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VPD question...

M

mrlucky405

Member
All the charts etc talk about air temp and RH as an inputs. However, It's not specified if those are general air and RH readings in the room or if those are taken at canopy level. I'm assuming canopy level is the way to go, because that's where the plants are experiencing the environment, not at some random spot inside the room. Thanks for your time!
 
R

RockinRobot

Active member
I believe the charts go by Leaf temperature. Can be measured with infrared thermometer.

Your Rh should be fairly stable if you have adequate fan circulation in the room.
 
I'mback

I'mback

Comfortably numb!
mrlucky405 said:
All the charts etc talk about air temp and RH as an inputs. However, It's not specified if those are general air and RH readings in the room or if those are taken at canopy level. I'm assuming canopy level is the way to go, because that's where the plants are experiencing the environment, not at some random spot inside the room. Thanks for your time!
Click to expand...
Your environment, is your environment. Stop over thinking it!
 
ion

ion

Active member
good question relative to PM issues i think......i have a plant im watching that has pm developing couple inches up from soil on stems coming from the main, woody chunk, the leaves show no sign. vpd is pretty much synonymous with pm methinks? if your enviro is dialed in goodly but yer still getting pm its vpd......not big cakes of the shit, tiny patches here there.

running tents with 3-4 fans per running low, full circ but not blowing hard as that can increase vpd........mrlucky, i see what yer saying and have experienced pm mostly upper half of canopy, but i wager thats strain dependent?
 
R

RockinRobot

Active member
ion said:
good question relative to PM issues i think......i have a plant im watching that has pm developing couple inches up from soil on stems coming from the main, woody chunk, the leaves show no sign. vpd is pretty much synonymous with pm methinks? if your enviro is dialed in goodly but yer still getting pm its vpd......not big cakes of the shit, tiny patches here there.

running tents with 3-4 fans per running low, full circ but not blowing hard as that can increase vpd........mrlucky, i see what yer saying and have experienced pm mostly upper half of canopy, but i wager thats strain dependent?
Click to expand...

PM is more related to too high of humidity, especially during lights out, and/or not enough airflow, than to actual VPD. PM and other molds like dark, cool and damp. I always have to run dehumidifier during lights off.

If you are only seeing it lower down perhaps not enough airflow under the canopy but I would monitor night time humidity levels.
 
zeke99

zeke99

Active member
I'mback said:
Your environment, is your environment. Stop over thinking it!
Click to expand...

I mean, not really.

The temperature at leaf surfaces is going to differ from the temperature above the light source, near the floor under the plant, behind the plant, etc.

You could see differences of as much as 10-20 degrees Fahrenheit.


edit: I'm talking about HIDs, not LEDs. I've no experience with LEDs.
 
Last edited:
I'mback

I'mback

Comfortably numb!
If you have things dialed in, to include but not limited to "appropriate" exhaust. One should not see that large a fluctuation (up to 20 deg F) in their tents. I'm using LEDs. Granted the warmest/humid air will be found at the ceiling.
 
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