VPD Chart Guidline

Was looking stuff up about growing and such I came across this chart. Just interested in what y’all know about it? Do y’all follow it? Or is it just a “let’s get close” to it? I’ve read a shoot load of forums and never seen this till now.

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It’s a big thing here. You’ll see it all over on threads. It can be difficult to maintain the perfect vpd but when you do the growth is pretty explosive. I use this chart because I don’t do well with colors


Some try to follow it as closely as possible. I don’t really worry about it much and with my tents in my bedroom, I’m never going to have the humidity as high as the chart would suggest (too muggy for me and wife), I’m more than happy with the way my plants grow in the 40-50 RH range or less even. I’ve done complete grows in 25-35 RH as well with no problems before using humidifiers to up it a bit, I live in the desert where it’s usually 20 RH or less outside.


I live in Redneckville where they run the horses once a year. I’m new at this stuff but I try to research all I can about a strain I wanna try and I’ve never seen this.
I did save bobbydigital chart and compare it to what I have.
Thanks a bunch

I’m glad this question was asked. I also was wondering how great of a difference there would be. I’d love to see the study where multiple clones are under all the same conditions with the only controlled change being VPD out of range and see it’s effects.

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Only major difference you’ll see is much faster growth when you nail the vpd. There are times of the year when I can keep a perfect vpd throughout the grow and then other times of the year where I’m outside of optimal. When it is optimal, I can get the plants to the size I want and flip to flower in 6 weeks. When it’s not optimal it can take 8-10 weeks to get them the size I want.


Thanks @BobbyDigital I find that hugely helpful!

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Seems risky for wpm…too scared to try but def during veg i follow the chart.

It is if you’re in the higher temp range in late flower. But if you can get down to around 76 you’re good.



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What do you do with the pressures at the top of the chart? The .8 and 1.1 at this time. I think I’m starting to dial in my light and temp/humidity is next.

Those pressure readings are those humidity levels at a certain temp. As long as your humidity levels and temp on the chart are equal, then you’re hitting your pressure level (vpd)

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Gotcha, thanks🤘

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this seems to be something even a beginner can adjust to. good info