What effects do fluctuating humidity have?
 

So I recently got my mini-greenhouse up and running and after messing with it for a day or so I have had to set my humidifier on a clock timer. If I just let it run non-stop the entire enclosure gts totally soaked and the humidity can reach up to 90+%. So I set the timer to go on and off every 15 minutes. So for 15 minutes the humidity is down toward 25% then jumps up to 80% or so. I've recorded a high of 88.2% and a low of 23.6% over night. Now I did have the timer set to have longer gaps of not running at night. Up to 45 minutes being off.
My assumsion is that in a jungle environment the humidity drops at night.

Am I wrong? Will the constant fluctuation cause problems? Is the sky going to fall? Will the other kids laugh at me?

These are just some of the questions I have running wild in my head.

Thanks! ;)

I think you will be okay...remember, in the wild, the humidity is the actual source of "watering" for orchids, since the rain is infrequent and no one is there actually watering them. In your case w/ a mini greenhouse, I would be more concerned that the plants are getting to dry out adequately between waterings with humidity getting that high, as we all know that roots and media that stay too wet can lead to rot. Now, that also depends on what you're growing in there...and are they in pots, or mounted, or what? Is there a fan in the minigreenhouse? That will help a lot...and it will need a little bit of ventilation and fresh air, or else you'll get mold. Its a hard balancing act, but with time and patience, you can get it right...just remember, air movement is key...I'd say humidity is less important than good watering and air movement, IMHO.

Yes there is a fan in the miniGH. And actually through all this the Neostylis, the Brassavola and the phal I have in there, the media is drying out. I had to water the Neo and Brassa this moring. As for fresh air, hmmm... The bottom of the miniGH is open. I am thinking about moving the fan to the bottom and using that opening to draw in fresh air. Thanks for the help.

I wouldn't worry about drawing in more fresh air. A lot of people that grow orchids in terrariums have it completely sealed up just to keep in the humidity. I think that just opening it up to check things out once a day lets in enough fresh air. And I think you are probably getting a lot of air exchange since your humidity drops off so quick. I'm not sure about any negative effects from having the humidity go up and down like that. I wouldn't really think so but I'm not very experienced in that matter. :blushing: I'm sure others will chime in too. Good luck and your new minigreenhouse is looking great! :biggrin:

Actually (wow, my nerdness is really going to show)-- humidity will usually increase at night. Humidity is really governed by the temperature dew-point spread and if the two numbers are 3 to 5 degrees apart from one another, visible moisture will not form (within 3-5 moisture will form). In fact, since you're in Colorado like me, we can have downslope days here on the front range where our temps will spike into the 70's in the dead of winter, meanwhile it'll be dry as anything on those days because the air parcels are squeezing together, forcing them to release heat but the moisture content remains the same-- ergo, much less humidity. Sometimes the temps will be 70F and the dewpoint will be as low as 10F. That means we'd have to chill out down to within 5 degrees of 10F to have visible moisture, such as rain or snow!!! It also means our relative humidity at 70F Dewpoint 10 is roughly 10% or so? So bad for the nasal membranes!

So my point is, often time, especially in our environment, a night time low temp will creep towards our dewpoint and taking in a deep breath via your nose won't induce a bleed-out! in general, a decrease in temps will go closer to the dewpoint and make humidity more apparent.

This is VERY important when flying because as a pilot, I watch that spread and if the spread decreases and is under 32F, icing becomes a definite worry. In terms of orchids, you could get some pretty saturated air and even have it "rain" in your greenhouse.... if your plants collect water, I would fear rot. If it is 90% humidity but dew forms, I would think your aerial roots would be happy-- though fungus becomes an issue.

Did any of that help or did I just bore you to tears?

Ryan, actually it did make sence. Thanks!

I think maybe it did rain in there the other night! Water was all over the floor. The humidity was around 80% or so, but the temp in the basement drops to 60 degrees F at night. That's before I got the humidifier a timer to turn it on and off.

I'm still playing around with the timer and the humidistat on the humidifer. I guess this will have to be one of those kinds of projects. Play, wait and see, then play more, wait and see...

Be wary of the humidistat on the machine as well-- they are notoriously flakey. However, visible moisture would make me agree that 80-90% humidity was definitely present.