Deficiencies Caused By Incorrect pH

There you have it! Navigating the pH landscape in cannabis cultivation may seem daunting at first, but it need not be. With the right knowledge and a bit of patience, you can learn the mysterious ways of your cannabis plant. Over time, this can even become second nature to you, making you into a highly competent cannabis grower. 

You must stay vigilant, though, by monitoring the pH levels and making adjustments when necessary — on time. This will help you ensure your cannabis plant is thriving with vigor and producing top-notch buds. 

So, whether you are a new grower or an experienced one, remember that pH management is one of the cornerstones of growing cannabis. Use this guide to figure out how pH is affecting your plant and get on to fix it.