Cannabis plants require the micronutrient boron to aid vegetative and reproductive growth. Boron in both water-soluble and insoluble form should be present in your growing medium or nutrient fertilizer. Lack of boron is a common deficiency in cannabis plants and can be recognized by grey or brown dry spots on leaves.
Alternative Way To Fix Boron Deficiency?
Boron deficiency looks similar to calcium deficiency but only presents in new growth, which is slower and deformed in comparison to healthy plants. Boric acid and Solubor amendment for soil or nutrients is the best way to fix the problem. However, a good alternative is top dressing with substitute decomposing organic matter such as homemade compost.