What's more important in the last month of flower, having a vpd between 1.0-1.5 or keeping my humidity in the 40's.

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Perrin6363

Perrin6363

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I can't control the heat as well as I can control the humidity. The heat rides around 72-74. I can get my rh down to 47% but then I'm outside the threshold of 1.5kpa. Just barely outside of it at 1.52. I can let my rh get up to 53-55% and then I'm around 1.3kpa. I've never experienced bud rot and I really don't ever want to so I was keeping rh as low as possible. I can't get the temps any lower except at night and then my rh is around 55%. Which I can't get lower with the lights off. If I have to choose, which is better?
 
growsince79

growsince79

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I can't control the heat as well as I can control the humidity. The heat rides around 72-74. I can get my rh down to 47% but then I'm outside the threshold of 1.5kpa. Just barely outside of it at 1.52. I can let my rh get up to 53-55% and then I'm around 1.3kpa. I've never experienced bud rot and I really don't ever want to so I was keeping rh as low as possible. I can't get the temps any lower except at night and then my rh is around 55%. Which I can't get lower with the lights off. If I have to choose, which is better?
Use a programmable exhaust to control rh and temp.
 
Aqua Man

Aqua Man

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VPD but they coincide… a temp drop is also beneficial.

The issue of bud rot happens wheb the air within a few millimeters of the buds is to humid not because of room RH. This is where air flow is important and the larger the buds the more prone. This is where topping can come in handy for big producers.

Hell you can finish with RH in the 60’s or higher and some do exactly this. The key is the RH right at the surface of the buds so controlling that is your key to avoiding bud rot… not room RH although room RH does have an effect on this.

Keys to watch are air movement, RH spiking just after lights out, avoid spraying at this time (for a few reasons)

Now too low of RH is a much bigger issue than most realize as it can stress a plant and a stressed plant is more prone to an infection.

So i suggest a VPD of around 1.2-1.4 if you can with LEAF temps lower of about 70-72f (under LED likely room temps of 74-77f as leaf temps and room temps are different… if under other lighting let me know)

That will allow anthocyanins to pop and reduce heat degradation of terps and cannabinoids. This should be done the last 2 weeks of flowering.

Prior to that i suggest leaf temps of 75-77f (under LED room temps of around 79-82f) and the sane VPD
 
Perrin6363

Perrin6363

638
143
VPD but they coincide… a temp drop is also beneficial.

The issue of bud rot happens wheb the air within a few millimeters of the buds is to humid not because of room RH. This is where air flow is important and the larger the buds the more prone. This is where topping can come in handy for big producers.

Hell you can finish with RH in the 60’s or higher and some do exactly this. The key is the RH right at the surface of the buds so controlling that is your key to avoiding bud rot… not room RH although room RH does have an effect on this.

Keys to watch are air movement, RH spiking just after lights out, avoid spraying at this time (for a few reasons)

Now too low of RH is a much bigger issue than most realize as it can stress a plant and a stressed plant is more prone to an infection.

So i suggest a VPD of around 1.2-1.4 if you can with LEAF temps lower of about 70-72f (under LED likely room temps of 74-77f as leaf temps and room temps are different… if under other lighting let me know)

That will allow anthocyanins to pop and reduce heat degradation of terps and cannabinoids. This should be done the last 2 weeks of flowering.

Prior to that i suggest leaf temps of 75-77f (under LED room temps of around 79-82f) and the sane VPD
I haven't gotten a thermometer to check leaves yet. I do plan on it but this is my first grow and there's already been so much learning and figuring I just held off on leaf temps. I wasn't even checking vpd until recently. That's really great info. I'm going to go over it again, thanks
 
Aqua Man

Aqua Man

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I haven't gotten a thermometer to check leaves yet. I do plan on it but this is my first grow and there's already been so much learning and figuring I just held off on leaf temps. I wasn't even checking vpd until recently. That's really great info. I'm going to go over it again, thanks
If no IR temp gun and under LED just use the room temps i listed as a guide and try to stay within them. It will likely land you right in the target zone if not cery close to
 
Perrin6363

Perrin6363

638
143
VPD but they coincide… a temp drop is also beneficial.

The issue of bud rot happens wheb the air within a few millimeters of the buds is to humid not because of room RH. This is where air flow is important and the larger the buds the more prone. This is where topping can come in handy for big producers.

Hell you can finish with RH in the 60’s or higher and some do exactly this. The key is the RH right at the surface of the buds so controlling that is your key to avoiding bud rot… not room RH although room RH does have an effect on this.

Keys to watch are air movement, RH spiking just after lights out, avoid spraying at this time (for a few reasons)

Now too low of RH is a much bigger issue than most realize as it can stress a plant and a stressed plant is more prone to an infection.

So i suggest a VPD of around 1.2-1.4 if you can with LEAF temps lower of about 70-72f (under LED likely room temps of 74-77f as leaf temps and room temps are different… if under other lighting let me know)

That will allow anthocyanins to pop and reduce heat degradation of terps and cannabinoids. This should be done the last 2 weeks of flowering.

Prior to that i suggest leaf temps of 75-77f (under LED room temps of around 79-82f) and the sane VPD
After reading again, I bet my leaf temps are right there, bc as you said my room temps are right there and I am using LED. I can't get it any colder in there, I've got my little window ac as low as it'll go. But I bet I'm right there within those thresholds.
 
Aqua Man

Aqua Man

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And an RH around 50% with those temps should put you in a good place. In your situation the best thing you can do is to make sure you have good air movement through the buds… reasonably of course you dont want to windburn them
 
Aqua Man

Aqua Man

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After reading again, I bet my leaf temps are right there, bc as you said my room temps are right there and I am using LED. I can't get it any colder in there, I've got my little window ac as low as it'll go. But I bet I'm right there within those thresholds.
Yeah i looked at your numbers and i didnt see any issue with them the way they sit now
 
L

loveinyourheart

94
18
Well, this is weird. yesterday morning, ive read this thread and took notice about airflow.

Im at day 76, and have one fan just at the pot level. So i went to look for budrot!

low and behold, there was on a couple of my main colas, on two plants out of 4 plants, bud rot that i know for a fact wasnt there yesterday. Ive cut down the two plants and removed budrots affected area.

i probably lost a oz on each plant. its taken me 3 hours to look everything to make sure i didnt miss any more budrot. fml

I now have a fan blowing directly on my two plants in my tent and increased my exhaust fan speed. at around day 60 now, ill always increase air flow and exhaust fan

lesson learn the hard way i guess.
 
Perrin6363

Perrin6363

638
143
Well, this is weird. yesterday morning, ive read this thread and took notice about airflow.

Im at day 76, and have one fan just at the pot level. So i went to look for budrot!

low and behold, there was on a couple of my main colas, on two plants out of 4 plants, bud rot that i know for a fact wasnt there yesterday. Ive cut down the two plants and removed budrots affected area.

i probably lost a oz on each plant. its taken me 3 hours to look everything to make sure i didnt miss any more budrot. fml

I now have a fan blowing directly on my two plants in my tent and increased my exhaust fan speed. at around day 60 now, ill always increase air flow and exhaust fan

lesson learn the hard way i guess.
Dang man I'm sorry. I'm actually running out there right now to check mine. I've always had a fan pointed downwards towards the canopy but recently put one at the bottom pointing up through the plants. I'm super nervous about getting it. So you think it was bad airflow that got you?
 
L

loveinyourheart

94
18
Dang man I'm sorry. I'm actually running out there right now to check mine. I've always had a fan pointed downwards towards the canopy but recently put one at the bottom pointing up through the plants. I'm super nervous about getting it. So you think it was bad airflow that got you?
yeah, its quite brutal As it started on the biggest colas. At least, ive catched it right at the beginning. Had to break down most of the big colas to make sure i got all the bud rut. Major pita
i have colas the size of coke cans.

now my drying will be severely affected as i have to use a fan to make sure it dries slightly faster. So half my harvest is a bit compromised. Will make great edible. My two other plants are looking amazing and ive been inspecting them and no mold

im almost certain the mold issue was cause by poor airflow cause the two mold plants were the furthest from my fan. the fan was really not blowing enough on the colas, only on lower branch. Im positive its poor airflow as logically its what cause bud rot: stagnant humidity around the buds
 
Aqua Man

Aqua Man

26,480
638
yeah, its quite brutal As it started on the biggest colas. At least, ive catched it right at the beginning. Had to break down most of the big colas to make sure i got all the bud rut. Major pita
i have colas the size of coke cans.

now my drying will be severely affected as i have to use a fan to make sure it dries slightly faster. So half my harvest is a bit compromised. Will make great edible. My two other plants are looking amazing and ive been inspecting them and no mold

im almost certain the mold issue was cause by poor airflow cause the two mold plants were the furthest from my fan. the fan was really not blowing enough on the colas, only on lower branch. Im positive its poor airflow as logically its what cause bud rot: stagnant humidity around the buds
Gentle breeze with low temps after 3 days at around 70f 50% RH this dries the surface of the buds then drop temps to low 60’s if possible and bump humidity up to 60ish this slows the dry allowing start chea and chlorophyll to break down for a smoother product.

You sont need a ton of airflow just good air movement around the buds
 
freezeland2

freezeland2

3,421
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I can't control the heat as well as I can control the humidity. The heat rides around 72-74. I can get my rh down to 47% but then I'm outside the threshold of 1.5kpa. Just barely outside of it at 1.52. I can let my rh get up to 53-55% and then I'm around 1.3kpa. I've never experienced bud rot and I really don't ever want to so I was keeping rh as low as possible. I can't get the temps any lower except at night and then my rh is around 55%. Which I can't get lower with the lights off. If I have to choose, which is better?
I push mine very hard in last couple weeks. My rh is in 30’s and vpd of 1.6 - 1.7
 
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