VPD charts

[Brian420pm]

Vapor Pressure Deficit (VPD) provides ideal temp/humidity pairs to maximize the health of your plants. In other words, if the temp goes up then humidity should also increase to maintain a better balance.

Once you settle on one Vapor Pressure Deficit (VPD) chart (yah many to choose from), then you pick the temp/humidity range you want. You'll get the hang of it after a few grows. I simplified and printed one chart and it's always handy for reference.

Temp RH
73 52
74 53
75 54
76 55
77 57
78 59
79 60
80 61
81 62
82 65
83 66
84 66
85 67​

The science behind this is fascinating! It's all about what's happening within the millimeter of space above each leaf. There are ideal ranges depending on the difference between ambient humidity and leaf surface humidity! Fans blowing directly on your plants from above will measure a max humidity difference, while still air shows little to none.

Using any of the general charts will give you acceptable results, but more detail is out there, I encourage exploration!

 

[Enr0n]

I have been using VPD to monitor my ladies and find it very beneficial. Like you said there are many charts. Do you keep your temp/rh meter at the top of the plant or at the base of the plant near the container? I keep mine at the base of the container. I like it because it shows the various stages of growth and gives me a target temp/rh.

 

[oldsmokey]

I believe the charts are based on leaf temp not room temp.

 

[Brian420pm]

This is a good one as well. I measured my leaf surface temp with a IR temp gun, they are 1 degree cooler than other areas of the tent. dimluxlighting.com has all the charts based on that difference.

 

[Brian420pm]

I believe the charts are based on leaf temp not room temp.

The difference between the two, actually.

 

[oldsmokey]

Just bookmarked that site for later thanks Brian!

 

[Enr0n]

I believe the charts are based on leaf temp not room temp.

OK well I have been monitoring the lower part of the plant right near the soil. The way I saw it the chart is based on the temp/rh of the growth medium, so the chart is referring to the difference in "base" ph in the soil with the VPD chart showing the difference +/- from the base ph reflecting the current temp/ph.

 

[Dadbod]

Vapor Pressure Deficit (VPD) provides ideal temp/humidity pairs to maximize the health of your plants. In other words, if the temp goes up then humidity should also increase to maintain a better balance.

Once you settle on one Vapor Pressure Deficit (VPD) chart (yah many to choose from), then you pick the temp/humidity range you want. You'll get the hang of it after a few grows. I simplified and printed one chart and it's always handy for reference.

Temp RH
73 52
74 53
75 54
76 55
77 57
78 59
79 60
80 61
81 62
82 65
83 66
84 66
85 67​

The science behind this is fascinating! It's all about what's happening within the millimeter of space above each leaf. There are ideal ranges depending on the difference between ambient humidity and leaf surface humidity! Fans blowing directly on your plants from above will measure a max humidity difference, while still air shows little to none.

Using any of the general charts will give you acceptable results, but more detail is out there, I encourage exploration!

This is an amazing resource! Thank you!

 

[Bush Doctor 77]

The VPD chart for pot and lettuce would be vastly different. My greenhouse is often above 100F and below 30% RH. I grow tree-like plants. This weed grows well from the tropics to the desert.