Treating Nutrient Deficiencies Nitrogen. N is the most common deficiency of cannabis indoors or out. The first sign is a gradual, uniform yellowing of the large, lower leaves. Once the leaf yellows, necrotic tips and areas form as the leaves dry to a gold or rust color. Symptoms that accompany N deficiency include red stems and petioles, smaller leaves, slow growth, and a smaller, sparse profile.
Remedy by fertilizing with any soluble N fertilizer or with a complete fertilizer that is high in N. If your diagnosis is correct, some recovery should be visible in three or four days. New growth will be much more vigorous and new stems and petioles will have normal green color. Indoors, you should expect plants to need N fertilization a few times during growth. Once a plant shows a N deficiency, you should fertilize regularly to maintain healthy and vigorous growth.
