Is a Boron Deficiency Affecting your Cannabis Plants?

You start to notice burnt tips and pale green leaves on some of the new growth on your marijuana plants.

These are some of the common signs of a boron deficiency in cannabis.

When at its worst it looks like major heat stress and is all gnarly looking.

At times it can be confused with a calcium deficiency due to some of the same signs of both deficiencies in the early stages.

To be sure check out more of the signs below to determine if you lack boron in your plants and how to fix it, 

Signs of Boron Deficiency

Here is listing of the most common signs of boron deficiency in cannabis.

  • New leaf growth affected first
  • Edges appear burnt
  • Pale color
  • Slow growth
  • Tips of leaves are thicker than normal
  • New shoots become burnt and twisted
  • Dark brown spots between the veins
  • Leaves become thicker and brittle
  • Tips stems grow twisted
  • Rust colored on stem appear new grow medium
  • Leaves become dark green with purple
  • Leaves will start to show signs of burnt tip

Why is boron important to cannabis?

Boron is a vital immobile micronutrient, and it’s essential to build cell walls of the plant.

During photosynthesis, boron transports the needed sugars (carbohydrates) to the root zone of the marijuana plant.


Boron also increases flower production and the formation of pollen in flowers according to Wikipedia

This could be interpreted as trichomes in cannabis plants.


Causes of Boron Deficiency

Here are the reasons for boron deficiency in cannabis:

  • High calcium levels in your plants.
  • Over watering, a common cause of a lot of deficiencies in cannabis plants
  • High humidity can be a combining factor
  • Using Tap water and supplementing with too much calcium
  • High PH levels in your growing medium

You can also run into Boron Lockout.

Boron Lockout happens when the PH is above a certain level. Causing the medium to become Alkaline for the roots.

This stop’s the uptake of boron by your marijuana plants.

Here are some PH values to watch for if they are over ​​​​these values:

When growing in soil: PH levels of 6.5 or higher

Hydro and Soil Less Mediums: PH levels of 6.0 or higher    

How to Fix Boron Deficiency

The best ways to fix boron deficiency with marijuana is:


Dry your cannabis plants out first but not overly dry


Flush your plants with PH balanced water.


Adjust the PH level in the soil or coco coir


Correct the PH level in water/ nutrients.

The best values should be in the following range:

Soil, 6.0 – 6.5 pH range. Hydro or coco coir, 5.5 – 6.2 pH range


Use a lower amount of calcium if you’re supplementing with it.


Reduce humidity, by using a de-humidifier.


Use quality nutrients for your marijuana plants


Fix your drainage situation with more holes.

Signs of excessive amounts of boron

Here are the signs of excessive amounts of boron in your plants

  • Older leaves infected with yellowing tips
  • Followed by appearing burnt and dies
  • Can happen if low PH.

How to correct excess boron


Dry your plants out first.


Flush your plants with PH balanced water

Your plants will usually recover .


Adjust the PH level in the soil or coco coir


Correct the PH level of both water/nutrients.

Final thoughts

When you have to deal with a boron deficiency in your cannabis plants.

It’s best to check the pH of your growing medium and then correct if necessary. 

Lacking boron can be caused by over watering your plants.

It’s best to dry out your plants and then flush with PH water.

Calcium may also play a role if your supplementing but is rare.

Have you had any issue with boron in your garden?

How did you recover?

Let me know in the comments

Keep Growing my friends.

image credit: Image

2 thoughts on “Is a Boron Deficiency Affecting your Cannabis Plants?”

  1. Help, im new to rdwc and my system is 8cell x 5gal.bucks.
    I use 3part gh nutes and use cal magw/iron botanicare brand. Im exp. Elongated stems to leaves. My 1st.thought low light … 5 x5 tent w/1600watt hps/mh bulbs. So i put 1more hood and lowered ballast to 75% totalling 900watts Now heat has become issue ..Now im stuck and nit sure where to go next. Is 1 600watt light sufficient light for 5×5?
    And boron

    • 600 may be enough the bud development may not be as big, you could and inccrease the airflow to cool it down or even have a n ac on the outside and suck the cool air into the tent.


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