Wind burn is local damage on leaves that sit in a constant direct airflow. The leaves lose water faster than the roots can supply it, so they curl, claw, rattle or turn crispy, typically only on the side of the plant facing the fan. Airflow changes leaf temperature and transpiration (Nelson and Bugbee 2015); the term itself is Grower practice.
In practice
The giveaway is position: damage on one side, matching the fan, while the rest of the plant is fine. Angle fans to move air across and above the canopy so leaves flutter gently, use oscillating fans, and keep them off the colas.
Don't confuse with
- Heat stress: tacoing across the top of the canopy wherever it is hottest.
- Leaf clawing: tips hooked down across the plant, linked to nitrogen or water.
- Underwatering: the whole plant goes limp.
Leaf temperature is the actual surface temperature of a leaf, which often differs from air temperature by 1–3 °C depending on light source and transpiration.The evaporation of water from a plant, mainly through open stomata, which pulls water and dissolved nutrients up from the roots.An oscillating fan sweeps back and forth to circulate air over and through the canopy, mixing the room and preventing still, humid pockets.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.Heat stress is damage or slowed growth when leaf or canopy temperature rises above what the plant can handle, typically above about 30–32 °C (86–90 °F) in cannabis.A leaf whose edges fold upward along the midrib like a taco shell or canoe, usually at the top of the canopy; a sign of heat, high VPD or excess light.Leaves whose tips hook sharply downward like a claw, usually on dark green leaves; a classic sign of excess nitrogen, and also seen with waterlogged roots.Underwatering is letting the medium dry too far between waterings, so the plant loses turgor and wilts, with limp, papery leaves and crisping edges if repeated.Airflow is the movement of air through and around the canopy; it thins the still boundary layer on leaves, evens out temperature and humidity, and lowers mould risk.Vapour pressure deficit: how much more water vapour the air could hold at its temperature, in kPa; it is the main environmental driver of transpiration.
