# Leaf surface temperature



## next (Apr 3, 2015)

Hey guys

Has anyone out there checked the temperature of their canopy / leaves using an infrared temp gun? I'm curious in the difference of the leaf surface temperature between LED, and HID lighting, in relation to the ambient air temp.

Also does anyone out there know the "optimal" leaf surface temperature? The actual temperature of the plant itself? Not alot of information covering the subject. One source says that with HID lighting and an ambient air temp of 75, the leaf surface temperature is 85'. That to me, would mean that a leaf surface temperature of 85 is ideal, people have been using HID's for along time and this is the temperature they get the best results with. The temperature of the plant, effects the metabolic rate, which effects the rate of growth.. So to me this is a pretty important piece of information, and some data and input on the subject would be great.

I have an LED setup, and with my infrared gun I get a reading of 78degree's with an ambient air temperature of 79. My Led light has a few infrared diodes but still doesn't put out much radiant heat, when compared to HID lighting. So I get a  1degree temperature decrease of the leaf when compared to the ambient temp. Humidity also plays a role, the lower the humidity, the higher the rate of transpiration, and that leads to evaporation and cools the leaf. My RH is 43% Anyone else have a temp gun to post some results?

Thanks MP


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## Joe420Camel (Apr 3, 2015)

65F leaf temp gun
73F air temp probe @ canopy level
41% RH

didn't read post really 
sorry, bed time! 
just easy to add data
:48:


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## next (Apr 3, 2015)

What type of light u runnin, Joe?


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## Joe420Camel (Apr 3, 2015)

sorry
minor detail missed, I was too tired!! 

View attachment New Bitmap Image.jpg


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## next (Apr 3, 2015)

Interesting that you have a -8 degree difference, I think there are alot of factors involved, but nice to see, thankyou for posting!

Really hoping to get some numbers with people running HID's, i'm guessing they would have higher leaf temps compared to ambient temps.


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## echO (Apr 3, 2015)

Love my infared thermometer!


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## next (Apr 3, 2015)

Thankyou echO,

Mmm, anyone with some outdoor plants wanna get in on this? Curious to know the temperature with natural sun light as well


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## The3rdman (Aug 5, 2018)

When I place a thermometer at canopy level, it may read 85 degrees, but my infrared temperature gun will show 78 degrees on the canopy.  This leads me to suspect the plastic in the thermometer is absorbing and retaining the heat and is not accurate for temperature reading under the light.


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## Keef (Aug 5, 2018)

I run LEDs and in 5 years I have never measured leaf temp !-- Does the plant like what I'm doing or not ?- If not then change it !-- Fans move plenty air and I'm kinda puzzled by this whole concept !-- If the leaves are burning then move the light up off them some !-- If they digging it then leave them alone !


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