What it is
Stress from high temperature. Above 28-30 °C the plant loses water faster than the root can supply it, photosynthesis slows down and it gets stressed.
How to tell
The upper leaves fold up at the edges, like a taco or a canoe, to expose less surface to the heat. Dry spots can appear. In flowering, the buds come out loose and airy, and sometimes new "towers" of flowers grow on top (foxtailing). Aroma is lost: terpenes evaporate in the heat.
What to do
Pull out the hot air (exhaust fan), move the air (fan), raise the lamp, run the light at night, when it is cooler, or use an air conditioner. In the heat the plant drinks more: don't let it run short of water.
Good to know
Indoors, lamps are the main source of heat, and it shows more in a small spot. LED runs cooler than old sodium lamps, but it still heats up.
🎮 Practice it in UnderGrow
Above 30 °C the plant gets stressed. Indoors it doesn't go over 33 °C (the damaging 35 °C only shows up outdoors). Heat also helps spider mite, whitefly and light burn. You lower it with the exhaust fan or the air conditioner (tap equipment › on the panel).
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