Anyone ever go a full bloom cycle using VPD guidelines?

If you're unfamiliar with VPD, here is an informative read...
http://www.just4growers.com/stream/temperature,-humidity-and-c02/vapor-pressure-deficit-the-hidden-force-on-your-plants.aspx
The obvious concern would be molds, fungus and bacterias. On the plus side it seems it'd be more efficient with energy consumption and in most cases ease of operation.

Running above 60 % RH indoors is going to be problematic unless in a greenhouse or facility built to endure this type of weathering . Its been noted that many strains of cannabis produce and perform poorly with high humidity during flowering . I have seen this first handed with proven cuts . There is a reason most people tend to be alarmed at anything over 50% during flower as this is a good average when considering all of the odds . Now do not get me wrong , I have a few proven ladies and some land races that will do best with a high humidity during flower .. Ceph , explore and learn but do always maintain a constant air exchange with plenty of circulation and you ll find a world of variables when growing different genetics . I tend to just go with the flow and rarely due I override and intervene ... Peace .PotSnob

Thx for the reply PPS. in regards to air exchange would you say a (near) sealed room with good air circulation, dehumidifier, gas fire co2 and mini-split operating at 80-81degrees, 65-70rH, 1250-1500ppm co2 (sentinel operated) and 1k outputs are acceptable conditions? I've always stayed about 45-50rH, but this is intriguing. If things get to scary I can always dial down and I have a S-burner on the read at the first signs of trouble. I all ready kinda figured I'd probably chicken out in the final weeks and dial it down anyhow. The more I've read about this, the more I've become to think it's about having good flow throw your canopy. Regardless, there still are inherent dangers running your op like this. Thx again for the words of caution.

I ran sealed a few years back and found that-- for one every thing is relative, for two high humidity 75 high temp 82 high co2 1500, ppm 1400 gave me staggering results but the high humidity must be removed at lights off I went down to 40 also at week five the humidity must not exceed 55 or your asking for a whole lot sadness. Humidity is a much over looked key to fast growth, higher the humidity the more ppm you can run as the plant moves less water because of evaporation being reduced. Your salt content in the plant is higher allowing the osmosis to work in the 1400-1500 ppm range with no burn --- I use r.o water so 1400-1500 ppm of hydro salt is hot. Man what a lot of work all that was I have since seen the light just a bag of dirt and a fan.

I do, and always will.

1150 ppm on c02, room temps @ 85 with 65 - 75 rh in veg and
first 3 weeks flower. Weeks 4-7, 80 degrees rh @ 55-60 and week
8-9 75 degrees 50% rh.

You HAVE to be burning Co2 for this to have any positive effect. Higher temps
and humidity will open the plants stoma and will allow for better absorption.

There is a mold resistant sheet rock made now, along with a few coats of kilz paint
and a vapor barrier that I am hoping will help in not turning my basement into a petri dish.

same chart different color. my bad

cephalopod said:

Thx for the reply PPS. in regards to air exchange would you say a (near) sealed room with good air circulation, dehumidifier, gas fire co2 and mini-split operating at 80-81degrees, 65-70rH, 1250-1500ppm co2 (sentinel operated) and 1k outputs are acceptable conditions? I've always stayed about 45-50rH, but this is intriguing. If things get to scary I can always dial down and I have a S-burner on the read at the first signs of trouble. I all ready kinda figured I'd probably chicken out in the final weeks and dial it down anyhow. The more I've read about this, the more I've become to think it's about having good flow throw your canopy. Regardless, there still are inherent dangers running your op like this. Thx again for the words of caution.

Click to expand...

Glad to chat about this subject as it intrigues me too my friend . I used to run a sealed room with a harvest grow and would allow humidity to climb upwards of 70% RH during the transition into flowering but am no longer even able to think of such do the risks involved with a perpetual . Not sure if your growing with a perpetual or not . Once one decides to maintain a perpetual grow it is best to maintain ideal temp and RH at all times due to the varying stages of development . I Do though take advantage of VDP in my vegative tent but really would not advice doing so past a few weeks into flowering as most cannabis strains will develop excessive leaf development and a decrease in trichome production from my own experience . But as I mentioned there are some genetics that would actually flourish in this type of environment .. The old Vietnamese Black is one that comes to mind , damn jungle weed lol .. Thanks for the post .....

ProfessorPotSnob said:

Glad to chat about this subject as it intrigues me too my friend . I used to run a sealed room with a harvest grow and would allow humidity to climb upwards of 70% RH during the transition into flowering but am no longer even able to think of such do the risks involved with a perpetual . Not sure if your growing with a perpetual or not . Once one decides to maintain a perpetual grow it is best to maintain ideal temp and RH at all times due to the varying stages of development . I Do though take advantage of VDP in my vegative tent but really would not advice doing so past a few weeks into flowering as most cannabis strains will develop excessive leaf development and a decrease in trichome production from my own experience . But as I mentioned there are some genetics that would actually flourish in this type of environment .. The old Vietnamese Black is one that comes to mind , damn jungle weed lol .. Thanks for the post .....

Click to expand...

That's it right there. I would have no worries running higher RH the first few weeks of flower IF I didn't have other plants finishing up beside them. I would have bud-rot 100% guaranteed if my RH was over 55% the last few weeks of flower.

Interesting topic though ceph. Thanks for posting that link.

Lol at my typo .. This bloody orange bud really fucks with my motor skills lol

While we're talking science here, what's gained by dropping co2 levels late in flower. I've always ran perpetual too and it kept me from explorering this factor as well, but I do hear it talked about.

I cut it off completely the last week. It's a taste thing from my understanding.
I have heard of others reducing down to 500 the last 10 days but, I have not
tried it yet.

Some plants will just keep budding and not finish. just my experience I don't know how common it is for plants to respond Like this. Heavy yielding strans I believe are more prone to it. I dropped the hydro sealed co2 thing On the quest for potency so my experience is limited on co2. I started cutting the co2 10 days or so b4 harvest like most.