Boron deficiency in cannabis plants

How to Spot and Correct a Boron Deficiency in Cannabis Plants


Boron deficiency in cannabis plants is a rare phenomenon unless you are severely under-watering your plants. In my long career, I have come across Boron deficiency a handful of times and they were all due to neglect or careless growing.

Now, that is not to say that Boron is unimportant or that it’s not important to know how to spot the symptoms of a deficiency. On the contrary, it is important to learn how to diagnose it early and you will soon find out that it’s quite easy to do.

boron deficiency in marijuana plants

(B) Boron: Necessary for the formation of cell walls in combination with calcium.

Deficiency: Boron deficiency results in brittle stems and poor growth. Stems may twist and split.

Toxicity: Excessive Boron will cause leaf tips to become yellow and die off.

Micronutrient: Absorbed in small to minute quantities. They are generally less well known than the macronutrients since most plant foods don’t contain them.

What Does Boron Do for Cannabis Plants?

The primary function of Boron in cannabis is to assist in the formation and strengthening of cell walls. This function is important because it helps the growth and development of robust stems and leaves.

Boron also aids in protein synthesis and the regulation of carbohydrate metabolism, facilitating the plant’s energy production. It also plays a critical role in managing the transport of sugar and starches, contributing to the plant’s resilience and yield.

But wait… there’s more… Boron also influences the development of the reproductive organs, including enhancing the potency and quality of your yield.

As you can see, Boron is quite important even though it get very little attention from the grower community.

How Does a Boron Deficiency Affect the Quality of Cannabis Plants?

Even though Boron deficiencies are uncommon, they are not to be taken lightly. A lack of Boron can wreak havoc on your plants and significantly affect bud quality and yield.

In the early stages, boron deficiency may seem relatively harmless. You will notice some yellow leaves or stunted growth but as the deficiency progresses, the leaf tips will start showing signs of browning and change texture to be thicker and deformed.

The Early Stage of a Boron Deficiency

The early stages of Boron deficiency are crucial for successful recovery. Often, the initial telltale sign of a boron deficiency is a subtle change in leaf color, usually to a lighter or yellowish hue. Unfortunately, this symptom is common to most nutrient deficiencies so it’s important to not jump to any conclusions just yet.

You may notice yellow leaves or a yellowing along the edges of the young leaves accompanied by yellow or brown spots.

You should also keep an eye out for deformed new growth such as twisted stems or curling leaves.

The Progression of a Boron Deficiency

As the deficiency progresses, the initial symptoms will worsen, and new symptoms will start to appear. The yellowing and deformities will begin to affect older leaves as well as the deficiency takes over the lower leaves of the plant.

You may also notice that the growth tips and buds begin to brown and die off.

At this point, you need to touch the plant to see if the stems have started to become brittle and possibly even feel hollow or collapsed in areas.

The Late Stage of a Boron Deficiency

In the later stages of a boron deficiency, your plants will show signs of severe growth issues. At this point, the growing tips may completely die off, causing substantial crop loss.

A prolonged deficiency of boron can lead to complete necrosis, where the plant tissue dies off, often followed by the appearance of various diseases.

What Causes a Boron Deficiency and What are Common Misdiagnoses?

Boron deficiency is typically caused by the pH in the growing medium being off balance, leading to nutrient lockout, or in some cases under-watering.

How to Fix a Boron Deficiency in Cannabis Plants

When you have diagnosed the deficiency and decided that Boron is the issue, you need to act quickly to correct the deficiency before it goes any further.

The good news is that fixing a Boron deficiency is quite easy. Firstly, check that the pH level of your soil or hydroponic solution is balanced. Boron absorption is optimal at pH levels of 6.0-6.5 in soil and 5.5-6.2 in hydroponic environments. If your pH is out of balance, you need to slowly increase or decrease the pH accordingly.

If the pH is completely off or if you suspect nutrient lockout, you need to flush the cannabis plants and reapply a balanced nutrient solution. Remember, while rectifying a boron deficiency, it’s possible to overcorrect and cause boron toxicity. So, add boron gradually and monitor your plants closely.


Learn how to spot and fix cannabis nutrient deficiencies

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