# VPD THREAD? Vapor Pressure Deficit information needed!!



## Deathpack (Sep 14, 2017)

Hello, 


I am a beginner level grower, and am taking on my first rodeo  hahaha...after months of observation, years of connoisseuring and lifetime love for all things botany. I've decided to take on a few methods that most growers do not practice... I've been reading up on transpiration, and have been looking for ways to keep my VEG room on point when it comes to how much moisture is in the air.. i've added some humidifiers to the rooms , and am constantly checking temps/RH to make sure i don't step foot into a danger zone... ANY TIPS?

_MAIN VEG - 75* F
51% RH

ROOM 1 - 80* F
53 % RH
_
*Note: I transplanted a few plants from veg (at about 2 - 2 1/2 feet tall) into 15 gallon smart pots.. I plan to veg them for another 2-4 weeks..


Any help or tips would be greatly appreciated...


~ death *
_ 
_


----------



## chemphlegm (Sep 14, 2017)

over thinking it man. relax

humidifier, dehumidifier, ac, air scrubber, moving air, fresh air/c02 and heat controlled=success


----------



## Deathpack (Sep 14, 2017)

chemphlegm said:


> over thinking it man. relax
> 
> humidifier, dehumidifier, ac, air scrubber, moving air, fresh air/c02 and heat controlled=success


i overthink things lol...good info, thanks


----------



## Sureshot2 (Sep 14, 2017)

For those temps your RH seems a bit low to me. I run at 65% RH with air temps between 75-77f and even that I think is a bit on the low side for proper VPD.


----------



## ruwtz (Sep 14, 2017)

Deathpack said:


> i overthink things lol...good info, thanks


You probably don't wanna hear this, first rodeo and all. And I get it cos i've been there, but honestly it is sound advice.

You can easily tie yourself in knots chasing VPD in the name of perfection. I know I did.

Some might disagree but in my opinion the solid science behind much of VPD research isn't so applicable to our beloved plant here, and fighting to hit the 'zone' found on some chart could even hurt your girls. You might easily find those humidity numbers relative to temperature are just way too high and much more suit leafy veggies and fruiting plants.

I run similar temps/humidity as you and my garden never misses a beat. I don't sweat minor swings and plants are always happy and vigorous. You'll find people running all kinds of temps/humidity variables with great success, proof if it is needed that there is no absolute in VPD in relation to cannabis.

My advice would be to put your good mind to more critical things like light intensity, air flow, watering regimen and plant training.


----------



## Deathpack (Sep 14, 2017)

ruwtz said:


> You probably don't wanna hear this, first rodeo and all. And I get it cos i've been there, but honestly it is sound advice.
> 
> You can easily tie yourself in knots chasing VPD in the name of perfection. I know I did.
> 
> ...


Great response thank you so much, if you ever come across one of my posts again please feel free to comment, as I am a big believer in constructive criticism as long as it is positive. 

Thanks


----------



## GreenSanta (Sep 14, 2017)

also some small scale growers might end up with mold in all corners of their houses trying to chase VPD, ... indoor grows are not like greenhouses. I am happy at 45-55% RH regardless of temps.


----------



## Deathpack (Sep 14, 2017)

GreenSanta said:


> also some small scale growers might end up with mold in all corners of their houses trying to chase VPD, ... indoor grows are not like greenhouses. I am happy at 45-55% RH regardless of temps.


oh that i was sure of haha, but it was for a room that is comfortably housing 225 gallons of soil in an insulated super clean, super controlled environment.. I realized i was stressing this issue too much, currently vegging with 2 of the 9 lights on, as i'm looking to install mini splits this weekend... was just freaking out a little haha ... but my room is currently at 81* F and has an RH of 55%.. thanks for all the great tips!!! your replies are greatly appreciated


----------



## ruwtz (Sep 15, 2017)

Deathpack said:


> oh that i was sure of haha, but it was for a room that is comfortably housing 225 gallons of soil in an insulated super clean, super controlled environment.. I realized i was stressing this issue too much, currently vegging with 2 of the 9 lights on, as i'm looking to install mini splits this weekend... was just freaking out a little haha ... but my room is currently at 81* F and has an RH of 55%.. thanks for all the great tips!!! your replies are greatly appreciated


Lets check in on that 'super controlled' part when you have everything turned on full blast and crammed witg vigorously flowering plants 

Good luck with it all!


----------



## zypheruk (Sep 15, 2017)

I personally think all this vpd shit etc is something 90% of home growers growing in tents will never nail, way to many variables, now if your growing in a sealed room then yes you should be able to nail it easy enough.
I may be totally wrong and talking shit that my cf filter ain't filtering..


----------



## RM3 (Sep 15, 2017)

VPD is a waste of time, as the charts floatin around are not about cannabis (as has been stated) and even if they were it would require replicating the test environment to duplicate

The best way to get cannabis in the zone is to adjust for a heat index 4 points above ambient


----------



## Carolina Dream'n (Sep 15, 2017)

I run my veg room at 86 degrees 75% humidity, 1300 ppm co2. 
Flower room starts at that and slowly starts ramping down to 77 degrees 50%, 800 ppm co2 by the last week. 

VPD only works if you are supplementing co2 in my opinion. The results are amazing once it's dialed in. 1-2 inches of growth a day in veg.


----------



## Jaybodankly (Sep 15, 2017)

You are putting in the right effort to control your grow environment. The more control you have the better grower you will be. I recommend a data logger. I use a Sensorpush $50. There are others. Maybe be better ones. Havent looked in awhile. They are temp/hum sensors that send text to your phone if it falls out side the hi/low settings. The app provides a nice graph chart hour, day, week, month, year.


----------



## Deathpack (Sep 15, 2017)

Jaybodankly said:


> You are putting in the right effort to control your grow environment. The more control you have the better grower you will be. I recommend a data logger. I use a Sensorpush $50. There are others. Maybe be better ones. Havent looked in awhile. They are temp/hum sensors that send text to your phone if it falls out side the hi/low settings. The app provides a nice graph chart hour, day, week, month, year.


Awesome tip! Thank you so much for your kind words..... your help is appreciated..  If i could like posts id hit the thumbs up haha


----------



## Deathpack (Sep 15, 2017)

Carolina Dream'n said:


> I run my veg room at 86 degrees 75% humidity, 1300 ppm co2.
> Flower room starts at that and slowly starts ramping down to 77 degrees 50%, 800 ppm co2 by the last week.
> 
> VPD only works if you are supplementing co2 in my opinion. The results are amazing once it's dialed in. 1-2 inches of growth a day in veg.



Setting up my co2 tanks along with the AC units this weekend hopefully... working with what i have to keep the girls as pretty as they can be, i will be sure to include some pictures soon... thanks for the feedback


----------



## Deathpack (Sep 15, 2017)

zypheruk said:


> I personally think all this vpd shit etc is something 90% of home growers growing in tents will never nail, way to many variables, now if your growing in a sealed room then yes you should be able to nail it easy enough.
> I may be totally wrong and talking shit that my cf filter ain't filtering..


haha its alright we all have our own opinions, i understand that some people don't like to follow VPD charts , or don't believe in them.... but I feel that transpiration plays a big role in how any plant grows... then again that could be my shit filter haha , just gonna have to wait and see...thanks for the feedback


----------



## Deathpack (Sep 15, 2017)

ruwtz said:


> Lets check in on that 'super controlled' part when you have everything turned on full blast and crammed witg vigorously flowering plants
> 
> Good luck with it all!


Thank you for the support


----------



## ruwtz (Sep 15, 2017)

Carolina Dream'n said:


> I run my veg room at 86 degrees 75% humidity, 1300 ppm co2.
> Flower room starts at that and slowly starts ramping down to 77 degrees 50%, 800 ppm co2 by the last week.
> 
> VPD only works if you are supplementing co2 in my opinion. The results are amazing once it's dialed in. 1-2 inches of growth a day in veg.


I'm keen to see this in action, thats real high supplemented CO2 in veg! It is said fairly regularly that high CO2 in veg stunts stomata development with obvious hindrances throughout the rest of the growth cycle, but I don't know about it as I don't add CO2 in veg.


----------



## Deathpack (Sep 15, 2017)

ruwtz said:


> I'm keen to see this in action, thats real high supplemented CO2 in veg! It is said fairly regularly that high CO2 in veg stunts stomata development with obvious hindrances throughout the rest of the growth cycle, but I don't know about it as I don't add CO2 in veg.


It's good to add CO2 in any stage of any plants life , helps with growth if you know what you're doing.. the only CO2 my girls are getting are from their bedtime stories haha, until i set everything up this weekend haha!


----------



## Huckster79 (Sep 15, 2017)

I like vpd as a rough guide, just do go nuts chasing it like its the word of the lord, its a guide... the concept makes perfect sense. What i do is try to roughly follow it until about 3 weeks from finish, then use a week to transition to bone dry and cool finish. Remeber vpd concept is for overall plant health, your goal in last few weeks isnt overall plant health, as shea done growing as a plant, you now want conditions ideal for bud finishing and ripening..


----------



## Deathpack (Sep 15, 2017)

Huckster79 said:


> I like vpd as a rough guide, just do go nuts chasing it like its the word of the lord, its a guide... the concept makes perfect sense. What i do is try to roughly follow it until about 3 weeks from finish, then use a week to transition to bone dry and cool finish. Remeber vpd concept is for overall plant health, your goal in last few weeks isnt overall plant health, as shea done growing as a plant, you now want conditions ideal for bud finishing and ripening..


Thanks for the feedback... great info , will be sure to keep in mind!


----------



## Huckster79 (Sep 15, 2017)

I was a nube like you, i wanted more of a goal than just finish w live plant and a nug... i did all sorts of shit my first grow and learned lots by diving in deep... my best advice is triangulate off all the diff advice you get to make your own style, take nothing to extreme, do ny change slow, and ignore ppl's advice who tout their way as the only way..

I think part of it is if your into botany youve grown something else before, many new growers have never grown a marigold so the simple get to finish w a smokable nug may be a solid goal for them...


----------



## ruwtz (Sep 16, 2017)

Deathpack said:


> It's good to add CO2 in any stage of any plants life , helps with growth if you know what you're doing.. the only CO2 my girls are getting are from their bedtime stories haha, until i set everything up this weekend haha!


Not true. Ambient CO2 levels - typically 400ppm - in veg are more than sufficient.

Elevated CO2 levels restricts stomata density https://www.sciencedaily.com/releases/2011/03/110303111624.htm

Elevated CO2 levels constrain nitrogen acquisition
http://onlinelibrary.wiley.com/doi/10.1111/gcb.12938/abstract


----------



## Shugglet (Oct 8, 2017)

ruwtz said:


> Not true. Ambient CO2 levels - typically 400ppm - in veg are more than sufficient.
> 
> Elevated CO2 levels restricts stomata density https://www.sciencedaily.com/releases/2011/03/110303111624.htm
> 
> ...


The problem I have with the first study is that, if youre running CO2 at 1000-1500 ppm, you are 2-3x higher concentration levels than natural. Even if stomata density is reduced by ~30%(varies by plant) I would think the fact youre dealing with a 100-200% increase in co2 level would result in a net increase in available usable CO2 to the plant assuming no other bottlenecks. So in other words, while 400 probably is sufficient, elevated will increase the overall potential.

Also a good reason why people running CO2 run higher temps, because they open the stomata.


----------



## ruwtz (Oct 8, 2017)

Shugglet said:


> The problem I have with the first study is that, if youre running CO2 at 1000-1500 ppm, you are 2-3x higher concentration levels than natural. Even if stomata density is reduced by ~30%(varies by plant) I would think the fact youre dealing with a 100-200% increase in co2 level would result in a net increase in available usable CO2 to the plant assuming no other bottlenecks. So in other words, while 400 probably is sufficient, elevated will increase the overall potential.
> 
> Also a good reason why people running CO2 run higher temps, because they open the stomata.


Interesting presumption, and worthy of some testing if you're up for it.

Also, higher temps with CO2 are beneficial due to increased rapidity of metabolic processes, not necessarily opening stomata. In fact, under water stress, stomata will just as easily close at higher temps.


----------



## pop22 (Oct 10, 2017)

I'd shoot myself before having all that crap in my growroom! If I wanting to work in a lab, I'd get a job in one! Growing at home isn't all about the almight gpw, its really about quality and the enjoyment of watching your plants develop. 

But to each his own, that's simply my feelings on it, so if you enjoy this style of growing, cool! I hope it brings you satisfaction! Myself, the simpler I can make my grow, the better.



Jaybodankly said:


> You are putting in the right effort to control your grow environment. The more control you have the better grower you will be. I recommend a data logger. I use a Sensorpush $50. There are others. Maybe be better ones. Havent looked in awhile. They are temp/hum sensors that send text to your phone if it falls out side the hi/low settings. The app provides a nice graph chart hour, day, week, month, year.


----------



## Jaybodankly (Oct 11, 2017)

"If youre running CO2 at 1000-1500 ppm, you are 2-3x higher concentration levels than natural".

My understanding is plants evolved under much higher levels of CO2 and heat for millions of years. Growing indoor is not natural. Creating better conditions for perfect growth than available outside is not natural. Creating an excellent growing environment is what we strive to do.


----------



## whitebb2727 (Oct 11, 2017)

I've never worried about vpd. I actually prefer my humidity lower than most recommend. 40% range.


----------



## ChaosHunter (Oct 11, 2017)




----------



## Huckster79 (Oct 11, 2017)

Id say the range given for late veg should be carried through the begining of flower, say 3 or 4 weeks even... lowers the stress of the flip as one less change, but i think really helps em grow in that rapid stage of development, once plant starts to be relatively fully formed and further growth will be more in a swelling and enlarging type of growth vs fresh new growrth then transition to drier and drier air... there is zero reason that rh needs to drop the night of the flip...but finish dry oh hell yea.. and a drop in temp to i prefer towards the end... i do my temp like i do my humidity dont change it day of flip... give it that warmth for the growing part of flower and cool temps w bone dry air... god i can almost taste the results of that just thinking about it... time to quit just thinking about it


----------



## Heber (Feb 1, 2018)

Deathpack said:


> Hello,
> 
> 
> I am a beginner level grower, and am taking on my first rodeo  hahaha...after months of observation, years of connoisseuring and lifetime love for all things botany. I've decided to take on a few methods that most growers do not practice... I've been reading up on transpiration, and have been looking for ways to keep my VEG room on point when it comes to how much moisture is in the air.. i've added some humidifiers to the rooms , and am constantly checking temps/RH to make sure i don't step foot into a danger zone... ANY TIPS?
> ...


Vpd range u r shooting for is different thru different cycles. 1-4 for early veg, 4-8 late veg, 12-14 early/mid flower, 16-17 late flower here's a chart


----------



## Heber (Feb 1, 2018)

Shugglet said:


> The problem I have with the first study is that, if youre running CO2 at 1000-1500 ppm, you are 2-3x higher concentration levels than natural. Even if stomata density is reduced by ~30%(varies by plant) I would think the fact youre dealing with a 100-200% increase in co2 level would result in a net increase in available usable CO2 to the plant assuming no other bottlenecks. So in other words, while 400 probably is sufficient, elevated will increase the overall potential.
> 
> Also a good reason why people running CO2 run higher temps, because they open the stomata.


High co2 levels actually temper the atomata openings , with the plant thinking it has enough co2 uptake, same reason plants grown under elevated co2 have lower stomata density... if plants are grown at atmospheric co2 thru veg (when leaves r forming)theoretically they will have normal stomata density... also, just my own theory I'm testing, reducing co2 to ambient half (600-700)of normal I run, for 7 days following defoliation (will keep posted on that)


----------



## Kami Samurai (Nov 11, 2018)

Bump about to share the vpd information I’ve read.


----------



## ANC (Nov 11, 2018)

I make sure to photograph my plants along with the meter readings when I am happy with their performance.


----------

