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heat stress during flowering

Heat stress during flowering
Important for Hydroponic Growers! High temps can trigger root rot, a serious problem that can kill your plants.
If flowering cannabis plants are grown under too-hot conditions for a long time, sometimes they respond by growing new buds on top of the old ones. When you see extensive growth on top of the buds closest to the grow lights, that’s a sign that the grow light is too close or the temperature is too high. Some people call the new growth (which often grows in spires) “fox tails.”
Heat stress is even more damaging in the flowering stage since plant is no longer growing many new leaves. Indica-leaning strains are most prone to heat damage in the flowering stage. Heat damage during budding will reduce your yields by demolishing many of your most important leaves, while also causing buds to grow airy with ugly foxtails.
When the heat gets too high, the edges of the serrated leaves will begin to curl up even if there are no burns or other signs of light stress.
Some things to try when you know the weather outside is going to be hot or dry:

  • water plants in the evening or early morning to help prevent water evaporation during the hottest hours
  • keep roots cool – for example by putting your potted plant in a ceramic pot to help insulate the roots from the sun. I’ve also heard of growers digging a hole in the ground to place their potted plant inside, because the ground is usually cooler than the air when the temperature gets high
  • kelp extract for roots – provide a small amount of liquid fertilizer that contains seaweed kelp extract (can help protect against heat stress)
  • increase shade to reduce the heat experienced by plants – you can use an old sheet or other cloth as a short term solution, or get a profesionally made “Sun Shade Sail” which is made particularly to create shade outdoors. It’s important to remember that giving plants shade for more than a few days will make them less “hardened” to the sun, and you may need to reintroduce full sunlight back slowly to prevent them from getting shocked from the light intensity
  • move potted plants – luckily with potted plants, it’s usually easier to move them out of direct sunlight during a heat wave
  • take extra good care of heat-stressed plants – when cannabis plants appear heat-stressed, try to baby them as best you can, and offer shade during the hottest days.

Cannabis will also display heat stress when grown outdoors in hot, dry weather, especially when not given enough water.
Solution: Get a way to monitor temperature. Control heat by whatever means necessary using the steps outlined below.
You may consider removing grow lights further away from the tops of the plants if heat is a problem.
Too hot for your cannabis in the grow room? Learn how to save your plants from heat stress with a variety of techniques as well as certain supplements!