Humidity levels that change dramatically cause harm to the plants

D

DesertSmoke

Active Member
Did a first auto-flower grow on my spare bedroom floor under lights hung off my small 2x4 tent frame. Not a single problem I know of during that cycle. BUT, for Christmas I got a 4x8 Vivosun grow tent and a pair of vs4000 lights. It has a pair of 6-inch exhaust fans plus 2 small clip-on fans to blow on the heat sinks of the lights which does grow very warm when on for long periods.
I have 10 Bubba Kush auto flowers and a tomato plant all in 5 gal bags, (tomato is in a 7-gal bag) AZ allows a total of 12 plants for our household.
Here is my problem. "IF" it is a problem.
Closed up the tent holds an easy 70 plus % humidity when the lights are on and the zippers are zipped. Temps are fluctuating from 63 degrees to 74 degrees with a heater inside. No exhaust fans on. This tent/grow is being done in a screened in back patio.
When I open the tent for watering or any maintenance the humidity drops to 20ish or below depending on the real temps and humid levels outside. Pretty much normal levels for our area
This is all being done in the Yuma Az area where humidity is always low, as in below 30% unless it is monsoon in the summer, or it is actually raining outside. Typical humidity can range from 5% to 25 % during the daytime most of the year again except for the monsoon time frame.
Question is, does this big swing in humidity levels hurt my growth or am I just being a newbie worry wort.?
If it is harmful how do I keep the levels up or down to a specific level? I realize a humidifier will raise the inside the tent numbers but that's not my problem, it is the falling off by 50 or more points almost immediately when the tent is open for more than a couple of minutes.
Lastly, if I turn on a single exhaust fan the levels go down but so does my inside tent temperature. Our desert nights are getting into the high 30s and low 40s at night and mid to upper 70s daytime. I hate to beat up a plant with both humidity levels jumping off the pages and my temps having a wide swing as well.
 
Hi, Desert Smoke-
In my grow space, the exhaust runs for half an hour, then it's off for half an hour- I do this to keep the temps up in there.
When the fans go off, the humidity goes up as high as 70, when they come back on, it drops back to 30 or so- this has gone on 24/7 for 6 months.
The plants don't even notice!
Also the temp is constantly varying- 80f with the fan off, down to 68f with the fan on..
They don't care about that either-
I don't think you'll see any adverse effects.
I don't have a dehumidifier, so I have to grow using the "it is what it is" method 😁
 
The best way to control temperature and humidity in a tent is to have a smart exhaust. It only comes on if the setpoints are reached (ie. humidity > 65%), then turns off. I find this allows me to dial in my humidity and still keep some of the heat from the lights.

The @VIVOSUN AeroZesh with a GrowHub would allow you to control your exhaust with setpoints. It would also allow you to control your VS4000 (both if daisy-chained). You can use the GrowHub to schedule your lights (no more timer), change the intensity, simulate sunrise/sunset and change the spectrum. All from the GrowHub or anywhere using the app.

Also, I recommend a big box/floor fan for your tent. Without this you'll have micro-climates in and around the plants. You want all of the air in your tent to be the same humidity & temperature if you can so you need the air moving around in there. I keep mine blowing diagonally in the tent.

Finally, if you are keeping your tent at the correct temperature & humidity 99% of the time, I wouldn't worry too much about the opening/closing fluctuations. Good luck and Happy Growing.
 
Plants are more interested in your average over time than they are second to second. As long as you are keeping their averages good you’re in good shape. Think about the speed at which a plant moves, grows, signals hormones etc. it’s gonna take a little bit for the plant to even recognize the shift.
 
Back
Top Bottom