Optimum temperature and humidity

Careful following random Leaf VPD charts. You need to know your ‘leaf temperature offset’ so you can pick the right Leaf VPD chart. That chart is a zero-offset chart & would be about 1.0 kpa higher than my real ‘Leaf VPD’ numbers. I would need something like a -10f chart to see real numbers.

Leaf temperature - Air temperature = Leaf temperature offset

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@PhotoFinisH Thank you for clarification… The formula asks for leaf temperature… So i always forget that most charts use offset rather than the actual temperature.

@JOKERSTR Again there are many out there… The best are excel sheets that you enter information and it automatically creates a custom heat map chart for you.

The first one is 2 months old the other three are one month old



Sorry it took me so long to put these up but apparently I used up my replies

@Fiefie my first photos i had in veg for around 20 or so weeks. I started veg with photos and threw in some autos a little while later. Instead of flipping 12/12 i kept everything at 18/6 until the autos were done then flipped to flower. When they were harvested they were nearly 5 ft tall and 4 ft in diameter. I learned my lesson. These girls are about 4 ft tall and different diameters.


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@Fiefie my first photos i had in veg for around 20 or so weeks. I started veg with photos and threw in some autos a little while later. Instead of flipping 12/12 i kept everything at 18/6 until the autos were done then flipped to flower. When they were harvested they were nearly 5 ft tall and 4 ft in diameter. I learned my lesson. These girls are about 4 ft tall and different diameters.


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Well it’s not “rather than”. Each chart uses one offset which should be matched to the offset of the actual leaf temp & air temp.

@PhotoFinisH Offset… Actual…comes up with the same thing… Air temp 79, leaf temp 77…or offset 2.

Here’s the formula:

Not sure what you are referring to.

‘Leaf temperature offset’ using those numbers would be -2 temp units. You must subtract the air temp from the leaf temp to get the leaf temperature offset. 77 - 79 = -2

Tmi. I’m just a guy with a tent in his attic as far as charts and math goes I’m not going to be doing any of that but I do appreciate your intense dedication I was just a little worried about my humidity level being low but I’m not anymore thanks everyone🙂

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@JOKERSTR your welcome… Just trying to get you info. Hope it helps.

Your funny.

Sometimes I even make myself laugh LOL all kidding aside I really do appreciate the help I used to be that guy but I’m retired now and just growing cuz my insurance won’t cover the only medication that gives me any relief so now I’m the guy that makes his own my next problem to solve is Nats or whatever those little bugs are that live in my dirt they don’t seem to bother the plants but they sure bother me I heard about mixing dish soap with cooking oil but that sounds a little weird to me I’m thinking about just spraying the dirt with raid and shaking the pot

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@JOKERSTR those are fungus knats more than likely. What type of medium are you growing in? Ive had success with mosquito bits soaked in water for about 8 hours and watered directly into the soil. I also use DE ( diatomaceous earth ) on top of the soil to get rid of the adults. Also try to allow your medium to dry out real good the first few inches before watering. The larvae live in moist soil and allowing a little longer drying out will help.

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@JOKERSTR You can also add hydrogen peroxide… Breaks down the insects cell walls… Then the peroxide breaks down in O2 and water.

You can also use those sticky yellow sheets. Hang them all over.

But mainly as @ChittyChittyBangin said… Once you get the activity of watering down correctly… You’ll have less pests in general.

Try waiting for the soil to dry a bit before watering/feeding.

@JOKERSTR I started growing for the same reason… Docs kept pushing opioids even though they didn’t work on me. Reefer has truly improved my quality of life… Except the stress of it being illegal… But no one knows I grow except my wife… So it’s not too bad.

I hope you have a great day!

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@Fiefie same. No one knows but family. They reap the rewards also.

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It’s weird how that works doctors tell me opioids won’t work on my pain but it does so they won’t give them to me and I don’t really care for them anyhow but Granddaddy Purple sure helps and I have a friend that I rent a room to she’s a great person but she has a habit of voicing every conscious thought which is a liability so I’m pretty sure all my Neighbors Know but they’re all pretty cool people and I don’t have people running in and out trying to buy weed all the time cuz it’s mine all mine LOL

yeunz all have a great day too

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If you tell me the air temp is 79 & the leaf temp is 77 & you think the offset is 2, then I have to wonder.

My question for the OPs original question would have been: “What’s your leaf temperature?”

I am done with this.

I corrected my statement, provided info… You continue to nitpick symantecs about -2 or 2 when it is obvious there is a difference of 2… Which could be expressed as -2. However… If your going to measure your leaf temp, rather than pick a random “offset” then you’ll have to measure multiple leaves and get an average… The more leaves tested the more accurate. Then why not use you leaf temp you worked for it.

However, before I learned and got a laser temp meter… I used random vpd charts and did fine… Which is what I offered. While explaining there are many others… Which a person will learn… In time.

I will not argue with you anymore… When all I did was attempt to help someone who desired direction.

Thank you for trolling the discussion and turning a positive into something else.

I’m not trying to troll your conversation or play gotcha. Why not add an explanation of the offset & how to get it? That would cover everyone. If I use the 0f offset chart you posted, The numbers on the chart show much different leaf vpd values than mine really are, because my offset is usually around -10f, & not 0f.

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