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flower at 91 degrees no sign heat stress... am I crazy

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OG Tree Grower

Don't worry about leaf temp. It's always gonna be cooler than canopy temp or else your plant has stopped transpiring and is now dead. Canopy temp is important not leaf temp

Root zone temp is pretty advanced stuff to worry about, hydro res temps will often require a chiller but that's res temp not root zone temp. Depending on your system (mainly hp/lp areo,not or tables of whatever kind) you can slightly adjust "root zone temp" by pump duration and insulating your table/bucket ect
 
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Huckster79

Makes sense on leaf temp and with everyone using canopy temp- leaf temp is likely relative to that of canopy temp... Just simpler to measure canopy temp so that's what the community has built its guidelines off

Yea I wasn't thinking of trying to cool root zone but heard that's a limiting factor in our room temp that our girls cud handle higher temps of root zone was cooler... Didn't know if anything to it but sounded beyond reasonable control in promix! Lol
 
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MileHighGlass

Senior Member
Root zone temp is very important. With large notill pots like I use it's a lot easier to control. In hydro I would have no idea where to begin.

I have always used leaf surface temp as it varies from plant to plant, and area to area. So I have tried to keep that as even as possible. My room temp can be 74, but leaf surface temp can be 82.

It's just how I've always done it. Makes way more sense to me then an arbitrary number that is 1 or 2 feet away from your plant.

FYI a thermometer under a light will not give an accurate reading. You have to shade it.
 
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Ollie

Well-known member
Veteran
You might also get a volatile compound loss (Terpenes, Flavonoids) by running high temps.

We need more studies on this in practical, but less heat is in general a good rule to follow for maximum preservation of such.
 
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OG Tree Grower

It's not really relative tho. Leaf temp never goes above 85 that I've measured. They just transpire more water to keep that temp as room temps get higher. I have 7 thermometers in any given flower room. Most hung right at the canopy literally touching the leafs not 2 feet away.
 
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MileHighGlass

Senior Member
OG Tree Grower said:
It's not really relative tho. Leaf temp never goes above 85 that I've measured. They just transpire more water to keep that temp as room temps get higher. I have 7 thermometers in any given flower room. Most hung right at the canopy literally touching the leafs not 2 feet away.
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If it's under a light it won't read correctly. It has to be shaded. there are so many variables when taking readings that most people don't take accurate readings.

I will say I love the fact that you have 7 thermometers. More people need to do that. That is a great thing.

The reason I use the infrared thermometers is it is the most accurate reading you can get for a reasonable price.

Leaf surface temp under a 1000 watt light can be way higher than room temp. I only use 600 watt lights and I usually see 5-10 degree higher reading.

Got any pics of how you place your thermometers? I am interested as it seems you have thoroughly thought that part through. Maybe something for me to learn from such pictures.

Thanks for the dialogue.
 
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OG Tree Grower

I think your mistaken. Leaf temp is never above air temp.

I grow vertical so I just tie thermometers to the same strings I hold buds up with

2 above canopy, 3 at canopy 2 below canopy. Just look close beat the lights , some analog some digital and 2 heat guns.

I'm a petro engineer by trade, heat guns don't need to be in the shade, your measuring air temp between what u want and the gun, just hold the gun closer to the object
 

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MileHighGlass

Senior Member
OG Tree Grower said:
I think your mistaken. Leaf temp is never above air temp.

I grow vertical so I just tie thermometers to the same strings I hold buds up with

2 above canopy, 3 at canopy 2 below canopy. Just look close beat the lights , some analog some digital and 2 heat guns.

I'm a petro engineer by trade, heat guns don't need to be in the shade, your measuring air temp between what u want and the gun, just hold the gun closer to the object
Click to expand...

Wasn't talking about heat guns being in the shade. Was talking about a standard themroter like most people use.

My leaf temp is always above air temp. How can I mistake this?

A leaf in full sunlight will be absorbing energy thus be at a higher temp than air temp.

I don't know what being a petro engineer has do with anything, but that is a great achievement none the less.

Thanks for the pics. I like the vert setup. I ran vert 5 years ago, and it was a great learning experience.
 
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MileHighGlass

Senior Member
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MileHighGlass

Senior Member
OG Tree Grower said:
I think your mistaken. Leaf temp is never above air temp.

I grow vertical so I just tie thermometers to the same strings I hold buds up with

2 above canopy, 3 at canopy 2 below canopy. Just look close beat the lights , some analog some digital and 2 heat guns.

I'm a petro engineer by trade, heat guns don't need to be in the shade, your measuring air temp between what u want and the gun, just hold the gun closer to the object
Click to expand...

Air Temp 71.4 Leaf temp 73 with lights turned down to 50%. If I turn them up to 100% the leaf temp will increase 5-8 degrees, and the air temp will increase 3-5 degrees.
 
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OG Tree Grower

Thank you, I thought u were talking about the heat gun that's why I said what I do for a living, I use heat guns literally 100 times a day, stoned and thought it was relevant

It's not possible to have higher leaf temps than air temp.

I'm really not trying to sound like a dick here but man.... Plants transpire water through the leafs to keep cool, same as grass , trees or any other plant that I'm aware of. It's not opinion and I didn't just make this up. This is very basic growing knowledge , it goes hand in hand with growth rates and vpd. That's why when your humudity is to lo the plant uses most of its energy through transpiration to keep the leaves cooler than the air.
 
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OG Tree Grower

Calibrate your heat gun?
 

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MileHighGlass

Senior Member
I just did a tree outside and the leaf temp in full sun was 91.6 and the air temperature is 79.

My gun is not off that much. I did just do the wall in my house with an air temp of 74 and it was 74.1

AM interested in calibrating my gun though.
 
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OG Tree Grower

MileHighGlass said:
So whats the best way to calibrate the gun?
Click to expand...

There all different, user manual will have directions but honestly I just reference it with 2 other thermometers.
I dunno what to say man. I gave you all the right info. I don't say crap that's not true so u have something weird going on with your gun or leaves. Dunno but I have never ever saw a plant that didn't cool down through transperation. Maybe a cactus lol
 
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MileHighGlass

Senior Member
OG Tree Grower said:
There all different, user manual will have directions but honestly I just reference it with 2 other thermometers.
I dunno what to say man. I gave you all the right info. I don't say crap that's not true so u have something weird going on with your gun or leaves. Dunno but I have never ever saw a plant that didn't cool down through transperation. Maybe a cactus lol
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Do you have the ability to go outside and take a reading of a leaf temperature in full sun with your gun?

I would be interested to see what it is.
 
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OG Tree Grower

Yes I just did with two different heat guns before u even asked.Same as always, 7-6 deg cooler than the air. I can do it again and take a pict if you absolutely Need it.
 
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MileHighGlass

Senior Member
OG Tree Grower said:
Yes I just did with two different heat guns before u even asked.Same as always, 7-6 deg cooler than the air. I can do it again and take a pict if you absolutely Need it.
Click to expand...

Whats your humidity like outside? I am trying to figure what the difference is. This is more than interesting.
 
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