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Help! My cannabis flowers are turning brown - is this mold?

Help! My cannabis flowers are turning brown – is this mold?

Getting the right answers in your cannabis journey can be tricky. But with The Cannigma’s Ask the Expert, you can find questions from readers like you, answered by a cannabis specialist. 

Question: Parts of my flowers are turning brown while the rest of the flowers remain green. The plants have been flowering for about a month. Is this normal? Can these brown flowers be used or should they be discarded?


Unfortunately,  brown flowers are not a normal part of cannabis growth and development, apart from when the plants are reaching their maturity. However it sounds like your plants are a lot younger than that. 

The most common causes of flowers turning brown are pests and pathogens that take hold in your crop. You are most likely experiencing Botrytis, otherwise known as gray mold, which is one of the most common pathogens – not only in cannabis but also in many food crops as well. Botrytis can infect any part of a plant, but in cannabis, it usually takes hold within the buds because it prefers dark and moist environments.

Humidity, moistness, and lack of ventilation are most likely culprits here. Once established, Botrytis spreads rapidly so you must act fast to save your buds. Using fungicides to treat Botrytis is not recommended as they won’t work fast enough to kill the fungus which, over time, has developed some resistance to chemical sprays due to overuse in the agriculture industry. The best thing to do upon identifying an infection is to closely inspect your plants and immediately cut off and discard any infected areas. 

Professional growers strive to prevent Botrytis from occurring in the first place. Every piece of equipment, large or small, is sterilized with a fungicide or bleach solution before it enters the grow room to kill off any fungal spores that may initiate an infection. In addition, they maintain proper humidity levels and air circulation in the growing environment at all times. 

Other reasons for flowers turning brown include nutrient deficiencies, and excessive heat coming from your light source. These are also related to the growing environment you are providing for your plants, so I would recommend checking your fertilizer and watering regime, as well as the distance between your lights and the plant. 

Since we can’t be completely sure about the exact cause, I would err on the side of caution and discard all the brown bits of your cannabis flower. I would also keep a close eye on the remaining flowers on a daily basis to quickly identify and remove potentially infected buds.

Remember, you will be harvesting first-class buds in no time at all if you keep making small improvements in your cultivation skills and knowledge with each crop that you grow, and as unfortunate as it is to see brown flowers, you can take comfort in knowing that every grower will experience this at some point.

Gianni Del Rosario-Makridis
Scientific advisor, The Cannigma
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