Brown Spots on Cannabis Leaves? (Rule Out These Causes)
Brown spots can come from calcium issues, splash burn, pathogens, or pH drift. Don’t assume one cause — confirm with context.
Brown spots on cannabis leaves? See top causes (Ca, pH drift, splash burn, pathogen) and analyze your plant in seconds.
Common Causes
- Calcium deficiency (common in coco/RO)
- pH swings causing lockout
- Foliar splash burn from nutrients
- Early pathogen/leaf septoria in humid rooms
How to Tell Which One You Have
Note location (new vs old leaves), pattern (spots vs edges), and environment (humidity, foliar sprays).
FAQ
Is this cal-mag?
Often yes if in coco/RO. Check pH and VPD before dosing.
Could it be fungus?
If spots spread with yellow halos in high humidity, consider pathogen and improve airflow.
Did I burn with foliar feed?
Random splatter-like spots after spraying often mean foliar burn.