Causes of leaf curling

You forgot to sacrifce a chicken.

​1. Temperature Stress and Heat ​The Cause: When ambient temperatures get too high (typically above 85°F or 29°C), or if lights are placed too close to the canopy, leaves will often cup or canoe upward to reduce surface area exposed to the heat. ​The Look: Edges curl upward, resembling a taco shell or spoon. ​2. Nitrogen Toxicity ​The Cause: An excess of nitrogen—often from heavy feeding during the vegetative stage or an overly "hot" soil mix—causes rapid, abnormal cell growth. ​The Look: Leaves turn a very dark, glossy green. The tips curve downward sharply, creating a distinct "claw" shape (often called "the claw"). ​3. Overwatering or Underwatering ​The Cause: ​Overwatering: Roots suffocate in waterlogged soil, depriving them of oxygen. This leads to drooping and a heavy, downward curl of the entire leaf. ​Underwatering: Severely dry roots can cause leaves to curl downward or downward-droop as the plant conserves moisture. ​The Look: Leaves feel heavy and limp. With overwatering, the medium stays wet for days; with underwatering, the soil pulls away from the edges of the pot. ​4. Root Zone Issues & pH Imbalance ​The Cause: If the root pH drifts out of the optimal range (6.0–7.0 in soil, 5.5–6.5 in coco/hydro), the plant cannot properly uptake nutrients, leading to lockout, nutrient burn, and subsequent leaf distortion or curling. ​The Look: Often accompanied by yellowing, tip burn, or necrosis (spots) on the leaves. ​5. Wind Burn and Low Humidity ​The Cause: Direct, high-velocity airflow from oscillating fans or excessively dry air can shock the foliage. ​The Look: Leaves curl or twist inward/downward on one side of the plant closest to the fan.

Up or down?

Curling up/taccoing is to much light.