How hot is too hot?

Discussion in 'Growing Marijuana Indoors' started by ohraesisstrakur, May 23, 2010.

  1. So I've heard many varying things both on this forum and in books on the subject.
    Some people think 80f is hot. The Cannabis Grow Bible says heat stress begins near 85f and that 75f is the optimum temperature, while I've also heard 84-86f is the optimum temp and plants can tolerate up to 90f fine. What are your opinions on the subject? How hot is too hot?
  2. 35 views and no one has an opinion?
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  3. Depends on the strain I say. I'd assume sativa's take better to heat than indica.
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  4. I got 2 indicas and 1 sativa, My sativa is thriving with temp ranging from 78-95, One of the indicas is doing really well as well. The other one is having growth problems that may be attributed to heat stress or some sort of nute problem. I feel like plants can handle the high heat with other conditions being optimal ie Humidity, Nutes, pH. I feel like plants can handle the heat, especially since the can handle growing in outdoor environments such as India and the Middle East, which are just as hot.
  5. Yeah I agree that it could be very strain depent. It was just baffling me that someone would say 80 or even 85 was too hot. These plants are native to India, Pakistan, Afghanistan, and so on. I know for a fact it gets a hell of alot hotter than 85 in those places. I also know I've grown outdoors thru 95f+ summers. Still if I see a 95 on my thermometer in my closet I might have a mini panic attack.
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  6. #6 Sam87, May 24, 2010
    Last edited by a moderator: May 24, 2010
    Depends on the genetics. But generally, you want to stay below 85f to keep your buds nice and dense.

    They can tolerate pretty much whatever on a short term basis. I had my fan go out once, box temp at 107, and they were happy as can be. But, if you're running Indica or Hybrid genetics, and are not running CO2, then around 75 is ideal. I shoot for 72, seems to be what my plants like best. But if you have to run at 80, it's not a big deal.

    Also, outdoor plants are a bit different from indoor plants. They harden off quickly, and in ground their roots maintain a relatively stable temp. You have to remember that in containers, you're heating up that entire plant, and everything it takes in.
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  7. That's true Sam, but I was growing in containers outside, they still made it just fine.
  8. A Cannabis plant will make it pretty much anywhere, definitely nicknamed weed for a reason. It's the matter of fine tuning for yields and quality that's such a bitch. But all in all, people put waaayyy too much work into their plants. Don't get me wrong, attention to detail is very important, but the way some people treat the subject, you'd think that the damned things wouldn't even make it past a seedling in nature.

    The bitch part of everything to do with growing, is that there is no set model for perfection. You need to get everything dialed in with the genetics that you have, not with what Cervantes or Rosenthal or Green has, you know? If the plant works for you, then it works for you. But you can always play with it to see if you can make it work better.
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  9. Due to unchangeable circumstances, my grow tent is at 100 degrees when the light is on. Although the yield is smaller, I can still grow.

    85 is too hot IMO
  10. Well what about plants outside that grow in 100+ temperature sometimes.
  11. They don't yield as well as in a controlled enviroment. Or, they have/are adapting to their enviroment. Same as anything else with plants, you have an optimum range, and a tolerated range, which can both differ by way of genetics and other enviromental factors.
  12. Both indicas and sativas can tolerate indoor temps into the high 90's if they are well watered and cared for. I regularly get temps in that range and still have good yields.
  13. My grow room normally sits around 100f or tad more but have had nice yields! my last grow was same as I'm doing 2 AK47 x Lowryder 2 (auto) and got just over 2 and half o'z dried per plant :)
  14. So I have 5 seedlings auto cheese strain my closet. Which is kinda small 2ft by 3ft. I have a hydro bin with 2 plants. 2 in four gallon pots and 1 in a two gallon pot. I started the biggest three 10 days ago. One a week ago n the one should sprout any day. Will this be a problem when I have to switch to 12/12 since the others are 10 days behind..... The reason I ended up here on this thread is my closet high hemp been 85° with avg of 81° that's fine right....

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  15. Buddy, if youve got auto's you dont need to switch to 12/12. It will stay on 18 hours until they finish.
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  16. I thought once there ready to bud you still have to switch 12/12. Your right tho I just looked it up... I thought plants need darkness for photosynthesis. Not sure what exactly happens during that process. So I been doing 24hrs of light.. So auto flowers the light can be on for there whole 3 months?
  17. Yup, you don't have to do 24 hours if you want to set it up so during the hottest 6 hours of the day you have lights out. Most people do 18/6 and myself I do 19/5.
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  18. Yea I'm probably gonna have to do that soon its not even that hot outside and my closet is at 85° I can only imagine what it will be if there is a heat wave. I use window ac units for the house but my closet doesent get fresh air will , this be a problem.. I have the hps cooltube vented thru the attic but theres nothing bringing fresh air in just the exhaust fan sucking the heat from the light out.. I could cut another hole in the attic and get another exhaust fan to blow air in but its gonna just be hot air from the attic..

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