Can my leaves be hotter than the air temp under LED?

Blue brother

Well-Known Member
His findings might actually be accurate, but if they are then his plant is not transpiring properly like he’s allready figured out
 

Billy the Mountain

Well-Known Member
You people have the op not believing his own eyes. He’s ready to toss his thermometer cuz it won’t calibrate.
LST is hotter than ambient under any light—Hps, LED the sun —ANY LIGHT. Not sure if you people are ignorant or stubborn.
The water evaporates from the leaves and cools the ambient air.
You can repeat the same illiterate bullshit until you're blue in the face but it doesn't change the facts; you're demonstrably wrong.

Perhaps learn a little about evaporative cooling
 

bk78

Well-Known Member
You people have the op not believing his own eyes. He’s ready to toss his thermometer cuz it won’t calibrate.
LST is hotter than ambient under any light—Hps, LED the sun —ANY LIGHT. Not sure if you people are ignorant or stubborn.
The water evaporates from the leaves and cools the ambient air.
Smoking too much of that turd you posted earlier, homie.
 

PJ Diaz

Well-Known Member
I can’t believe these folks giving STUPID advice and OPINIONS.

Leaf temp is hotter than ambient —ALWAYS—with lights on. Go stand in the street barefoot when it’s 90 f outside and wonder why you get second degree burns.

You should aim for 84f ambient in your tent while running LEDs. LST (leaf surface temp) likes to be 86–88f with lights on. Do a little research on cannabis leaf surface temperatures running LEDs.
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LeastExpectedGrower

Well-Known Member
Science say no

Under LED lighting, LST is generally 2-3 °F LOWER than the ambient air temp. This is due to the transpiration of water which cools the leaf the same way sweating cools the skin.
Anytime I've checked mine (with full spectrum LED QBs), I'm right around 2f degrees cooler for LST with my Inkbird IR thermometer.
 

Bullmark

Well-Known Member
Wow….usually folks don’t respond well to my posts because I ramble on too long…..I’m stoked to see such a lively discussion.
I’m hoping it’s my thermometer b/c everything else in my grow space is dialed in pretty good.
I have the intake and exhaust in ideal positions w/ an exhaust fan that’s plenty powerful for my small space.
I have good air circulating below and above the plant canopy.
I have an Inkbird connected to a small heater and a humidifier…..the last 12 hr light cycle the air temps stayed between 74-76F and the RH between 46-50%.
My HLG 320 is running at about 80% intensity and is currently 20” above the canopy.
The PPFD is somewhere in the very moderate range for late flower.
Of course I measured the LST a dozen or more times today and about half the time it was almost exactly the same as the air temps…..but the other half it was reading 1 or 2 degrees ABOVE…..which I know is not supposed to be the case.
One of the two remaining Plants is in full senescence mode…the pics are from 3/4 days ago…...lots of purple along with a serious fade overall. To be honest she looks ready, but there are way too many sparkling clear trichs. This is one case where the physical appearance of the buds say it’s ripe but the trichs say otherwise. Usually it’s the other way around where growers see an abundance of milky trichs and wanna chop even though the buds are still short of ripe.
I’m gonna try my thermometer on a buddy’s plants…..they’re under a LED also, so maybe I can determine if this is all due to equipment error or if there really is a fly in my ointment.
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