VPD vs. humidity?

[Delps8]

Where does the 20% increase come from, your experience or

It was in one of the documents cited by the page on the Pulse site.

from an actual side by side comparison, under controlled conditions?

That's the rub…

I don't have the time to do an experiment - clones + multiple grow environments + temperature control + documenting everything. And then reproducing your findings once you've completed the first round.

That's just a rough outline of what's needed to do something valid. And if you don't get to that level, it's all you have in an anecdote. :-(

Per my other posting, and this sounds a bit off at first, I really don't care whether it's 5%, 0.5% or 20%. To me, keeping VPD in check using automation allows me to "remove those factors from the growing equation". Per the Bugbee "Nine parameters", by paying $120 I will never have to screw with humidity again and I'll have "optimal" VPD.

 

[CaptainLucky]

Im gonna disagree with this kind of.. VPD has been known since at least 1936, here’s a link to the first study:

Google Scholar

scholar.google.com

D. B. Anderson was the original proponent however it never caught on. It has an incredibly accurate link between fire and weather. It serves many great purposes that are poorly understood because as we know, it’s not necessary to understand it to grow. It’s not necessary to understand VPD to know that when it’s dry, fires will start, but it will give you a very pinpoint number at which fire will start. It’s a measurement which needs much more study in relation to our environments and as climate change becomes more serious we will need to understand it better.

Plants can grow in any range of conditions. They can barely survive in poor conditions or thrive in perfect conditions. As the climate in an area changes over time, those plants that are barely surviving will only hold on for so long before they can no longer be grown there. Having VPD helps to tell us which plants should be grown where, at a larger scale. This will become more useful as climates change and the old ways and plants of the area become irrelevant.

However.. for your average home grower.. this isn’t really necessary. VPDs importance is lessened with the smaller and more specific your environment is. You don’t need to know the VPD to grow plants at home, you just need to know your environment. Especially with something like cannabis that performs well in a range of climates.

Those in drier environments have already made their changes or adapted to their environments without needing a measurement. Those in wetter climates have adjusted or adapted without needing a measurement. However, if for some reason you found yourself responsible for deciding what crops or plants to grow over a large area, knowing the average VPD would be a useful resource to determine what would grow best in that area.

It can’t be denied though that unscrupulous capitalists have decided to exploit a not well understood measurement to sell people more crap they don’t need. VPD is more useful from a historical/current perspective than a day to day measurement needed be taken by someone with 4 plants in a 5x5 area

I’m gonna stop here because I’m already rambling and I’m only gonna get worse and I made my point

So what you’re saying then for someone like me in a 4X4 tent it doesn’t matter which is what I thought all along. CL

 

[Delps8]

I think the fact that there is so much debate on the subject demonstrates that is a measurement of questionable value at best. Some folk take a technical view of their grows and good for them

"debate" - I don't consider ignorant whinging a debate.

What a handful of Sage Stoners on some cannabis site probably isn't a valid counter to reproducible science that is easily explained by basic scientific principles.

Really. Check out the seminal papers on this. If you find an issue, good on ya but the last thing I'd do is not follow a technology trend when the totality of the argument against it consists of something typing the word "rubbish".

But you're spot on about people having different levels of tech in their grow. One reason to use machines is to reduce human labour. For $120 I will not have to ever again deal with RH. That's pretty appealing.

Personally, I've never measured anything except ml/L of feed - no ppfd, ec, vpd, par, lux nothing
I used to measure pH but quickly realized that about 3-5ml/L pH down will get me to somewhere around 5.5-6.5 and I'm not too bothered exactly where, and my plants don't give a shit either, as long as they are fed and look happy

Fan, light and stick 'em in a pot of something - I'm not trying to grow specimen spaceships, just a bit of weed for a stash
So call me an amateur - have been for the last 40 years or so

Amateur! ;-)

Not knocking your approach at all. To me, the key question is "Are you getting the results you want?"

I understand not measuring light because cannabis is very bountiful even without high DLI but not measuring pH? Interesting. Cannabis will also grow in a wide range of pH but, if you've been doing it year after year after year, that tells me that you've dialed in your grow over the years and you've got a very stable grow environment. That's great and, yes, I'm envious!

 

[CaptainLucky]

Seriously! Where's that?

"considerably more" - I quoted prices from a delivery service here in SoCal. Their top

[time passes - checks prices again]

Their premium products are >=34% THC (how do they do that?). They have one at $650 per ounce, a couple at $600, and the other half dozen at $500. Wow.

That’s just crazy, they don’t pay that much in Hawaii for Hawaiian I don’t think . But I’m not sure because I never been there but sounded logical. lol CL

 

[Roy Growin]

"debate" - I don't consider ignorant whinging a debate.

What a handful of Sage Stoners on some cannabis site probably isn't a valid counter to reproducible science that is easily explained by basic scientific principles.

Really. Check out the seminal papers on this. If you find an issue, good on ya but the last thing I'd do is not follow a technology trend when the totality of the argument against it consists of something typing the word "rubbish".

But you're spot on about people having different levels of tech in their grow. One reason to use machines is to reduce human labour. For $120 I will not have to ever again deal with RH. That's pretty appealing.

Amateur! ;-)

Not knocking your approach at all. To me, the key question is "Are you getting the results you want?"

I understand not measuring light because cannabis is very bountiful even without high DLI but not measuring pH? Interesting. Cannabis will also grow in a wide range of pH but, if you've been doing it year after year after year, that tells me that you've dialed in your grow over the years and you've got a very stable grow environment. That's great and, yes, I'm envious!

Hehe - no worries dude, we're all on the same page and just growin' some bud, whichever way we choose
Chill

 

[Keffka]

So what you’re saying then for someone like me in a 4X4 tent it doesn’t matter which is what I thought all along. CL

Almost.. Im saying you don’t need it to grow plants successfully, especially in a 4x4. You could benefit from using it, but it’s not a requirement to be successful.

However, if you’re controlling your RH, like running a humidifier, you’re already using it to an extent, you’re just not dialing it in. Similar to how I let my lights heat my room but I’m not obsessively keeping it at steady temps. It would be identical if I didn’t have a thermometer but I suck at telling temps by skin feel so I need a measurement lol.

 

[Roy Growin]

So someone educate me...
If I have a 100w intake fan and a 100w extractor, I have a VPD of zero, right?
Isn't that like outside?

 

[bluter]

But you're spot on about people having different levels of tech in their grow. One reason to use machines is to reduce human labour. For $120 I will not have to ever again deal with RH. That's pretty appealing.

that's always the hope. the problem i have with most automated grow gear is it always works until it doesn't. when it doesn't can be disaster.

i know of at least 2 fires and 3 flood situations due to automated gear. in every instance the growers put too much faith in the systems and decided they didn't need to monitor as closely as they should have.

i don't even trust my timers completely. i've had mechanical timers jam and catch fire. i'm not much more confident in the digital ones.

 

[Keffka]

So someone educate me...
If I have a 100w intake fan and a 100w extractor, I have a VPD of zero, right?
Isn't that like outside?

It’s not about airflow. It’s about how much moisture is in the air which in turn impacts how fast the plant can pump water out of the medium and into the air during transpiration. Knowing the measurement and controlling it basically controls the speed at which the plant works.

For an accurate measurement you would need your room temp, rh, and the leaf surface temperature of your plant

 

[Delps8]

that's always the hope. the problem i have with most automated grow gear is it always works until it doesn't. when it doesn't can be disaster.

Hope? Huh. I don't "hope" shit. It's a piece of mass produced electronics from a reputable manufacturer. Statistically, that product is likely to work for decades. I'm quite confident it will be obsolete long before it fails.

"can be a disaster" - so? "Anything" can turn out to be a disaster. No need to take advantage of anything new but if change wasn't part of life, we would have stopped at the amoeba.

i know of at least 2 fires and 3 flood situations due to automated gear. in every instance the growers put too much faith in the systems and decided they didn't need to monitor as closely as they should have.

Remind me not to hang out with you…bad shit happens!
Bad shit happens all the time. That's not news and it's not hard to figure out what you need to do minimize problems when something fails. In those situations, those folks paid for their negligence.

i don't even trust my timers completely. i've had mechanical timers jam and catch fire. i'm not much more confident in the digital ones.

I used mechanical timers for my first grow, in 2017. We got hit with a power outage and I dicked up resetting the timer. If I remember correctly, it went into something like a random pattern. Dunno. The plant reveged and I never got to harvest.

The bigger picture, I'm thinking, is how we look at growing cannabis. To me, it's a means to an end - I only grow because weed is very expensive in SoCal. I've entertained the idea of moving to Colorado and, if I were to move there, I would have no need to bring my grow equipment.

You seem to be on the other side of the spectrum (no pun intended) - you enjoy the process of growing cannabis. Plus, you're a hands on person - you build grow lights, right? So the tactile sensation and the ability to manipulate something (bend a strut in a light or super crop a stem are very similar actions) are part of what makes you tick. Shit, I like woodwork but spend my workday pushing a mouse and typing on a keyboard. Very different.

Why is that? Even in 2017, I had one humongous plant and one "regular". That started happening when I started growing again in 2021. One plant just dominates the grow. Now, I just grow one plant but I tried everything to figure it out. I changed the location of the air pumps and the location of the hose to and from the water chiller. I've got completely different lights, etc. The tent's the same and it's the same house but I've always had one plant (could be right or left side of the res) grow head and shoulders above the others. Why?

 

[CaptainLucky]

Hehe - no worries dude, we're all on the same page and just growin' some bud, whichever way we choose
Chill

Good tude. CL.

 

[Delps8]

Almost.. Im saying you don’t need it to grow plants successfully, especially in a 4x4. You could benefit from using it, but it’s not a requirement to be successful.

However, if you’re controlling your RH, like running a humidifier, you’re already using it to an extent, you’re just not dialing it in.

And that gets lost in the shuffle.

The AC Infinity humidifier is an excellent product even if it didn't work with the C69. The Controller 69 controls 4 devices and runs over Bluetooth and WiFi so any device attached to it can be controlled from anywhere in the world. So, even if you just want to run your humidifier and your fans, completely forgetting about VPD, it's still a pretty good deal.

Toss in the fact that you can control VPD just by setting it up in the Controller — why not?

 

[bluter]

The Controller 69 controls 4 devices and runs over Bluetooth and WiFi so any device attached to it can be controlled from anywhere in the world. So, even if you just want to run your humidifier and your fans, completely forgetting about VPD, it's still a pretty good deal.

that was the system that burnt down my friends house and grow. he had cameras set up and got to watch it burn in real time from 200km away. it did work great before that.

edit: he actually builds controllers now. i've built some lights for him previous.

 

[Porky82]

This thread is just turning into 1 blokes extreme consumerism and trying to justify it using VPD!

 

[CaptainLucky]

Almost.. Im saying you don’t need it to grow plants successfully, especially in a 4x4. You could benefit from using it, but it’s not a requirement to be successful.

However, if you’re controlling your RH, like running a humidifier, you’re already using it to an extent, you’re just not dialing it in. Similar to how I let my lights heat my room but I’m not obsessively keeping it at steady temps. It would be identical if I didn’t have a thermometer but I suck at telling temps by skin feel so I need a measurement lol.

I’m using a inkbird to keep the temperature and RH in range with my exhaust fans. They work great just set n forget. CL.

 

[bluter]

found out last night it wasn't the controller, he thinks it was a blue lab ph monitor that started the fire. i'm not sure if it was connected or running separate, blue lab has it's own app and could run independent.

was past the point i could edit the original post.

 

[Keffka]

I’m using a inkbird to keep the temperature and RH in range with my exhaust fans. They work great just set n forget. CL.

Funnily enough, that means you’re controlling your VPD even more than I am I’m still doing it manually by adjusting my humidifier level and keeping it within a 10 point range

Every time I’ve gone to buy a controller I get distracted and buy something else.. last time was 20 inch plant elevators and drip trays lol. I’m real good at talking myself out of purchases and into other purchases

 

[CaptainLucky]

Funnily enough, that means you’re controlling your VPD even more than I am I’m still doing it manually by adjusting my humidifier level and keeping it within a 10 point range

Every time I’ve gone to buy a controller I get distracted and buy something else.. last time was 20 inch plant elevators and drip trays lol. I’m real good at talking myself out of purchases and into other purchases

My inkbird was one of the best things I’ve bought for my tent. Takes all the stress away from checking the RH+temperature. CL

 

[CaptainLucky]

a new local has just spent $2600 cdn on a 2x2 and a 3x3 tent and gawd knows what and killed 3 grows straight. he keeps killing seedlings like it was a business. he's not set up quite right and we can't get him to listen.

myself and a friend have been trying to coach him, i want him to join here but he's paranoid, his wife is super sketching, and i think she managed to sink some good decisions.

Why is he paranoid in a country where growing is legal? If he was in Manila I could see it. CL

 

[LukeHighWalker]

Before you buy some fancy gadgets, you should fly over some forums and inform yourself @ some trustful websites. I jumped fight into HPA and knew that's very tricky. Of course, know-how sticks with try and error, but, there is nothing above forums like the ones @ 420 magazine