Nitrogen

nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away and eventually die. The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft before possibly turning crispy but ultimately falling off on their own.

Cannabis needs nitrogen to keep leaves green and make energy from light. All new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant “wants" to give those leaves priority for getting light. If new leaves aren’t getting enough nitrogen, the plant will start to take nitrogen from the older, lower leaves, so that it may give it to newer leaves. This is what causes the yellowing and wilting.

Sometimes you can get the signs of a cannabis nitrogen deficiency if the pH at the plant root zone is too low, even if the nitrogen is there. This is because when the pH at the roots is not right, your plant roots can’t properly absorb nutrients. Nitrogen is especially important during the vegetative stage of your cannabis plants. As your plants start flowering, they will need lower amounts of nitrogen.

plant nutrients of any kind will include nitrogen. If you haven’t been providing any nutrient to your plants, try supplementing your regular nutrients with a bit more nitrogen and see if the plant starts recovering.