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Problem: A boron deficiency in cannabis is relatively rare, and is usually accompanied by other types of nutrient or pH problems.
The first signs of a cannabis boron deficiency is abnormal or thick growth tips along with brown spotting on new leaves.
With a boron deficiency, upper cannabis leaves display abnormal and/or slowed growth. Growing tips may not grow properly, may display twisted growth, and may die off. New leaves may wrinkle or curl.
Plant roots can also be affected by a boron deficiency, showing unhealthy or slow growth. Stems may become rough or hollow.
A plant with a boron deficiency may look like it has a calcium deficiency because boron is needed for the plant to properly use calcium. New growth is affected the most, and may look like it's been burnt or scorched.
A boron deficiency is often accompanied by an apparent potassium or nitrogen deficiency, as these nutrients are needed for the plant to use boron. Boron deficiencies are more likely to appear when a plant is underwatered or experiencing very low humidity (very dry air).
Solution for Boron Deficiency in Cannabis
Your plant may also exhibit signs of a boron deficiency if the pH is too high or low. Learn how to manage your pH when growing cannabis.
In soil, boron is best absorbed by the roots in the 6.0 - 7.0 pH range.
In hydro, boron is best absorbed by the roots in the 5.5 - 6.2 pH range (in hydro, it's generally recommended to keep the pH between 5.5 - 6.5, but boron specifically tends to be best absorbed below 6.2).
Boron is not absorbed well by cannabis without enough potassium and nitrogen, or if there isn't enough moisture (for example if plant is underwatered or humidity is too low). That's why it is recommended you water your plant with a regular dose of nutrients below.
A plant is more likely to show signs of boron deficiency when the humidity is very low (below 25% relative humidity in the air), so you may help humidifier may be needed if your grow room is very dry.
Please note: Boron deficiencies are more likely to happen when a grower is using heavily filtered or reverse osmisis (RO) water to feed plants, since boron is found in most tap water.
If you suspect your growing cannabis plant has a boron deficiency, flush your system with clean, pH'd water that contains a regular dose of cannabis-friendly nutrients. Old damaged growth will likely not recover. Watch plant over next few days to make sure that the problem stops spreading to new growth.
If you cannot get rid of your boron deficiency, please consult our 6-Step Cure to 99% of Cannabis Growing Problems