Sudden leaf drop over a day or two
Many leaves at once after a shock: cold, heat, spray, root loss or a pH crash..
- Also called
- leaves falling off suddenly
- plant dropping leaves
- leaves shed overnight
Likely causes, most likely first
Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.
Less likelyCold stress
Fix: Keep days at 22-28 °C (72-82 °F) and nights no more than 3-6 °C (5-10 °F) cooler and above ~15 °C (59 °F); warm the root zone. Cold-for-colour is real in purple cultivars, but claims of more terpenes or resin are unsupported.
Recovery: Growth resumes within a week; new leaves come in green.
How to confirm it
- Check temperature and RH at canopy height with a calibrated sensor. Put a calibrated sensor (salt test: a sealed bag with damp table salt reads 75% RH after 8-12 hours) at canopy height, out of direct light, and log for 24 hours including lights-off. Look for lights-off RH spikes and dew point.
Look for
Dropped leaves on the medium, and the leaves still attached..
The full guide: Why is my cannabis turning yellow? The master yellowing decision tree
Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
