whitewidow2
Well-Known Member
Hi, with all this talk of day time temps. - what are the ideal night temps both for veg and humidity Thanks
Humidity should be kept in the same ideal range, day and night, depending on the phase of growth. For veg growth the important thing to understand is vapor pressure deficit or VDP. Basically the weight of the water in the air affects a plants abity to transpire or breath . Higher humidity means more weight in the air that the plant has to push against to transpire. Lower humidity is less resistance and the plant can basically breath easier. In veg a smaller plant with a small root system and smaller total leaf surface area can't transpire as much as a larger plant so a somewhat higher humidity is better. As the vegging plant gets bigger the ideal humidity gets a lower. You don't have to get too carried away with keeping humidity exactly perfect, especially in veg. The best thing is to keep the humidity toward the drier side of the ideal range, at least for established plants, because the better they can transpire the more water they can uptake which will translate to faster growth if everything else is dialed in. For flowering plants keeping toward the drier end of the range is crucial for preventing mold but it can also increase resin production making for more cannabinoids and terpenes.Is there any way I can revive this thread? I'm new to growing and I see you've posted this a long time ago, is there anyway some one could tell me how important night time temps and humidity are? Especially during seedling to veg!
Thank you so much
https://www.maximumyield.com/definition/3142/daynight-differential-difWhy drop temps at all? Would it not be better to maintain the same temps and keep VPD at the same number, lights on, lights off? What is the advantage of lowering temps?
Humidity is relative (HR). It isn't the actual amount of water in the air that affects the plants but it's ratio to the temp or HR. As far as VPD I did say that isn't so important that you follow it strictly but that if you want to understand how humidity affects the plants studying VDP is where it's at.I was referring to following the VPD and trying to keep a spread, just seems like a whole pile of headaches lol. I only lower temps for the simple reason that it cost more to heat at lights out so I drop the temps, the humidity rises but I'm not to concerned as moisture content stays pretty much the same.
I realize it is a percentage of the amount of moisture that the air is able to hold at that temp, note I said moisture content stays pretty much the same. That is why I think it may be better to actually keep temps and humidity the same and actually follow VPD. I have studied VPD and draw my conclusions from that.Humidity is relative (HR). It isn't the actual amount of water in the air that affects the plants but it's ratio to the temp or HR. As far as VPD I did say that isn't so important that you follow it strictly but that if you want to understand how humidity affects the plants studying VDP is where it's at.
I let my room get down to mid 60's with out a noticeable slowdown but I don't let it get much below 65 then the heater comes on . I keep res temps at 66-67 as well. My canopy temps are 75-78 lights on and humidity is kept at 45-55 at all times using intake to dry and humidifier to add back. I have also allowed humidity to get pretty high in flower at times and never had mould or PM inside. Good air flow I think is the key to that .Okay so me for example, where I live it's getting real cold. I'm on my second grow at day 34 of flower, room temps are getting down to low 60s with rh of right around 30s. I currently don't have a space heater either, how much of a big deal is it for temps to be dropping to low 60s?
If it's a pretty big deal I can go buy one, I'm just wondering, is it really that big of a deal?
Yeah my highs get into the upper 70s during lights on.I let my room get down to mid 60's with out a noticeable slowdown but I don't let it get much below 65 then the heater comes on . I keep res temps at 66-67 as well. My canopy temps are 75-78 lights on and humidity is kept at 45-55 at all times using intake to dry and humidifier to add back. I have also allowed humidity to get pretty high in flower at times and never had mould or PM inside. Good air flow I think is the key to that .
I misunderstood. Your comment about the headaches made me think you were leaning the other way. Look into temperature differential. It affects growth in important ways.I realize it is a percentage of the amount of moisture that the air is able to hold at that temp, note I said moisture content stays pretty much the same. That is why I think it may be better to actually keep temps and humidity the same and actually follow VPD. I have studied VPD and draw my conclusions from that.