Nick Hardy's Skunk Works #3 5x5 - Dissertation Grow

[NickHardy]

I suspected as much, which is why I asked for clarification. Thank you.

Yes. My system is designed to work best when grow room -- an old coal bin -- is between 13º and 18º C. That is max flowering time for me, with no risk of bud rot. I actually insulate the inside of my boxes with Reflectix, and heat the interior with seedling mats and the lights in the tent. Temp is also controlled by vent speed. Flower months occur December, January, March, and maybe April. At that time I have my vegetable gardens, bird and butterfly gardens, and my orchard to tend to.


MGM

13c ha - this is our flower room which is doing double duty as a drying room this cycle, even with no living plants int here that’s a low as we can get it, maybe a bit lower, actually but 19c and 59% hanging for 2 weeks is pretty much perfect.

But with transpiration and 20 plants in full flower we really struggle to get there.

The big dehumidifier and the electric winches for the lights are in the void space above the ceiling

 

[greenmobster440]

Awesome grow space. I love seeing folks setups. I think my favorite was some guy in a cave growing his ass off in Tennessee.

 

[NickHardy]

Stage #1 Pop’em 27th October
Stage #2 Peat to sprout 29th October
Stage #3 Seedling Swicks 2nd November
Stage #4 Veg Pots 14th November
Stage #5 Top 2nd December

So topped. We don’t look at node number particularly. We’re looking to see 4 good branches coming out close together. Like this:

I was quite aggressive, some very nice clones to be had but no room at the Inn. Besides growing from seed makes timing so much easier.

They were hand watered. The solenoid on the pump finally gave up. Sparkey has a new one but its raining and a forty-45 minute motorbike ride so he’s coming tomorrow. In either a coincidence or pumps really don’t like electrical spikes the main house pump has also gone down, no running water. Going to ask about compensation from the Electrical Authority. Our bill is lower recently but its still $800USD a month and the delivery is rubbish. More stable though, no more flickering lights.

My finger slipped and I put my phone in Portrait mode with natural light. I need this for normal zoom sizes. Green is correct.

Nick & Co

 

[Jon]

Stage #1 Pop’em 27th October
Stage #2 Peat to sprout 29th October
Stage #3 Seedling Swicks 2nd November
Stage #4 Veg Pots 14th November
Stage #5 Top 2nd December

So topped. We don’t look at node number particularly. We’re looking to see 4 good branches coming out close together. Like this:

I was quite aggressive, some very nice clones to be had but no room at the Inn. Besides growing from seed makes timing so much easier.

They were hand watered. The solenoid on the pump finally gave up. Sparkey has a new one but its raining and a forty-45 minute motorbike ride so he’s coming tomorrow. In either a coincidence or pumps really don’t like electrical spikes the main house pump has also gone down, no running water. Going to ask about compensation from the Electrical Authority. Our bill is lower recently but its still $800USD a month and the delivery is rubbish. More stable though, no more flickering lights.

My finger slipped and I put my phone in Portrait mode with natural light. I need this for normal zoom sizes. Green is correct.

Nick & Co

Gorgeous. Way to fill ‘er up!

 

[InTheShed]

Hey Nick, since you were most involved in the VPD discussion with Gee over in Jon's thread, I thought I'd put this here.

So light is the driver behind leaf temp, not air temperatures.

Just because I was curious (since I don't control or measure or know much about VPD), I thought I would run a leaf temp test. I tried to make it as accurate as I could but this was not done in a lab!

First I checked the air temp in the tent after the flap had been open for about 10 minutes, fans were on and airflow was good.

20231202_110822 tent temp.jpg

• InTheShed
• Dec 2, 2023

My light was set at 12" above the soil:

20231202_110901 12 inches from the soil.jpg

• InTheShed
• Dec 2, 2023

Leaf temp was 66.7ºF:

20231202_110943 12 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

Then I lowered the light to 10" above the soil (17% closer):

20231202_115050 10 inches from soil.jpg

• InTheShed
• Dec 2, 2023

I waited a while, came back, and rechecked the tent temp:

20231202_120942 tent temp the same.jpg

• InTheShed
• Dec 2, 2023

Leaf temp remained at 66.7ºF:

20231202_120958 10 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

And just to account for any heat coming off the driver, my driver remained fixed in space as it's disconnected from the light and hanging from a heavy gauge wire:

20231202_115111 driver position fixed.jpg

• InTheShed
• Dec 2, 2023

I closed up the tent, and 15 minutes later the air temp had gone up a degree, as had the leaf temp.

My lights are cool to the touch if that matters.

I'd love someone to repeat this in their tent to see if the results are the same!

 

[NickHardy]

Hey Nick, since you were most involved in the VPD discussion with Gee over in Jon's thread, I thought I'd put this here.


Just because I was curious (since I don't control or measure or know much about VPD), I thought I would run a leaf temp test. I tried to make it as accurate as I could but this was not done in a lab!

First I checked the air temp in the tent after the flap had been open for about 10 minutes, fans were on and airflow was good.

20231202_110822 tent temp.jpg

• InTheShed
• Dec 2, 2023

My light was set at 12" above the soil:

20231202_110901 12 inches from the soil.jpg

• InTheShed
• Dec 2, 2023

Leaf temp was 66.7ºF:

20231202_110943 12 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

Then I lowered the light to 10" above the soil (17% closer):

20231202_115050 10 inches from soil.jpg

• InTheShed
• Dec 2, 2023

I waited a while, came back, and rechecked the tent temp:

20231202_120942 tent temp the same.jpg

• InTheShed
• Dec 2, 2023

Leaf temp remained at 66.7ºF:

20231202_120958 10 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

And just to account for any heat coming off the driver, my driver remained fixed space as it's disconnected from the light and hanging from a heavy gauge wire:

20231202_115111 driver position fixed.jpg

• InTheShed
• Dec 2, 2023

I closed up the tent, and 15 minutes later the air temp had gone up a degree, as had the leaf temp.

My lights are air temp to the touch if that matters.

I'd love someone to repeat this in their tent to see if the results are the same!

I’ll do the same. Thanks. Shame I didn’t have the IR Sensor when I had the HPS up.

 

[Greenvein]

Hey Nick, since you were most involved in the VPD discussion with Gee over in Jon's thread, I thought I'd put this here.


Just because I was curious (since I don't control or measure or know much about VPD), I thought I would run a leaf temp test. I tried to make it as accurate as I could but this was not done in a lab!

First I checked the air temp in the tent after the flap had been open for about 10 minutes, fans were on and airflow was good.

20231202_110822 tent temp.jpg

• InTheShed
• Dec 2, 2023

My light was set at 12" above the soil:

20231202_110901 12 inches from the soil.jpg

• InTheShed
• Dec 2, 2023

Leaf temp was 66.7ºF:

20231202_110943 12 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

Then I lowered the light to 10" above the soil (17% closer):

20231202_115050 10 inches from soil.jpg

• InTheShed
• Dec 2, 2023

I waited a while, came back, and rechecked the tent temp:

20231202_120942 tent temp the same.jpg

• InTheShed
• Dec 2, 2023

Leaf temp remained at 66.7ºF:

20231202_120958 10 inches from soil, leaf temp 66.7ºF.jpg

• InTheShed
• Dec 2, 2023

And just to account for any heat coming off the driver, my driver remained fixed in space as it's disconnected from the light and hanging from a heavy gauge wire:

20231202_115111 driver position fixed.jpg

• InTheShed
• Dec 2, 2023

I closed up the tent, and 15 minutes later the air temp had gone up a degree, as had the leaf temp.

My lights are cool to the touch if that matters.

I'd love someone to repeat this in their tent to see if the results are the same!

It's the same here & under led but I think hps/CFL would be different. I just offset my stats to match my leaf temps and roll with it. It's not perfect over time but it seems to work ok

 

[Gee64]

Shed I'm glad your checking this out.

You're VPD is 0.3. Thats a bit too low. The plant wants you to keep moving the light closer until it's leaf temps are 2 degrees less than ambient. Your light isn't close enough to be "in the ballpark".

If you move it incrementally closer until the leaf is only 2 degrees different, your VPD would be 0.4, which is marginally low for that stage, but getting into the ballpark.

Then as you raise room temps and bring the humidity down, your VPD will climb, and you may have to start raising your light.

Grab a VPD calculator.

Here are a few different scenarios, but 1st lets assume you get the light hung where it gives a 2 degree difference, because thats what the plant wants, and that 2 degree difference is after the lights have been on for at least 9 hours.

Always try to find the max VPD value. Plants rev up as the day wears on.

If you set VPD in the morning, the plant will go higher than what you planned later on in the day, so if you are pushing them, use a later reading or you will over-rev them. I can't stress this part enough. It's important. Hermies suck.

So heres the scenarios.

Your current VPD.

What it would be if you moved your light in closer to get a 2 degree difference. Too low for that plant still.

Even higher with a 2% drop in RH. Almost where that plant should be for it's size.

A huge riise in room temp gives a small amount of extra VPD, That plant would love this.

But this is way cheaper and even better.

And this is where the plant is going.

There are lots of ways to make it work, and it works most efficiently at a 2 degree difference. The plant will raise or lower its leaf temp to adjust as the daily needs fluctuate, to vary VPD itself, but can only properly compensate if you are in the 2 degree ballpark. It doesn't like to shiver and it doesn't want a sunburn, it wants nice. 2 degrees is nice.

Also remember that light intensity, being 1/3 of VPD, directly effects stomata and stomata regulate CO2 intake, so if VPD is off, so is CO2 intake.

2 degrees, its an evaporation physics thing that optimizes rate of transpiration.

So if your lights run 12/12 from 6am to 6pm, take your VPD readings at 430 pm.

Don't worry about morning readings, they will be all over the place. The plant is switching gears from lights out respiration to lights on transpiration. It takes awhile to get things photosynthesizing properly.

It's the max reading that you should worry about. After an afternoon VPD check, make your adjustments and live with them for 24 hours until you check again.

Is the light still 10 inches away? What is leaf temp now? If it's still 10" away, check it again in 24 hours.

It usually takes about a week to first dial a plant in. The pendulum swings slowly on 24 hour adjustments. Once you get everything in the ballpark it gets easy to maintain.

I find that after getting the light adjusted, controlling RH is the most effective way to adjust your VPD. But if you live in a really humid area, adjusting heat may work better.

So Jon in Florida is hot and humid, Me in a Canadian desert is cool and dry. Check this out.

Jon in muggy Florida....

Me in the cool dry desert.

Our very different climates can be controlled 2 very different ways, to make the plant equally content.

Be careful, getting too close to the light to quickly will permanently damage leaves.

The higher the VPD, the faster you move water. The faster you move water, the muggier the tent gets. The muggier the tent the more airflow you need. Raising VPD without proper venting can invite both PM and bud rot.

You will know the moment you enter the ballpark, and the moment you exit it, your water consumption doesn't lie. If they start drinking less for no reason, your VPD likely dropped, if they are going dry really fast, your VPD likely spiked.

I don't open the tent without my IR gun in hand, but all readings are purely observational except 430pm. Thats the one I go by.

 

[InTheShed]

You're VPD is 0.3. Thats a bit too low.

Whoa Gee! That was a lot of work to help someone with absolutely no environmental controls other than an oil heater in the room (otherwise it would be a daytime high of 64º in there!).

I'm not aiming to hit any VPD numbers as I mentioned at the top of my post. I usually grow outside during the day (really hard to control VPD and leaf temps in the, I dunno, 90s? Sunny side pot temps at 121º), and inside at night, with the temps and RH being whatever they are. These two autos I'm going to veg inside-only (after transplant out of solos) to see if that helps them stay out of flower until they're bigger than my autos used to be (I quit growing autos for that reason).

The plant wants you to keep moving the light closer until it's leaf temps are 2 degrees less than ambient. Your light isn't close enough to be "in the ballpark".

If I move that light until some theoretical increase in leaf temp (though they don't seem related given the results of my experiment), the leaves would be dead from light (not heat) burn. They didn't like 10" so I backed the light up to 12" again (again with no change in leaf temps).

Other than using a light that puts out heat (like HPS), I don't see LEDs increasing leaf temps with decreasing distance. I'll run this experiment again as they grow, but I would encourage others to run the same drill and see if they get the same results.

 

[InTheShed]

Some research info I found to see if what I was seeing matched what others have found:

"LED grow lights typically have only a small fraction of their emission in the IR portion of the spectrum, so they do not increase leaf surface temperature like HPS."
Source (includes a VPD chart)

"We performed an experiment comparing plant leaf surface temperatures under 8 equivalent LED, MH, HPS and fluorescent grow lighting fixtures in two different ambient air temperatures. Our results show that LED grow lights with a plant-optimized spectrum don't heat plants' leaves like every other form of artificial light we tested."
Source

"Very typical for a flower room, for instance, to be at 75 degrees. In an LED lit room, you've got much less infrared radiation, not none, but much less of it. And so that means that your leaf surface temperature isn't getting as warm from the lights. And even more than that, as natural by-product transpiration, that leaf surface is actually cooling off through evaporative cooling.

"In order to achieve, again, an efficient facility, you need to raise your air temperature in order to raise your leaf surface temperature, in order to maintain your yields or that growth curve that you're expecting."
Source

 

[Gee64]

Whoa Gee! That was a lot of work to help someone with absolutely no environmental controls other than an oil heater in the room (otherwise it would be a daytime high of 64º in there!).

I'm not aiming to hit any VPD numbers as I mentioned at the top of my post. I usually grow outside during the day (really hard to control VPD and leaf temps in the, I dunno, 90s? Sunny side pot temps at 121º), and inside at night, with the temps and RH being whatever they are. These two autos I'm going to veg inside-only (after transplant out of solos) to see if that helps them stay out of flower until they're bigger than my autos used to be (I quit growing autos for that reason).

If I move that light until some theoretical increase in leaf temp (though they don't seem related given the results of my experiment), the leaves would be dead from light (not heat) burn. They didn't like 10" so I backed the light up to 12" again (again with no change in leaf temps).

Other than using a light that puts out heat (like HPS), I don't see LEDs increasing leaf temps with decreasing distance. I'll run this experiment again as they grow, but I would encourage others to run the same drill and see if they get the same results.

Like I said, be careful. But yes, moving your LED will change your leaf temps, it's a test I have run hundreds of times.

Raise your light and see what happens. Maybe your IR gun is out? Have you tested 2 light heights 24 hours apart, after at least 9 hours of steady environment each?

 

[InTheShed]

Like I said, be careful. But yes, moving your LED will change your leaf temps, it's a test I have run hundreds of times.

I did move the LED, 17%, and it didn't change leaf temps. The research I found backs that up rather than supporting your tests, though obviously different environments.

Raise your light and see what happens.

I did!

Maybe your IR gun is out? Have you tested 2 light heights 24 hours apart, after at least 9 hours of steady environment each?

Maybe, but I don't have the kind of steady environment that would enable me to do what you ask. Anyway, I can't believe it takes 9 hours to change a leaf's temperature in response to its environment. My leaf temp went up within 15 minutes of the tent temp increasing.

 

[NickHardy]

"LED grow lights typically have only a small fraction of their emission in the IR portion of the spectrum, so they do not increase leaf surface temperature like HPS."
Source (includes a VPD chart)

This. Its so noticeable coming from HPS to LED in a similarly sized tent (HPS was 4x4, 1000w LED is in a 5x5)

During the day with HPS i was running the AC at full blast set to 16c - I was able to get to 24-25c BUT Rh was absolutely slayed way down at 45% the radiant heat of the HPS was crazy

Here they are at 24c and 25c - btw 2 degrees offset it generally held to be in C not F

1.4-1.5 in Flower is considered excellent so I did all right there. That light would start burning the hairs off my hand at 4”. It was extremely hot so the moisture in the air just got burnt off.

Now with LED I’m running the AC at 28c targeting 31-33c like this, we’re still in Veg so after more like 0.9-1.2 VPD.

These are typical late morning to mid evening -

I’ll do a Shed type test in a moment - I’ll turn up the 3500k light by 20% with 30% UV as well for two hours and see what it does for leaf temp.

My hypothesis is it will do exactly FA.

I’d like to add - I didn’t buy this for VPD, it was to back check my Skin And Eyes (TM) and see how close I could get. The light meter was actually useful sort of for this grow as the light is a commercial model. It comes with no guidance at all on hanging heights, intensity at different stages of grow any of that. With the three dimmers I thought it would be interesting to see where I get to. Same VPD - its just Temp and Rh I factor in. Turns out I get pretty close to decent VPD (and therefore have been the last year because nothing has changed here compared to other grows)

Modern LEDs just don’t alter your leaf temp is my contention, and even then you can move your leaf offset 3 degrees celsius before it really makes a meaningful difference to VPD. It really is a secondary or tertiary element to VPD.

Nick

 

[NickHardy]

30.3c and 806PPFD

I bumped the lights to 880PPFD

I’ll take a leaf temp reading in two hours, won’t be making any changes the environment in that time.

Nick

 

[NickHardy]

and it works most efficiently at a 2 degree difference.

Do you have a source for this - I’ve never read you’re trying to target a specific leaf offset difference. More efficient for whom? You in dry Canada or me in as hot and humid AF?

 

[NickHardy]

Ceteris Paribus

After 2 hours with 84 more PPFD, 10% extra at about 10” 0.1c change.

These are the before and after all data points.

The Rh has climbed reducing VPD - the impact of PPFD is zero with modern day full spectrum LED lights was/is my contention and I’m sticking with it.

I’m now fitting the Dehumidifier to that was delivered 5 minutes after that test started. Been itching for it for days

We’re gonna defol tomorrow and flip on Wednesday I think so time to get the Rh under control.

Nick & Co

 

[Gee64]

Ceteris Paribus

After 2 hours with 84 more PPFD, 10% extra at about 10” 0.1c change.

These are the before and after all data points.

The Rh has climbed reducing VPD - the impact of PPFD is zero with modern day full spectrum LED lights was/is my contention and I’m sticking with it.

I’m now fitting the Dehumidifier to that was delivered 5 minutes after that test started. Been itching for it for days

We’re gonna defol tomorrow and flip on Wednesday I think so time to get the Rh under control.

Nick & Co

2 hours won't give you a proper reading lol, and time of day in the plants world also has an effect. You need to monitor the highest VPD value of the day, make note of the time, make changes, then check 24 hours later to see the changes.

At least you are putting the proper data in now to get a proper VPD reading.

I really doubt that your Pulse Pro instructions are wrong though. They tell you about light hanging height and leaf temps.

 

[NickHardy]

You get that is actually the only bit of data I need to put in? I can go back by the minute for three months. I don’t have these wild fluctuations you’re taking about. I see it on a graph generated in real time and saved for years.

Despite two tests to the contrary, despite me saying my VPD is stable through the day, despite Shed finding literature LEDs don’t impact it - you’re still convinced?

Someone opens the carport doors and parks one the motor bikes I can detect fluctuations in Temp and Rh - some micro degree change in leaf temperatures only measurable after 24 hours? Give me a break.

The lights have <1% impact on my VPD, I’ve been watching it daily under high end lights for 6 weeks. No calculations required. I’m over even discussing the impact of my run ultra cool LEDs and their impact on VPD. It is a tertiary/micro impact, why would you bother and not just spend time on getting the two basics right? Any discussion of it should be qualified with “under HPS or CMH…” IMO.

To be honest I don’t give a toss about VPD, I just care about growing healthy plants that test good, as of ten minutes ago we passed 25lbs since January so I’m probably doing OK with my humble Temp and Rh measurements just as I am.

Cheers.

 

[Gee64]

You get that is actually the only bit of data I need to put in? I can go back by the minute for three months. I don’t have these wild fluctuations you’re taking about. I see it on a graph generated in real time and saved for years.

Despite two tests to the contrary, despite me saying my VPD is stable through the day, despite Shed finding literature LEDs don’t impact it - you’re still convinced?

Someone opens the carport doors and parks one the motor bikes I can detect fluctuations in Temp and Rh - some micro degree change in leaf temperatures only measurable after 24 hours? Give me a break.

The lights have <1% impact on my VPD, I’ve been watching it daily under high end lights for 6 weeks. No calculations required. I’m over even discussing the impact of my run ultra cool LEDs and their impact on VPD. It is a tertiary/micro impact, why would you bother and not just spend time on getting the two basics right? Any discussion of it should be qualified with “under HPS or CMH…” IMO.

To be honest I don’t give a toss about VPD, I just care about growing healthy plants that test good, as of ten minutes ago we passed 25lbs since January so I’m probably doing OK with my humble Temp and Rh measurements just as I am.

Cheers.

Easy buddy, all I'm saying is you didn't have your inputs correct earlier, and now you do, and that both your and Sheds "tests" won't give you correct data.

Now your offset is correct and you know your VPD.

I watch you grow, I know you know how to do it. Most good growers manage VPD without realizing they are doing it. I also know that the VPD that you 1st displayed was wrong, just at a glance, and it turns out I was right.

But you know what, next time I see an error on your part I will let it remain wrong.

And to be fair, you tossed the instructions into the mix that state the exact same thing.

Sorry Nick, I wasn't saying your an idiot, I was saying you were not inputting data correctly. My bad. Carry on. I'm out.

 

[NickHardy]

Huh?! Wasn’t meant like you seem to have taken it at all. Sorry for any misunderstanding. I just think that the changes you’re suggesting a so tiny simply opening the door once a day wipes out any meaningful impact they might have.

For me PPFD for VPD is like changing the type of paint on a sports field looking for a marginal gain in performance.

Leaf temp a 2c input change brought my readings down by about 0.2 - as I said elsewhere over s 1.3 reading when you asked what it told me I said “its a bit high” turns out that was actually 1.1 so it was sweet.

As I said its not something I’m bothered about or chasing.

Sorry for any confusion as to how you interpreted my response.

Nick