60-70rh when lights out late flower/ripe

Caliber says max rh 67% or 69% and did a lights out test to find RH goes to 60% in ~7 mins. Then it must be dropping to 37% until lights on.

Is the temperary 60-70rh a concern? Vpd is for lights on but just wondering, it is alarming to see as it may be a longer duration than I think. No auto enviorment equipment.

I did some search bar work and found 60% is ok but in late flower it is a concern when lights on. It gets like 70F 37rh night time when settling in. day time 90F 40-50%rh. 82- 85F when cooling things down ambient wise or it already is, but same day time rh 40-50rh.

Dehuey stays at 40rh.

I would be concerned by a big jump in RH like that at lights out.

Some fungi (including botrytis aka bud rot) need liquid water to germinate. And when the temp drops and RH spikes at lights out, it can cause condensation (aka liquid water) to form on and inside the buds, which makes easier for those pathogenic fungi to germinate.

All other things being equal, I would actually consider it more important to have stable humidity than low humidity, i.e. better to be 60% all the time, with good airflow, than 40% most of the time, with a sudden jump to 60% every night.

weedstoner420 said:

I would be concerned by a big jump in RH like that at lights out.

Some fungi (including botrytis aka bud rot) need liquid water to germinate. And when the temp drops and RH spikes at lights out, it can cause condensation (aka liquid water) to form on and inside the buds, which makes easier for those pathogenic fungi to germinate.

All other things being equal, I would actually consider it more important to have stable humidity than low humidity, i.e. better to be 60% all the time, with good airflow, than 40% most of the time, with a sudden jump to 60% every night.

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I had a feeling I wouldn’t be the only one concerned. It is a short 2x2 LED so it swings fast when on or off. I added side lighting which is working so I am keeping it, wonder if delaying that one to shut off last might help. Or turn exaust on high.

I have a legit dehuey but is hard to remember to turn it back up after an hour, and air gets too dry to even live in lol. Lights out at midnight so it is hard to do by hand and was hoping to be done with expenses for a while. Not sure how exaust on a dial would work without turning fan off and on, harming it.

medidedicated said:

I had a feeling I wouldn’t be the only one concerned. It is a short 2x2 LED so it swings fast when on or off. I added side lighting which is working so I am keeping it, wonder if delaying that one to shut off last might help. Or turn exaust on high.

I have a legit dehuey but is hard to remember to turn it back up after an hour, and air gets too dry to even live in lol. Lights out at midnight so it is hard to do by hand and was hoping to be done with expenses for a while. Not sure how exaust on a dial would work without turning fan off and on, harming it.

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I would go with turning the exhaust up myself. Remove the humid air faster and replace with dry air from outside the tent, that way your RH stays more constant

Also more ventilation would help with that temperature differential from day to night (just noticed you said 70F lights on/90F lights off?). That's probably also contributing to the humidity spike - warm air can hold more moisture without it condensing than cool air.

weedstoner420 said:

I would go with turning the exhaust up myself. Remove the humid air faster and replace with dry air from outside the tent, that way your RH stays more constant

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I can supplement heat too, 50w or 200w pointed at the zipper opening, making a 6” open intake. I know this is related to cold temps holding less moisture, raising humidity. That is one advantage of 2x2, it will make it 85-90F easy. Just for an hour.

Was quite a twist to first learn that, everyone I know thinks the opposite. The things growing teaches lol.

also, I need to edit that to make it clear, 70F 37rh night, 85-92F 40-50rh day. Fluctuations from cooling ambient temps down/watering and then ambient temps are 65-85F 40rh.

It has a vortex 4” can fan with filter and speed dial that never goes above medium and already obtains negative air pressure at low. Very high static pressure fan. So I think the issue is that it is one big auto exausting so much moisture, the walls feel sticky.

60-65% at night is fine if you have a lot of air movement. I had a bud start rotting because it was simply laying against the tent wall due to heavy weight. Didn't see it until I rotated the plants as I do every few days. Chopped that part of the bud off and the rest was fine. But you WILL get rot if you don't have airflow and if the buds get fat.

ismann said:

60-65% at night is fine if you have a lot of air movement. I had a bud start rotting because it was simply laying against the tent wall due to heavy weight. Didn't see it until I rotated the plants as I do every few days. Chopped that part of the bud off and the rest was fine. But you WILL get rot if you don't have airflow and if the buds get fat.

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I was not expecting to pack this 2x2 wall to wall and underneath canopy the way I did but it is lol. Plenty of buds touching wall but not the big 2-3 inch chonkers.

Not that big but to have 50+ of them lol. It is a easy level grow strain and buds are 12” but more on the airy side of colas. Not due to stress though.

Seems like the resistant type, yes its packed tight but the fan leaves only make a 6” canopy bush. One fan below and one above. Shaved legs.

I surely enjoyed working with larger space, this was the battle I chose.

I have my dehumidifier coming on 3-4 minutes before the light goes off to avoid precipitation with the temperature drop, your worst humidity isn't too bad, i get through full grows and don't see under 60% fwiw I've not had bud rot in years.

Star Dog said:

I have my dehumidifier coming on 3-4 minutes before the light goes off to avoid precipitation with the temperature drop, your worst humidity isn't too bad, i get through full grows and don't see under 60% fwiw I've not had bud rot in years.

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I think you grow the biggest I seen around here, besides one crazy exception which I know you can match or top. I do not mean to sound like I seen it all but I surf around a lot up til now.

That is great to hear, it is those things that help me feel better about things that can cause concern. Aside from that I think I can correct the drop, I just did not know until now that it was happening.

This is my first true scrog so I was a bit nervous, I am getting real close to chop. Next time will be bigger space, I like to grow the biggest/best that I can in coco and would hate to stunt a plant on purpose just to fit in a space. It becomes a challenge like solo cup or 1x1 IMO.

few weeks ago, but it went through that all flower. Lookin good? I do not see PM or anything. Just an error I made possibly showing a little bit.

medidedicated said:

View attachment 5265015
few weeks ago, but it went through that all flower. Lookin good? I do not see PM or anything. Just an error I made possibly showing a little bit.

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Yeah if that pic was from a few weeks ago, then now is the time to start making sure your humidity and ventilation is on point.

Is it possible to increase either the size or number of intake vents, so you can turn up the exhaust without straining it or stretching the tent too much?

Looking good btw, they're gonna be some spears when they're done...

weedstoner420 said:

Yeah if that pic was from a few weeks ago, then now is the time to start making sure your humidity and ventilation is on point.

Is it possible to increase either the size or number of intake vents, so you can turn up the exhaust without straining it or stretching the tent too much?

Looking good btw, they're gonna be some spears when they're done...

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It has 2 with light baffle and screen which catches dust great and blocks light and they are perpendicular to eachother and the fans above and below the canopy are set in opposite fashion to the intake.

I could up the exaust without tent issues I just wonder if that can dry out the leaves strikingly as technically it barely needs to be exchanged at minimal basis let alone 5x or 10x given it is small. As stated can always open up the zippers by the bottom.

It is customizable but expensive and just want to finish this up and put it away for a minute.

Thanks! Thanks for the tips too, I see people get nervous with 15-20 tops per 4sq ft and this is 50+ in a 2x2.

Hi all. Relative newbie to the forum. Been lurking a while but never thought I had anything useful to add until now.

I was also having issues with swings in temp and rh. Growing indoors in my living space makes it difficult, for me anyway, to control my tent enviro. Then I decided to switch lights to off during day hours and on at night. Now during "day period" my temps are 74-75f and 45-46%rh VPD 1.5-1.6, "night period" 69-70f and 48-50%rh VPD 1.1-1.2. No longer big swing in VPD. I'm in mid to late bloom wk5.

This worked for me. Hope it helps someone else.

Opening a small opening with zippers with cheap heat source blowing into it at safe distance could make it 85-95F in there. Could set it on a timer.

That would allow the space to absorb more of the plant sent humidity/fresh watering for the transition as well as faster air intake. I tested the science a bit and saw for myself that it works. Maybe trial and error the next few days.

medidedicated said:

It has 2 with light baffle and screen which catches dust great and blocks light and they are perpendicular to eachother and the fans above and below the canopy are set in opposite fashion to the intake.

I could up the exaust without tent issues I just wonder if that can dry out the leaves strikingly as technically it barely needs to be exchanged at minimal basis let alone 5x or 10x given it is small. As stated can always open up the zippers by the bottom.

It is customizable but expensive and just want to finish this up and put it away for a minute.

Thanks! Thanks for the tips too, I see people get nervous with 15-20 tops per 4sq ft and this is 50+ in a 2x2.

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The air doesn't necessarily *need* to be exchanged that much, but doing so will help suppress any sudden changes in temp and humidity.

weedstoner420 said:

The air doesn't necessarily *need* to be exchanged that much, but doing so will help suppress any sudden changes in temp and humidity.

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I used a pc fan during veg haha. Got more growth than I can handle. But yes flowering needs extra air which I could still do with pc fans in a 2x2 but need carbon filter.

I tried opening a small intake with the door zippers and turned fan in high, still hit 68rh. I guess I will try heat supplement tonight with fan on high and opened door. the lights only add like 10-15 degrees, the heat supplements can add 20-25F.

I almost asked in a thread for what attributes to rh and how much, like fabric pots for example. Do you think 2x2 would do better with solid plastic pots? Do fabric add 5 or 10%rh? Wondered if anyone knew by messing around with a caliber.

I know it was stated that it will probably be ok. Just bothersome that it happens.

Dang, what is the temp and Rh in the room where the tent is? A 20% humidity spike every night would definitely concern me. Running relatively high RH is fine as long as you have proper ventilation, but mold and PM love big swings in humidity.

Did I read that this is an autoflower? Have you tried just leaving the tent door completely open when you off the lights, to see what happens to the humidity then?