During veg plants like humidity. I usually shoot for 65rh, BUT higher temps, ie 80*f+, you might want to bring up higher, closer to 68-70rh. This is probably why your plants are thirsty more times than not.
A good goal for veg is a vapor pressure deficient or VPD of .9-1.1 w/ 1.0 being the sweet spot.
I’ll try and find some charts to send you for VPD. Does your tent controller tell you VPD? It’s a combination of temp and rh.
For flower you’ll want to push the VPD to 1.2-1.4.
After day 21 of flower I’ll drop my rh to 55.
The lower the humidity the more the plant transpires and drinks.
Could be a cause for some of the issues you’re seeing, brother.
I’m familiar with VPD and have been playing with temperatures a bit to try to find a sweet spot. Seems a balance of running the room AC at the right temperature (whatever that is - usually I have at around 68F - 72F) and then figuring out when to kick on the ducting higher than the lowest setting to get that golden VPD.
I’ll keep dialing!
I have the right tools to try to get the temps right. Humidifier. Dehumidifier. AC. The only real rub is the tent in the closet is going to run hotter than the main two tents based on location (but that’s also going to change with winter). Constant dialing! lol
Thank you for the help — hope to be sharing some flowering pictures in a few months! I figure a few more weeks in veg to let the Maui finish up before I flip.
Oh wow. So, my flower temps hitting up close to 78F right now in the closet is on the border of too hot but okay with lights on. Whereas, the lung room (master bedroom), has been too cold it seems. I think maybe then a little warmer and a better fan to even out the rooms might help?
I think the closet will even out when it gets colder out as I’ll be able to cut off its heat source if needed — or if not needed let it ride.
I bumped the AC up to 75 (er, 74F for now) — so it’ll be a little toasty in my room. Which is fine.
Now what to do about a “cold” room for a cure/dry, lol. Need too many different temperatures!
The problem that can arise with flower temps above 78 is mold growth and terpene loss. Keeping below 78 helps mitigate both.
That said, a sativa won’t have these issues but anything broad leaf or broad leaf dominate is much more prone to mold and mildew.
Lights on in the 4x4! Time for an update on these:
4x GDP (Homegrown Cannabis Co)
2x KSS (Homegrown Cannabis Co)
1x Do Me Fast (JP)
1x TK x GF / BBD (Rhai88)
First are foremost – the temps have gone up all around. I set my AC unit to 74F, which is a little warmer than I want it at just for me, but it’s not terrible. The sacrifices I’ll make for the plants (well – I did bring it down to 72F just now, lol). The tent is getting right up to 78-80F now, and I upped the humidity to 65-70RH.
Almost everything got 1000mL of water. The auto got 500mL. The TKxGF/BBD got 200mL. Some diluted BuildAVeg in with the mix of distilled/spring/tap(sat out for 24hrs) water.
Things aren’t exactly where I want them, but they could be worse! At least they’re not dead – looking forward to the flip in a few weeks or so if that timing seems about right.
Quick morning (noon for the plants) update:
-Raised the lights about 15 clicks (half a foot?)
-Adjusted the humidifier for 70RH and refilled it with a gallon distilled
Not loving a few leaf artifacts but will update soon and time will tell! Nothing drastic but I think between my watering, nutrient application, and lights — these plants have been through it a bit, lol. Poor plants. I love them — I’m just an imperfect parent, even though I try.
The humidifier thinks it’s 90+ RH and in reality it’s 45RH. Futzed with it a bit and think it’s still reading high and thus not running. Will be investigating further when the sun comes up. Might put a second one in the tent as a backup for this reason. Silly technology. I wonder where its sensor is….
It’s a VIVOSUN 2-1 Cool/Warm Mist Humidifer. Nothing too fancy. I don’t use the ionizer or the heater. It’s worked fine until — now.
A quick a dirty fix. Added another one. I’m going to raise up and also take out and clean the one that’s misbehaving. I feel though, it’s the product, sadly. The sensor isn’t very high quality wherever it is. Note the new one in front is…running. The one in back is on, full, and set to the same RH goal (70RH).
Edit: cleaned, drained, and reset the back one. Still not misting as it’s detecting too high RH. Also raised it on another upside-down pot. I guess I’ll see tonight. The other one is cranking.
Would it control power then to the humidifier and I just keep it on max blast 4000? I’m intrigued. I guess the thing would also have to turn on when it gets juice without my input for it to work as well.
With the inkbird you can set what RH% your dehumidifier turns on/of as well as a humidifier.
I have it so my dehumidifier turns on at 51% and shuts off when the tent hits 46%.
May have to toy with it a bit to get things “perfect”.
I just had to change my off setting to 47% because the dehumidifier was running all day trying to drop it that last 1% and it couldnt since the lung room was high rh due to a rainy day so the temps shot up to 89 from it running all day and night. I corrected that by opening the tent and running 2 dehumidifiers in the lung room until lights out.
Also i stopped worrying about rh during veg. I used to try to make sure the vpd shit was proper but now i just make sure temps and rh isnt too high and i send it.
Hey bro just as an FYI before you spend more money: Ive grown many healthy plants from seed to harvest (check my grow diary,) without ever caring about humidity in veg. These plants do fine in lower humidity environments. I’ve never had a humidifier in the grow tent.
I’m not sure the inkbird would help as these humidifiers need you to push the power button after they lose power otherwise they stay off. I also have my dehumidifier always running — but I like the devices accuracy and the concept. I can definitely see uses down the line!
Good to know I shouldn’t overthink the humidity — but I do have a question for those that have run veg without one — what is your ambient RH? Living in the desert here generally things are pretty darn dry.
You have a dehumidifier always running and 2 humidifiers. What is the tent RH with no equipment? Tech is tech. All these sensors and ‘ideal numbers’ come from prohibition. These plants wanna grow. A bad parent doesn’t listen in order to adjust. They just provide and expect results.
I had one humidifier running in the tent. This morning, it stopped running as it read the humidity way too high — so I put the other humidifier I have that wasn’t in use in there so at least one was working.
The dehumidifier I run in the master lung room, not in any tents, so that the overall humidity doesn’t creep up.
With no equipment it could be anywhere from 20-60RH depending on the day.
Lower humidity will typically increase VPD, no? Which in turn will force the plant to work much harder since it will perspire to off set the difference. Couldn’t that cause a good bit of stress on the plant? Or is that wrong?
