VPD - following chart and south they go!

[Have2]

Man, what the fuck did we do back in the days when no-one had ever heard of VPD and we had little way of controlling our environment anyway?

And way less hermies back in the days..

 

[Have2]

I appreciate you response and I need to apologize for the tone of my postings. No excuse.

Re. RH 4± - I switched from a Pulse + Inkbirds to AC Infinity and their humidifier. I calibrated using salt but you can also get a Boveda "kit" which consists of one packet and instructions. The Boveda is quicker and reusable.

Water temp changing leaf temp? I could see that being an impact of having a big bucket of water ameliorating temps but, other than that, the two main factors that would drive LST would be ambient temp, IR radiation (very little from LED's), RH, and wind speed. My grow is in a 2' x 4' tent and the res holds 28 gallons so I know if buffers temps for me. In your setup, would you res have enough thermal mass to impact your plants in that way?

Re. VPD being an issue - what I wrote was describing the problem the wrong way. VPD = a combination of RH, and ambient and leaf surface temperatures. I assume that wind speed is assumed to be 0. Given that VPD is just a proxy for, primarily, ambient temp and RH, if your grow isn't doing well in what is considered an optimal range of VPD values, that has nothing to do with VPD. What it means is that your grow isn't growing in what are considered optimal ranges of temp and RH. That's key — VPD is just a way of expressing two numbers (temp and RH) as one number.

If we take the idea of VPD away, the issue is that your grow is not thriving under RH and temp where cannabis is known to thrive. One question to be asked it "Why?" but another, arguably valid question is, "Who cares?". I'm not being facetious, lemme explain.

Metrics are key to reproducibility, with an underlying assumption that reproducibility is, actually, a goal. Unless you're a stickler for detail, as I am, does it matter that this grow/strain isn't growing under what we humans describe as optimal conditions? The plant's happy and, unless you've got to go to extraordinary lengths to keep the plant healthy, then maybe is just the way this grow/strain functions. I'm not advocating "Lie back and think of England.", if you're familiar with that phrase, but, unless there's a need to "fix" this issue, perhaps it's OK to roll with it.

The "If it ain't broke don't fix it." rule be well applied here. Shift the focus from being on VPD to "is the plant healthy". That grates me, personally, because I'm a process-oriented person (software engineer) but, unless this becomes an ongoing issue, how would "Just let it ride." work for you?

Apologies accepted! They are pretty rare here!

I'll answer back to your post later, have some things to do before taking few minutes to answer properly!

 

[Prawn Connery]

Take longer to become a good grower? I mean just looking at the plant you (eventually) learned that they look bad when you're sweating like a pig or it is so humid that you can't concentrate. That is using organoleptic tools for environmental measurement.
Now you can use some sensors and follow directions in a book. That does not help if you don't know how to collect meaningful data (calibration, proper placement) or ignore your plants. But if you lack that skill you will never learn it.

I'm guessing you've never seen land race sativas in SE Asia then? Hot and humid all year round. And yet . . . that's exactly where cannabis evolved!

My point is that not everyone can control their environments to the enth degree and that plants will still grow outside "ideal" VPD parameters. It can also be strain related, as sativas handle hot humid conditions better than indicas that prefer it drier.

So typically I will grow indicas when the weather is drier and sativas when it is more humid.

I also think it's amusing that we're all supposed to be "better" growers with all this new information and yet I see newbies tying themselves in knots over it all the time. Don't get me wrong – of course it's useful information and I'm fully invested in the science – but there are probably a few basics that need to be learnt before going down the rabbit hole.

A little bit of knowledge can be a dangerous thing . . . I know plenty of good growers who have never even heard of VPD. They tend to be a bit older, so obviously experience counts for something.

 

[Prawn Connery]

And way less hermies back in the days..

Yes and no. I've noticed the prevalence of hermies in a lot of modern strains. Pretty much everything I have grown in recent years that had cookies genetics was pre-disposed to hermaphrodism (to varying degrees).

But there were also hermies back in the day. Especially strains derived from Thai genetics. Thais and to a lesser degree hazes (which also had Thai genetics) were notorious for it.

 

[curious2garden]

I know plenty of good growers who have never even heard of VPD

I grew outside the VPD for years. Living in the Mojave Desert the price of environmental control was simply more than I was willing to pay. During the high heat of summer I'd just shut down my lights when my canopy hit 105.

My cannabis tasted good, got me high and relieved my husband's pain. That was the point of my growing and it worked. The two marked differences from my out of wack Summer grows and my in VPD Winter grows, was Winter plants had a nicer appearance and yielded slightly more.

 

[Prawn Connery]

I grew outside the VPD for years. Living in the Mojave Desert the price of environmental control was simply more than I was willing to pay. During the high heat of summer I'd just shut down my lights when my canopy hit 105.

My cannabis tasted good, got me high and relieved my husband's pain. That was the point of my growing and it worked. The two marked differences from my out of wack Summer grows and my in VPD Winter grows, was Winter plants had a nicer appearance and yielded slightly more.

Case in point. I didn't even shut down when it got to over 40C and I was growing under HPS. Lots of air flow, lower the EC and hang on!

But you're also right that the quality would vary at different times of year. The same plants would stretch when it was hot and slow down a little when it was cold and – if you weren't careful – get mouldy when it was humid. So you learn to run different strains at different times of year and manage the environment as best you can.

 

[Lou66]

Sure it's a weed and grows pretty much everywhere. I didn't want to imply you are wrong, just that some newbies can use that information and get to the finish line in fewer tries.

Cannabis is an easy plant.

 

[Prawn Connery]

I know. And all I was trying to say is you have to learn to walk before you can run. Sometimes too much information before you understand the basics can be detrimental.

 

[Charles U Farley]

Man, what the fuck did we do back in the days when no-one had ever heard of VPD and we had little way of controlling our environment anyway?

We did it back then just like I'm doing it now, by observing and reading the plant instead of doing eleventy million fucking scientific calculations and measurements.

Some of us even had the foresight to develop cannabis that would adapt and thrive in various and adverse environmental conditions, instead of trying to create an ideal and perfect environment, thereby transforming cannabis into some delicate, fragile plant that needs a perfect environment just to exist.

Btw, I respect your knowledge of lighting.

 

[Have2]

Yes and no. I've noticed the prevalence of hermies in a lot of modern strains. Pretty much everything I have grown in recent years that had cookies genetics was pre-disposed to hermaphrodism (to varying degrees).

But there were also hermies back in the day. Especially strains derived from Thai genetics. Thais and to a lesser degree hazes (which also had Thai genetics) were notorious for it.

Yeah but barely all new gens have cookie in it, that is sad!

 

[Have2]

I appreciate you response and I need to apologize for the tone of my postings. No excuse.

Re. RH 4± - I switched from a Pulse + Inkbirds to AC Infinity and their humidifier. I calibrated using salt but you can also get a Boveda "kit" which consists of one packet and instructions. The Boveda is quicker and reusable.

Water temp changing leaf temp? I could see that being an impact of having a big bucket of water ameliorating temps but, other than that, the two main factors that would drive LST would be ambient temp, IR radiation (very little from LED's), RH, and wind speed. My grow is in a 2' x 4' tent and the res holds 28 gallons so I know if buffers temps for me. In your setup, would you res have enough thermal mass to impact your plants in that way?

Re. VPD being an issue - what I wrote was describing the problem the wrong way. VPD = a combination of RH, and ambient and leaf surface temperatures. I assume that wind speed is assumed to be 0. Given that VPD is just a proxy for, primarily, ambient temp and RH, if your grow isn't doing well in what is considered an optimal range of VPD values, that has nothing to do with VPD. What it means is that your grow isn't growing in what are considered optimal ranges of temp and RH. That's key — VPD is just a way of expressing two numbers (temp and RH) as one number.

If we take the idea of VPD away, the issue is that your grow is not thriving under RH and temp where cannabis is known to thrive. One question to be asked it "Why?" but another, arguably valid question is, "Who cares?". I'm not being facetious, lemme explain.

Metrics are key to reproducibility, with an underlying assumption that reproducibility is, actually, a goal. Unless you're a stickler for detail, as I am, does it matter that this grow/strain isn't growing under what we humans describe as optimal conditions? The plant's happy and, unless you've got to go to extraordinary lengths to keep the plant healthy, then maybe is just the way this grow/strain functions. I'm not advocating "Lie back and think of England.", if you're familiar with that phrase, but, unless there's a need to "fix" this issue, perhaps it's OK to roll with it.

The "If it ain't broke don't fix it." rule be well applied here. Shift the focus from being on VPD to "is the plant healthy". That grates me, personally, because I'm a process-oriented person (software engineer) but, unless this becomes an ongoing issue, how would "Just let it ride." work for you?

Nice thinking about the boveda! I think I have few left, I'll be able to compare both.

That is fantastic how we can actually see how much water holds air at different temperature... I was calibrating the sensor and at the end of the cycle a perfectly correlated of the humidity vs temp! As for the water temp, I'm in RDWC, differential temp is 3F, and I spent few hours measuring the leaf temp vs water temp vs ambient temp... If plants drink water at 66-68, I guess it's not instant that is reaching a higher temperature. Maybe I did something wrong but found a correlation.

"Re. VPD being an issue - what I wrote was describing the problem the wrong way. VPD = a combination of RH, and ambient and leaf surface temperatures. I assume that wind speed is assumed to be 0. Given that VPD is just a proxy for, primarily, ambient temp and RH, if your grow isn't doing well in what is considered an optimal range of VPD values, that has nothing to do with VPD. What it means is that your grow isn't growing in what are considered optimal ranges of temp and RH. That's key — VPD is just a way of expressing two numbers (temp and RH) as one number."

That's what I think... Not all plants needs X humidity/light... Some plants will die if they directly under the sun!

I am too, adopting a if it's not broken, why fix it... But I do love to play around! Always saying to myself, what if I could improve a bit again? It's a therapy itself playing with the plants!


Sorry for late reply, some health issues and well, I tend to disappear for few days when it happens!