Humidity vs VDP
- Thread starter Forsure
- Start date
FirstCavApache64
Well-Known Member
If you control the environment properly you can run most strains in the ideal VPD range throughout flower. I will go with lower humidity and sacrifice VPD some depending on how worried I am about things like bud rot or PM. I can run 45% humidity which is plenty low for almost every strain I want to grow and still be in the VPD range. Having good airflow is important too.
Forsure
Well-Known Member
Thanks for your reply, I have just increased my grow space from tent space to a room and it's pretty full I'm maintaining good VDP but my humidity is around 60% and just going into the second week of flower. It's the bud rot threat and PM I'm a little concerned about.
FirstCavApache64
Well-Known Member
I'd want to work that down with a dehumidifier or more exhaust if it's possible. Doing a defoliation of the lower canopy can help regulate the high humidity a little bit too. 60% is not terrible, but I like to be below 55% and then I drop it as I get to the later stages of flower. Congrats on the bigger space.
Forsure
Well-Known Member
Yeah I have a dehumidifier(not a commercial one though) and just brought a new AC Infinity exhaust fan which is great. I was running 2 tents 1.2m x 2.4m previously in the room I've converted but the bigger space needs a few more adjustments. Thanks for the congrats I am quite excited but don't want to screw it up, brought in Ethos genetics for the new space and they are loving the new space by the look of them but don't want to be complacent.
FirstCavApache64
Well-Known Member
I've never run them but I've seen some really nice flower from Ethos. I have pre 98 bubba kush from clone and a Steve Lemme OG x White Cherry Truffle cross I'm running from a small breeder called GuamMaineian Gardens. I'm about 5 weeks in flower roughly using a new light I got to test out from Cultiuanna. Here's a shot of my 4x4 tent. Hope your grow does really well in the new space. I really need to get a bigger tent so I have to admit I'm pretty jealous.
FirstCavApache64
Well-Known Member
It's my first run with these and they're knock offs. I got them for like 6 bucks a piece and I like them a lot for the drainage but fungus gnats love the holes on the sides. I ran out of Gnatrol and had an explosion of gnats and now I'm waiting for some to get here. That will knock it out but they love these pots. The down side to these knock off ones is they have built in feet that get in the way of most of the support systems I like to use. I'd like them a lot more without the feet. I'll make a decision on them when I see the rootball after chop. If it's significantly better than the fabric pots or smooth plastic I'll learn to live with the feet.
Forsure
Well-Known Member
An inch of washed sand(sand you buy for kids sandpits) on top of your medium will keep them under control, Ive gone 100% hydro straight clay balls for the first time but had used coco for quite a few years before making the switch. Had a issue with gnats and this remedied them really well, their life cycle they burrow into your medium to lay their eggs and then die and when the eggs hatch they come to the surface and the sand works like glass to them and cut them to bits putting an end to their life cycle. So then I just start using it as a preventative measure and never had an issue with them again works well.
FirstCavApache64
Well-Known Member
The Gnatrol stuff works great, I just ran out and got lazy. I bought some earth worm castings and figured I'd have enough beneficials to keep them in check until I bought more. We live out in the mountains and gnats are everywhere because of the woods and the creeks. The sand sounds great but I top dress with organics so I need all the room I can get at the top of the pot for amendments and worm castings. Sounds like it works like diatamaceous earth sort of.
Dirt_McGirrt
Well-Known Member
Mosquito bits work well. Nematodes. DE. Fungus gnats are easy. I just got done dealing with root aphids and thrips and I think I have PTSD.
TCH
Well-Known Member
So when you run that low of humidity, what temp are you running at to keep VPD in check?
GreenHopper
Member
I am not going to pretend i know something because i dont. But what would be interesting is Wetbulb temperature vs VDP as from what little i know they are more closely related to total heat. Sensible temperature temperature and RH is what determines Wet bulb temperature.
Looking at the VDP chart same variables are used to plot out VDP.
Same could be said with Enthalphy (total heat) vs VDP which again is using same variables. same principles should apply to all some what equally as greater difference = greater transfer rate.
Take what i say with a grain of salt other than it appears the same variables are being used and transfer rates appear to apply to all somewhat equally.
Meaning greater the difference the greater the transfer rate.
Dirt_McGirrt
Well-Known Member
Take heat gun reading of the leaf temp, too. Not the tent temp.
Forsure
Well-Known Member
I'm not in a tent anymore have a expanded into a room with more plants and the extra transpiration is making it difficult to get humidity below 60% the leaf temp is usually 2-3 degress lower than the room temperature but my concern is I'm in week 2 of flower if I don't get the humidity down to at least 50% I'll run the risk of PM and bud rot which I don't want to happen as I have just brought some Ethos genetics and it's not quite legal in my country.
DoubleAtotheRON
Well-Known Member
Looking good man!
Spindle818
Well-Known Member
If you have good air movement 55-60% relative humidity should not be a problem. I follow vpd closely until about day 50.
TCH
Well-Known Member
And then? Drop the humidity and throw vpd out the window?
jcdws602
Well-Known Member
Like stated before good air movement is key. I follow vpd throughout the entire grow. I run mid seventies beginning of flower and slowly taper down to 55%-60% towards the end but for the most part of flower I’m in the 60s and 70s. Thinking about it I’m probably safer than others because I live in a desert where pm is not a big concern.