Heat stress

Leaves fold up like a taco and droop in the afternoon. Keep the canopy in 20–27 °C and act fast above 28–30 °C.

Symptoms

• Leaves fold up at the edges like a taco.
• Afternoon droop that recovers overnight.
• Dry or crispy tips, especially near the light.
• Slow, stretchy growth and loose, fluffy flowers in prolonged heat.

Quick checks

• Measure temperature at the top of the canopy, not the floor.
• Back-of-hand test: if it feels hot after 30 seconds at the top of the plant, the light is too close or bright.
• Check the solution temperature in hydro (under 24 °C).

How to fix it

1. 1
   Environment

   Free fixes first

   Run the light at night, draw intake air from the coolest place you can, vent outside the room and keep sun off the tent.

2. 2
   Environment

   Move more air

   Size the extractor up, keep ducting short and straight, put intake low and extraction high, and aim clip fans across the leaves.

3. 3
   Environment

   Dim or raise the light

   Losing a little light beats cooking the plant.

4. 4
   Feed

   Feed a little lighter and watch the roots

   The plant drinks more in heat so salts build up faster. Stay at the lower end of the chart and keep hydro solution at about 18–21 °C.

5. 5
   Support

   Support the plant

   Keep Stress in at the chart rate. Monkey Mist, sprayed when the tent is coolest in growth and early flower, can help the plant bounce back.

Likely causes

• Canopy above 27 °C, especially past 28–30 °C.
• Undersized extraction, long or kinked ducting, or recirculating hot air.
• Light too close or too bright for the temperature.
• Hot intake air in a UK summer; LED drivers or other kit inside the tent.

What to avoid

• Don't add CO2 in an extracted tent.
• Don't drown the plant to cool it: use the lift test.
• Don't put loose ice in a reservoir (sealed frozen bottles only, in an emergency).
• Don't spray maturing flowers.

Prevention

• Plan for summer: night running, a bigger extractor, LED over HPS.
• A max-min thermometer at canopy height.

Monkey products that can help

Stress

Monkey say silicon helps the plant manage abiotic stress such as heat. It can help, not cure.

2 ml per 10 L every week. Always add it to the water first and mix thoroughly before adding anything else.

View product →

Monkey Mist

Monkey say it helps plants bounce back from heat, drought or pest pressure. Spray in growth and early flower only, when the tent is coolest; never on maturing flowers.

Ready to use, no mixing. Mist evenly over the tops of the leaves in propagation, growth and early flower only. Safe with the lights on. Never spray maturing flowers.

View product →

Products support a healthy plant. They don't replace fixing the cause.

When to get help

If the canopy stays above 30 °C even with lights at night and full extraction, email info@monkeynutrients.co.uk for set-up advice.

Related problems