For you folks obsessed with humidity, some valuable information MUST READ!

[ttystikk]

Great info... Have plants that do great in low humidities.. 20-30, anything over 40 percent rh and they start doing worse and may even develop PM!! Terrible because humidity is hard to control in the winter time especially where I'm at! Summer time is a whole lot better.

I'm getting tired of shooting this MYTH down, over and over. RH does not contribute to fungal problems until your environment gets on the wrong, or damp side of the VPD chart. I've gotten a nasty case of powdery mildew in a grow room that never saw humidity values higher than 30%. It was caused by a lack of foliar spraying(!) and poor air circulation. In fact, many local gardeners actively spray their outdoor cucumbers, zucchini and squash leaves daily, specifically to keep powdery mildew at bay.

 

[rawman]

Its from agrowtech msrps at like 1500$ or so.... /its their old model I am not even 100% that they make it anymore, but their new ones still watch VPD

 

[greendreams]

hm... interesting info. definitely something to think about.

 

[woodsmaneh]

VPD CALCULATOR
http://www.autogrow.com/vpd_calc.php

 

[neverbreak]

some good info in that article.

neverbreak

 

[craftymofo]

Growtronix Can monitor, chart, and control VPD.

 

[craftymofo]

For under 600 bucks.

 

[Beasters X Haze]

so what happens with night time humidity when using that chart?

 

[caveman4.20]

Im not a 100 % but IME healthy plants will push 100% rh if its not vented so that tells me that plants have no issue transpiring and thats due to low leaf temps at night im sure someone else could explain it better if you want I can elaborate if your interested in my experience based opinion!

 

[ttystikk]

Im not a 100 % but IME healthy plants will push 100% rh if its not vented so that tells me that plants have no issue transpiring and thats due to low leaf temps at night im sure someone else could explain it better if you want I can elaborate if your interested in my experience based opinion!

There is some transpiation continuing at night. Mostly though, rh rises because temps fall, reducing the sites ability to hold moisture. Running a dehuey helps as much because they pull out heat as because they're removing humidity!

 

[caveman4.20]

There is some transpiation continuing at night. Mostly though, rh rises because temps fall, reducing the sites ability to hold moisture. Running a dehuey helps as much because they pull out heat as because they're removing humidity!

I agree and so many benefits from venting that extra humid out just as long as it dosent get too cold or too hot (for dif growers) ...my .02 peace

 

[craftymofo]

I'm getting tired of shooting this MYTH down, over and over. RH does not contribute to fungal problems until your environment gets on the wrong, or damp side of the VPD chart. I've gotten a nasty case of powdery mildew in a grow room that never saw humidity values higher than 30%. It was caused by a lack of foliar spraying(!) and poor air circulation. In fact, many local gardeners actively spray their outdoor cucumbers, zucchini and squash leaves daily, specifically to keep powdery mildew at bay

Good info just add on top of that is that healthy plants are less likely to allow pm to grow, so keeping optimal vpd can help in that way also.

 

[ttystikk]

Good info just add on top of that is that healthy plants are less likely to allow pm to grow, so keeping optimal vpd can help in that way also.

It's been my experience that this is true, due perhaps to lower stress experienced by the plant under conditions of more optimal humidity- in the local case, substantially higher than ambient.