VPD. How important is it?

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Ganjier

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Hi everyone. Hope all is well. I wanted to take a minute and talk about how implementing VPD in my grow tent has made an improvement on my current grow over my last grows where I never followed a VPD chart.
First off, it has not been a easy task to stay in the "green" zone to say the least, but with help from humidifiers and dehumidifiers it has become doable. I don't know how much money it would take me to implement this into a grow room vs a grow tent. The tent was hard enough to dial in.
Also I have only implemented this during the flower phase. I did not have my tent dialed in during veg.
The biggest thing I noticed was that I can now let my 2 gallon coco medium go 3 days before feeding again with no signs of any issues. This is a BIG no no in the "coco" world. They are not drinking as much as they were previously. I also noticed that the plants at 4 weeks in flower have shown more pistils and more bulking of flower over any other grow, including stacking. I know this may be strain dependent, but either way I do not foresee me going back to just "winging" my temps and humidity.
In the world of growing cannabis in flower I have been told to stay below 80 ish degrees and keep my humidity under 50%. I am running my lights at 100% with an ambient temp of 83- 85 with humidity upwards of 57-60%. I make sure I have adequate air movement as to not grow any mold. So far I am very impressed with the conditions of my plants. 4 weeks in and they have a very greasy feeling to them when I rub the sugar leaf to get a smell of the terps and the smell alone is crazy. I also noticed that my house reeks. I have never had my area so pungent even late in flower let alone 4 weeks in.
I realize that it is hard for me to compare the grow since this is the first time I am running these genetics, but I can 100% guarantee you I will be continuing this in the future.
I feel like cannabis growers have been brainwashed into thinking they need to keep their humidity below 50% because they are afraid of losing their crop. I think as long as you have good air movement you should be fine at these numbers.
Now, what is also nice about this VPD flower chart is you don't have to run my numbers. If your temp is higher or lower you just follow the humidity percentage to keep you in that green range. The lower your temp the lower the humidity, and vice versa. I will be dropping my light percentage to around 50-60 percent during the last week in flower which will allow me to drop my humidity percentage. This will hopefully help with color and help to avoid too much moisture in my flower.
I just wanted to share my experience thus far regarding this topic. I will be adding more info on any apparent differences I may notice as the grow comes to an end. Hopefully this can help someone with taking their grow to the next level if they choose to do so. I feel it does make a big difference in the plants as it allows the stomata to work the way it should.

https://pulsegrow.com/blogs/learn/vpd-charts-in-fahrenheit-and-celsius-with-leaf-temperature
 
You know I've never in my life had a grow room that was under 60 percent humidity. I've also always ran higher than normal temps and more light than I needed. My vpd was good before I even knew what that was. Now that I have a vpd monitor I understand why I've always had such rapid growth. My vpd is always in the green with lights on with the help of the fan controller as well.
 
You know I've never in my life had a grow room that was under 60 percent humidity. I've also always ran higher than normal temps and more light than I needed. My vpd was good before I even knew what that was. Now that I have a vpd monitor I understand why I've always had such rapid growth. My vpd is always in the green with lights on with the help of the fan controller as well.
Glad you chimed in. 60% through the end of flower? If so that's good. I may just let the light fire through the end at 100%, or close to.
How do you feel about drying at higher humidity?
 
Glad you chimed in. 60% through the end of flower? If so that's good. I may just let the light fire through the end at 100%, or close to.
How do you feel about drying at higher humidity?
You would need extra airflow and possibly a little bit warmer
 
same here

with that being said , i would much rather grow in low humidity , i am talking 5-10% , than to fight high humidity and mold

misting plants with water is an easy way for me to raise humidity or some buckets of water in the growroom
Yup I live at sea level between a bayou and a swamp Forrest. Humidity outside often reaches 100pct
 
Based on those charts I routinely run low humidity. Temps around 80 degrees and below 50% RH. I think I will unplug the dehumidifier and see if the plants drink less. Any chance that has contributed to the late flower crispy leaf issue?
 
Ganjier may be on to something with the silica supplementation. I knew it helps with cell wall strength and thus stem strength but in looking around the whirled wild infernet, I see sites saying it helps prevent fungal infection, increases nutrient uptake and moisture retention(which would explain the plants ‘drinking less’ I think). I think Bubba and pute both use silica supplements but I could be wrong.
 
Everyone of my grows have run in the 80’s with over 50% humidity. In a small tent I have to ensure defoliation is done as I usually crowd my tent but I’ve had no humidity issues and my plants seem to adapt well to the higher humidity and temps.

edit. Also some of my plants drink more than others in these conditions and I think that would happen no matter what your humidity settings were. Every plant is different…
 
Based on those charts I routinely run low humidity. Temps around 80 degrees and below 50% RH. I think I will unplug the dehumidifier and see if the plants drink less. Any chance that has contributed to the late flower crispy leaf issue?
Well I’ve had the crispy leaf issue at the end of flower at higher than 50% humidity. I don’t think so but never did figure out what caused it only guesses.
 
I'll have to try silica next. I probably have some silica product or two already laying around the shop. I used to buy stuff all the time without knowing if I needed it (Used to, ha!). I just looked at the basic GH nute ingredients, and it apparently contains none at all.
 
not a big fan of the silica , i did not see any differences in the plants when i used it and i am a frugal person who believes less is more

i did not see any difference when i snapped off fan leaves , they were not harder or easier to snap off , stems seemed about the same , no extra fiber or nothing i could see with my eyes

and yields were the same

not saying silica doesnt help , i just didnt see any changes
 
Ganjier may be on to something with the silica supplementation. I knew it helps with cell wall strength and thus stem strength but in looking around the whirled wild infernet, I see sites saying it helps prevent fungal infection, increases nutrient uptake and moisture retention(which would explain the plants ‘drinking less’ I think). I think Bubba and pute both use silica supplements but I could be wrong.
Dr Bruce has studied silica and says plants can grow without but adding always increased overall plant health. Thier garden had pm issues and the silica pretty much eradicated it
 
not a big fan of the silica , i did not see any differences in the plants when i used it and i am a frugal person who believes less is more

i did not see any difference when i snapped off fan leaves , they were not harder or easier to snap off , stems seemed about the same , no extra fiber or nothing i could see with my eyes

and yields were the same

not saying silica doesnt help , i just didnt see any changes
Your sandier soils probably have high silica.
 
not a big fan of the silica , i did not see any differences in the plants when i used it and i am a frugal person who believes less is more

i did not see any difference when i snapped off fan leaves , they were not harder or easier to snap off , stems seemed about the same , no extra fiber or nothing i could see with my eyes

and yields were the same

not saying silica doesnt help , i just didnt see any changes
Says the guy who grows in the high desert where I bet the plants get a lot of silica from the desert…😁
 

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