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What Range Should I Maintain For My Growroom Humidity & Temperature?

straightup

New Member
You don't want a sudden drop of 20 degrees. The perfect Temp is 77 F. Anywhere between 75 - 82 & you are good with Lights on. I'm told 68 F is the lowest Temp you want to go (lights off) & 84 F is the max (lights on / without Co2). If using Co2 then 84 - 94 F are the Temps you want.
Don't mean to be rude but don't the temps depend on what kind of lighting you are using? When someone is using LED, they don't heat up the leaf surface temperature as much as HID given you have more control of the spectrum. Optimal leaf surface temperature for an LED grow should be at least 9 F higher than an HID grow.

"When growing under optimized-spectrum LED plant lights, the lack of excess infrared and other unusable light causing the leaves to heat up means that ambient air temperature needs to be warmer than for the same plant grown under any light (natural or artificial) which is not optimized for plant growth." LED Grow Lights | Growing Kits & Indoor Commercial Grow Lights
 

Buds Buddy

Grow Journal of the Month: May 2020
The leaf temperature would be controlled by how high you hang your light. Closer it is the warmer your leaf temp. As far as the grow area being heated warmer .... never heard that before. Just a low temp of 68 F lights out & a high of 84 lights on to be in a good growing range with 77 F being the target temp. Been shooting for 77 F for 3 years now with MH, HPS, Fluorescent, Bluple LED & White LED. Tried all these lights & always went for 77 F.
That light company is the only one I've ever heard make that statement even. They are some top of the line lights. Maybe they know something other light companies don't.
Either way, I'll stick to the 77 F that I know works well.
 

AdaminCO

Well-Known Member
Take a peep at what I found today.
You do have to take in count lights that have IR and UV.

 

straightup

New Member
The leaf temperature would be controlled by how high you hang your light. Closer it is the warmer your leaf temp. As far as the grow area being heated warmer .... never heard that before. Just a low temp of 68 F lights out & a high of 84 lights on to be in a good growing range with 77 F being the target temp. Been shooting for 77 F for 3 years now with MH, HPS, Fluorescent, Bluple LED & White LED. Tried all these lights & always went for 77 F.
That light company is the only one I've ever heard make that statement even. They are some top of the line lights. Maybe they know something other light companies don't.
Either way, I'll stick to the 77 F that I know works well.
The link at the end of the post that I quoted has an abstract that shows the results of their tests on several different plant types, including cannabis, using a FLIR gun. Obviously it's impossible to know how controlled their experiments actually were, but I'm not seeing any issues in what their premise states - which is that full spectrum LEDs do not produce excess infrared nor any other unusable light that HPS and MH lamps do, meaning the leaf is not being subject to the heat that the aforementioned light systems (HPS MH) produce. If we agree that the leaf's optimal surface temperature is ~86F for various metabolic reactions to occur, then it is necessary to raise the ambient temperatures approx. 9 F to make up for the LED's more efficient use of the light spectrum.

77F ambient in a HPS grow should be damn near optimal for LST. But if you are running LED's, you will need to raise your ambient temps to somewhere around 84 - 86 F.

I encourage you to take a look at the paper I linked and if nothing else check out the graphs they made comparing the surface temps of various lighting setups.
 

CannaFish

Well-Known Member
warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower? Specifically what temps will produce maximum thc and preserve the terpenes? I've read somebody on here talk about not going over 80 degrees F, but I'd like to learn some more specifics about getting the most out of the available terpenes. I have a Haze that smells different depending who and where it's grown.

check out this article...

"It's also easier to control factors like temperature and humidity in these smaller environments. RB-26 maintains a lower overall temperature than most growers—72 to 77 degrees as opposed to high 70s or low 80s. "Heat is one of the biggest stressors of plants and as your temperature rises, you're going to be degrading terpenes [aromatic plant compounds] and oil production, and that directly affects potency,""
 

CannaFish

Well-Known Member
Here is my take. I keep my room at 68-72 degrees and humidity at 55%. I do this cheaply. Here is how. I have a lot of ac/heat knowledge, was in that business at one time. You get on your Facebook market , Craig’s list , garage sales. People are always getting rid of humidifiers and dehumidifiers that have settings. Usually they heat the air mist or dry heat. You set the dehumidifier at 55 and the humidifier at 60. For temp control, you might have to find someone to do this if you don’t know how. Get one of those hotel combo heat and air units. A 110 volt thermostat. Wire it where it has a range of 5-7 , do that so it does not constant run on heat or ac fighting itself .set it at 70. Get yourself a 6 inch inline with filter and stat on it. Remember that air in your house has a higher CO2 than outside air. I don’t use CO2. I find it a waste. I am cheap, like to save money. Been at this since the 70’s in Newton County Arkansas. For those of you young guys that use to be known as the place to get the best for a long time. I won’t get into much of that. I am here to soak in what others know and learn, and to share my own experience. Appreciate feedback. I also now use led, use about 4500 watts in 50 sq ft space.
excellent info. thanks for sharing your knowledge.
 

AdaminCO

Well-Known Member
warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower? Specifically what temps will produce maximum thc and preserve the terpenes? I've read somebody on here talk about not going over 80 degrees F, but I'd like to learn some more specifics about getting the most out of the available terpenes. I have a Haze that smells different depending who and where it's grown.

check out this article...

"It's also easier to control factors like temperature and humidity in these smaller environments. RB-26 maintains a lower overall temperature than most growers—72 to 77 degrees as opposed to high 70s or low 80s. "Heat is one of the biggest stressors of plants and as your temperature rises, you're going to be degrading terpenes [aromatic plant compounds] and oil production, and that directly affects potency,""
D3571296-7BA7-416D-BE6C-55DDC000FF51.jpeg

RH is just as important as temp. These are two charts I use for reference.

75 degree leaf temp is optimal.
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower?
It depends somewhat on strain choice, of course - as "cannabis" isn't a single, generic object like (for example) pure water is. But it also depends on the amount of light-energy the plant is receiving and the CO2 level. Therefore, there is no simple answer. That 88.6°F (IIRC) temperature that gets mentioned occasionally assumes normal ambient CO2 level and the maximum light-energy that the plant is capable of processing under that atmospheric condition. Again, somewhat strain-dependent.

Also, various factors may influence the maximum temperature that a cannabis plant can tolerate. A cannabis plant being grown in a large DWC reservoir that is very highly (and constantly) oxygenated, and that has a more or less constant high flow of fresh air to aid/facilitate transpiration will generally be capable of tolerating significantly higher temperatures - and will likely continue to thrive even when an identical plant placed in the ground outdoors in similar temperatures would experience periods when there is "not much going on" in terms of development. But even that outdoor in-ground plant will tolerate higher temperatures if it has a good root system that allows it access to adequate moisture and, again, is able to maintain a high rate of transpiration. Among other things that transpiration does is to enable a plant to self-cool.
 

straightup

New Member
D3571296-7BA7-416D-BE6C-55DDC000FF51.jpeg

RH is just as important as temp. These are two charts I use for reference.

75 degree leaf temp is optimal.
While there are some fluctuations to optimal LST, depending on strain, there was a university study conducted a couple years ago on optimal LST for cannabis. The conclusion was that 25 - 35 C was considered optimal for photosynthesis to occur. That would be 77 to 95 F. I've seen other more informal studies that have narrowed that number down to somewhere around 85-86 F as being optimal for LST. This is assuming that your humidity is 65-75%.
 

AdaminCO

Well-Known Member
I found a very good study, but they deleted the link.
It all depends on your type of lighting. Ambient differs light to light. (Spectrum)
 

CannaFish

Well-Known Member
I found a very good study, but they deleted the link.
It all depends on your type of lighting. Ambient differs light to light. (Spectrum)
I did see a thread on icm that showed similar photos to the one you posted but it was LED vs HPS . It clearly showed the hps plant had higher LST than the LED plant at the same ambient temps.

I researched a little more about that grower RB26 I posted the link about above. Some one asked for some grow tips, he responded...

“ I'd follow the VPD chart for atmospheric conditions if you are new to growing. A simple Google search will bring up the image for you.

I use 1000W Gavita E-Series fixtures in commercial voltage - so the electrical draw will be different than what you're using. I believe the the 240V Gavita's pull 4.5A at 1000W.

I utilize coco in a drain to waste, multifeed application.

My plants are always topped, at least 2 times. Generally each plant is paired with a 54" tomato cage but these days I've been experimenting more and more with trellising with great results.

I've experimented with all the bottled nutrients from the hydro store and had best results with a mixture of Botanicare and with a couple Advanced Nutrients flowering additives. This past year I've been using raw agricultural salts and making my own nutrients however. This has gotten the cost down to about $.02/gallon.

There are lots of products that can help promote healthy plants. I'd look into silica additives and beneficial enzymes. Be wary of what you find off the shelf at hydro stores though - many of those products are just designed to take your money.

Happy Growing!”
 

straightup

New Member
I did see a thread on icm that showed similar photos to the one you posted but it was LED vs HPS . It clearly showed the hps plant had higher LST than the LED plant at the same ambient temps.

I researched a little more about that grower RB26 I posted the link about above. Some one asked for some grow tips, he responded...

“ I'd follow the VPD chart for atmospheric conditions if you are new to growing. A simple Google search will bring up the image for you.

I use 1000W Gavita E-Series fixtures in commercial voltage - so the electrical draw will be different than what you're using. I believe the the 240V Gavita's pull 4.5A at 1000W.

I utilize coco in a drain to waste, multifeed application.

My plants are always topped, at least 2 times. Generally each plant is paired with a 54" tomato cage but these days I've been experimenting more and more with trellising with great results.

I've experimented with all the bottled nutrients from the hydro store and had best results with a mixture of Botanicare and with a couple Advanced Nutrients flowering additives. This past year I've been using raw agricultural salts and making my own nutrients however. This has gotten the cost down to about $.02/gallon.

There are lots of products that can help promote healthy plants. I'd look into silica additives and beneficial enzymes. Be wary of what you find off the shelf at hydro stores though - many of those products are just designed to take your money.

Happy Growing!”
Hello CannaFish,

Here's the link to the study that was conducted by Black Dog about LST. If you don't want to read it - just check out the graphs they posted.

HPS vs LED Leaf Temp
 
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