VPD and why care

[KGBSkunky]

It’s called vapor pressure deficit and I had no idea what it meant but it is calculated as one of the three things you need to track. Which are Temperature Humidity and of course VPD which are all tracked by my AC Infinity controller. It appears my perception of temps and humidity might have to be altered. This is one of the main things they teach in a college when the course is growing cannabis.

So what does it mean?

It’s all about hitting the correct VPD range in both vegetative and flowering stages, and they are different ranges, so that the plants can “perspire” properly thus promoting the best possible health. I am currently playing around with this so I can see the proper way to manipulate the temps and humidity and hit that range easily. Look at the graph I put up earlier. As the heat and humidity changed so did the VPD which should be .8 to 1 or so for perfect perspiration conditions when in the vegetative state.


Information on VPD

 

[KGBSkunky]

And if you misunderstand how a plant “breathes” take this awesome high magnification short video of a leaf breathing. And no this isn’t doctored.

 

[pute]

Interesting.

 

[pute]

When you come up with the info you seek please share. My conditions change with the seasons. When the furnace runs the humidity and and temps are lower. In the summer just the opposite. Difference is the yield is better in the summer but the bud quality seems to be the same.

 

[bigsur51]

it is amazing how Mother Nature dials it all in eh…outdoors

temperatures , humidity , VPD , photosynthesis

it is a miracle

just set it and forget it

 

[KGBSkunky]

it is amazing how Mother Nature dials it all in eh…outdoors

temperatures , humidity , VPD , photosynthesis

it is a miracle

just set it and forget it

 

[KGBSkunky]

I understand the point you are attempting here so let me just explain where I am attempting to go with this. The set it and forget it rule will work just fine. To Pute’s point his yield may vary but the cannabis is good either way. I understand this. What I want to see is how it turns out if the conditions are near perfect.

An added bonus is, as per the university classes, your chance of getting bud rot is almost zero.

If you didn’t somehow get a bonus with advanced systems it the corporations wouldn’t do it as it would be considered a non value added process. So what’s the value they see in adding full environmental control and why don’t I want it also? Seriously do you know because I don’t but it’s why I went with a tent.

Also note that there are, apparently, lots of calculators and apps for determining VPD

 

[bigsur51]

It is all good Amigo.

thanks for the information , i appreciate it

VPD , IMP , Quality Assurance VP’s running around inspecting things , complying with Industry Standards

all this data and info is used by the corporations to improve their bottom line, period.

and i agree

some of the corporate commercial grows are in insanely huge!!…millions of sq feet , all indoors!

in those situations , if they can get one plant to produce 5 more grams by adding full environmental controls , it is easy to do the math with a million sq feet to work with and come to an obvious conclusion…more product = more money

and by lowering the chances of getting powdery mildew , plants are saved which improves the bottom line


you said , “ i want to see how it turns out if the conditions are near perfect.”

are you talking about your tent grow?

my apologies if you have a grow thread going here , if so i need to check it out

 

[pute]

Well .....

 

[CrashMagnet]

From his previous posts, I think it's a small grow tent. It would be easier to use a room AC and dehumidifier to set a course value, then tweak VPD inside the tent with temperature by adjusting the vent fan speed. I still don't think a humidifier is needed for a tent in Maryland when you look at the VPD charts for cannabis.

 

[pute]

Prices are at rock bottom here. If you sell better product currently and are fighting a competive market what is the break even cost to sell perfect pot?

 

[KGBSkunky]

Just getting everything setup for July 1st then I will start a thread on how it all turns out. I am retired and this whole project is just too cool.

 

[CrashMagnet]

What will you do for a control? In effect, how will you know holding the perfect VPD was useful?

 

[KGBSkunky]

Prices are at rock bottom here. If you sell better product currently and are fighting a competive market what is the break even cost to sell perfect pot?

AHH finally figured out the quote

No no this is just for me and whomever I gift. I feel the commercial growers final product is inferior to what I can produce due to shortcuts they take for curing and storing.

 

[bigsur51]

From his previous posts, I think it's a small grow tent. It would be easier to use a room AC and dehumidifier to set a course value, then tweak VPD inside the tent with temperature by adjusting the vent fan speed. I still don't think a humidifier is needed for a tent in Maryland when you look at the VPD charts for cannabis.

we did a little better indoor growing back in the day and had controllers in the rooms to monitor temps , humidity , turned all the equipment on and off to maintain the desired parameters

but that has been a few years ago and technology has changed

yeah , if i was managing lets say an indoor with 25 or more plants i would invest in a current controller , im not sure if this is one , but yeah , total control and i can sleep at night

 

[KGBSkunky]

What will you do for a control? In effect, how will you know holding the perfect VPD was useful?

I can see I am distressing you somehow with this subject and that wasn't my intention so let me show you the other issue I have with this. First I am retired and this is an interesting project that appears to be as automated as I want to make it which is what I am looking for. I will only be able to grow two plants at a time which, unless I want to test individual plants, means feminized seeds and for at least my first grow autoflowers. The time to do a full grow is still 3-4 months and I would like to ensure that I have the least amount of issues and no bud rot.

As for a control why would I need one? I have nothing to prove to anyone nor am I considering a speaking tour or book deal

 

[bigsur51]

I can see I am distressing you somehow with this subject and that wasn't my intention so let me show you the other issue I have with this. First I am retired and this is an interesting project that appears to be as automated as I want to make it which is what I am looking for. I will only be able to grow two plants at a time which, unless I want to test individual plants, means feminized seeds and for at least my first grow autoflowers. The time to do a full grow is still 3-4 months and I would like to ensure that I have the least amount of issues and no bud rot.

As for a control why would I need one? I have nothing to prove to anyone nor am I considering a speaking tour or book deal

congratulations on retirement!

woot! woot!

we have a few of us on this Forum

i like your approach to gardening , if one is going to do something , they may as well do it right

and it doesnt matter whether it is 4 plants or 4000 , the commitment to excellence is the same

 

[KGBSkunky]

congratulations on retirement!

woot! woot!

we have a few of us on this Forum

i like your approach to gardening , if one is going to do something , they may as well do it right

and it doesnt matter whether it is 4 plants or 4000 , the commitment to excellence is the same

I like to think of it like if I was a drinker I would have been making 5 gallons of alcohol and barreling it once a year from select ingredients at peak time.

This is me about to do that utilizing cannabis as I have to have it to control my ADHD anyway

But this I promise you. When I reveal my auto watering setup it will be nothing you have ever seen before...that's gotta be a bold statement on a grow site!

 

[CrashMagnet]

I can see I am distressing you somehow with this subject and that wasn't my intention so let me show you the other issue I have with this. First I am retired and this is an interesting project that appears to be as automated as I want to make it which is what I am looking for. I will only be able to grow two plants at a time which, unless I want to test individual plants, means feminized seeds and for at least my first grow autoflowers. The time to do a full grow is still 3-4 months and I would like to ensure that I have the least amount of issues and no bud rot.

As for a control why would I need one? I have nothing to prove to anyone nor am I considering a speaking tour or book deal

No, it's interest. I'm really not one to get distressed over much of anything. I asked about a control, because I'm interested in how maintaining the ideal VPD will impact your results in a small grow. If I had thought of it instead of grafting, I would be doing the same as you right now.

 

[oldfogey8]

Getting your environment under control will certainly help eliminate one issue a lot of us battle. My guess is having plants in the tent will change the dynamic because of their transpiration. To dial things in before you can legally grow weed, maybe consider starting some tomato or pepper plants. You can get a head start on a vegetable garden. I agree with crash on getting the room your tent is in stabilized will make your tent that much more stable and easier to control since all the air in the tent will be coming from the room. The auto watering thing could be difficult since the plants don’t necessarily drink the same amount throughout the growth cycle. Plus it is good to get a feel for the wet/dry cycle the plants like.