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What is Boron Deficiency and How to Fix It?

Added 29 May 2022

You have been growing your cannabis plant but suddenly notice younger leaves turning pale, curling up, or displaying burnt tips. Your plant is probably suffering from boron deficiency.

Since boron is a micronutrient, many cannabis growers tend to overlook it. But that can cause problems worse than you expect. Boron is essential for your plant's development, so a deficiency can lead to various issues that can stunt the growth or compromise the yields.

In this article, learn about boron deficiency — what it is, how to identify and fix it, and how to prevent it in the future. 

Why is Boron Important for Cannabis?


Boron is a micronutrient, like copper or iron, and your plant only requires it in small amounts. Typically, fertile soil or a rich growing medium has enough boron to satisfy the plant's needs, but your plant may not be able to intake enough boron at times, leading to various issues. 

Boron takes care of specific aspects of the plant's health, such as the following:

  • Promotes healthy cell functioning, including protein synthesis, seed production, and metabolism
  • Aids in chlorophyll production in the leaves
  • Helps build the cell walls in the plant tissues
  • Transports essential carbohydrates or sugars to the roots, promoting their development
  • Aids in flower and pollen (trichomes) development during the flowering stage

Boron's importance gives you an idea of what may happen if your plant does not get enough of it. 

What Causes Boron Deficiency?


Boron deficiency can occur due to various reasons. However, in most cases, it is caused due to improper soil conditions. For example, if your soil is sandy or has low moisture-retention capabilities, it can leach nutrients, leading to boron deficiency.

Additionally, incorrect pH in the growing medium can also cause boron deficiency. The roots fail to absorb boron (and other nutrients) properly if the medium is too alkaline or acidic. Boron uptake best occurs in a neutral pH soil.

High amounts of calcium in the substrate can also cause boron deficiency as it causes a nutrient lockout within the roots. So, using hard tap water with too much calcium can cause this problem.

On the other hand, incorrect watering routines also lead to boron deficiency. Over-watering or under-watering is a common cause. Or, it could happen if you tend to use reverse osmosis (RO) water devoid of boron. You can grow cannabis plants in RO water, but you have to make sure that you add the right nutrients since RO doesn't contain any minerals or nutrients. 

How to Identify Boron Deficiency?

Twisted cupped leaves

Fortunately, boron deficiency is easy to identify in cannabis plants. The symptoms mainly occur in areas of the plant that grow actively, like roots and young shoots or leaves. You can identify boron deficiency in the following ways.


If your plant cannot get adequate boron, the symptoms first appear on younger leaves. The first sign of boron deficiency is that the young leaves may grow curled or have thicker edges. 

New leaves may also grow weak since they are malnourished. So, if the young leaves break easily upon bending, it can be another symptom of boron deficiency. You will find this symptom occurring on new leaves at the shoot tip.

Additionally, the new leaves may also grow paler than the older ones. Boron is crucial for chlorophyll production, and a lack of it can inhibit chlorophyll production, leading to discoloration.

Lastly, veins on the leaves may also appear bumpy as boron deficiency can impact cell formation and division. 


Roots are another area where the symptoms of boron deficiency occur the most. In a boron-deficient plant, the roots may grow short and have coarse skin with wrinkles towards the ends. 

Like the leaves, the roots may also exhibit irregular thickening, making the roots look like dumbbells in some areas. This is again due to impacted cell formation in the root tissues.

Abnormal Growth

Lastly, you can also identify boron deficiency with your plant's impacted growth. Since boron aids cell division in tissues, it can affect how the plant grows, especially during the vegetative state. 

Boron deficiency also destroys the meristematic cell lines, which further worsens the problem.

Younger lateral shoots may also appear deformed or discolored (brownish or reddish). 

If you notice such symptoms, your plant is likely suffering from boron deficiency.

Other Deficiencies with Similar Symptoms

But these symptoms are also shared by various other nutrient deficiencies. For example, yellowing or discoloration of the leaves is a major symptom of chlorosis or calcium and nitrogen deficiencies. 

It is easy to get confused, but if you observe your plant carefully, you can distinguish this deficiency from the rest. For instance, nitrogen and other common deficiencies affect older leaves, whereas boron affects young leaves and shoots. 

How to Treat Boron Deficiency in Cannabis?

twisted new growth

Boron deficiency is quite straightforward to treat in cannabis plants. First, you must ensure your grow medium has adequate levels of boron and that your plant can absorb it properly to fix it. 

Start by correctly diagnosing your plant beforehand. Then, follow these techniques to solve the problem.

Check and Rebalance the pH

One of the most common causes of boron deficiency is incorrect pH in the growing medium. So, first, check the medium's pH using a pH meter. Ideally, the soil must have a pH between 6.0 to 6.5, and a hydroponic system must range between 5.5 to 6.2.

If the pH balance is off, you need to rebalance it. To do so, start by flushing your plant with pH-balanced water. Then, check your nutrient solution's pH and rebalance it. After flushing and rinsing the plant, continue giving your plant the nutrient solution with the right pH.

Check the Calcium Quantity in the Medium

Next, ensure your growing medium has the right amount of calcium, not too much. So, check your calcium supplements, if you use them, to ensure they don't contain too much calcium. You should also consider switching to soft water that contains fewer amounts of calcium.

Do not try this if your plant does not show signs of excess calcium, like red or brown spots on the leaves. Reducing calcium can lead to calcium deficiency.

Correct Your Watering Routine

You should also analyze your watering routine to ensure you are not over-watering or under-watering your plant, which can also cause boron deficiency. Only water the plant when the growing medium is dry but not too dry. 

The correct moisture levels are also essential in this case. So, ensure the humidity levels are proper. Relative humidity below 25% can cause boron deficiency. If needed, consider investing in a humidifier or a dehumidifier.

Use Good Nutrient Sources

Use the right nutrient solutions and supplements specifically designed for the cannabis plant. For example, most cannabis plants don't need boron supplements because the medium and water contain boron, but if your plant is experiencing boron deficiency, ensure your nutrient solution contains enough boron. 

Use organic, rich nutrient solutions and supplements, and always read the ingredient labels on the products your purchase. Also, ensure you follow the manufacturer's recommendations to apply them to your plant for optimal results.

Give Your Plant a Boron Boost

Lastly, you can give your plant a boron boost to make up for the lack of it. Add a tablespoon of boric acid to a gallon of water, and administer it to your plant once. 

This is an effective method of giving a boron boost, so doing it once should be enough. Your plant will exhibit a positive reaction to this, after which you can flush your plant with a commercial cannabis tonic or clean water and continue your regular nutrient and water routine.

How to Prevent Boron Deficiency?

Boron deficiency

To ensure your plant does not suffer from boron deficiency in the future, follow these tips:

  • Water your plant properly to avoid drying out, and do not over-water your plant
  • Do not administer too much fertilizer or supplements that may cause nutrient lockout 
  • Maintain the proper humidity in your grow room or tent using a humidifier or a dehumidifier
  • Always use nutrients and supplements that are formulated specifically for cannabis 
  • Avoid using supplements that work for the plant's entire growth cycle. Supplements meant for the growing phase are more effective as they offer a more accurate dosage of nutrients as per your plant's growth stage
  • Maintain the grow medium's pH levels at all times
  • Avoid using water containing too much calcium or too little boron

Summary: What is Boron Deficiency and How to Fix It?

If you use the right technique, your plant will start improving within a week. Once it has recovered from boron deficiency, you can proceed to remove the damaged leaves. Damaged leaves may hog nutrients that would otherwise be useful for other leaves. 

All you need to know is how to identify and solve boron deficiency in your plant. Using a few simple methods, you can identify this problem in your plant and distinguish it from other deficiencies, and with simple techniques, you can quickly solve boron deficiency.

Growing cannabis is rewarding, but it comes with various challenges — like puzzles. Learn how to solve these puzzles, and the rest will be easy. 



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