Humidity at night?

[addictedcountryman]

Is it okay to let the humidity level drop at night? Like to 30%?

[greenbean]

I would think so. It's cooler and dark, so high humidity is not a must. Too much humidity at night can lead to disease because the plants don't dry off properly. But I'm pretty inexperienced, so I could be wrong.

[magicatt]

I agree. I got funky white mold on my medium and had to use alcohol to get rid of it. I think it will be alright.

[cloudswinger]

30% is pretty low for orchids. There's usually a drop in humidity in the evenings, but not generally that low. Somewhere semi-tropical like Florida goes from 80% to about 60%, the tropics from 90% to 70%. I'd try to maintain at least 40%

[addictedcountryman]

Thanks for the advice everyone. I am just concerned because I get paranoid about leaving things plugged in when I leave.

[Ray]

Why is the humidity going down at night? Cooler air can hold less water, so the relative humidity should go up with a constant moisture supply.

If you think about it, that's why there is dew in the morning - the air cooled so much at night that the absolute humidity exceeded 100% relative humidity, so the excess "fell out" of the air as liquid.

[Ross]

Originally Posted by Ray

Why is the humidity going down at night? Cooler air can hold less water, so the relative humidity should go up with a constant moisture supply.

If you think about it, that's why there is dew in the morning - the air cooled so much at night that the absolute humidity exceeded 100% relative humidity, so the excess "fell out" of the air as liquid.

That's also why California firefighters hope for cooling at night to raise the humidity so they can get control of the firelines.

[Kona's Gold]

Here in Hawaii at a elevation of 1450ft the humidity goes up at night from around 60-75% in the day to 80-95% at night. Temps range from 76-85F days and 62-67F nights.The orichids in my shade house are doing just fine. So I would chime in with Ray and say 30% is too low keep it up to at least 40%.

Roland

[EdinAZ]

Originally Posted by Kona's Gold

Here in Hawaii at a elevation of 1450ft the humidity goes up at night from around 60-75% in the day to 80-95% at night. Temps range from 76-85F days and 62-67F nights.The orichids in my shade house are doing just fine. So I would chime in with Ray and say 30% is too low keep it up to at least 40%.

Roland

I agree with you and Ray. I grow in a greenhouse, and my temps and rh are spot on with yours. My Orchids like it like that!

Perhaps she is talking about windowsill (or other set-up) growing in a home. Humidity is A LOT harder to control there. Up until about 7 years ago I was a "house grower", and I could really never get my plants' environment humid enough to suit me (OR them).

Ed

[Leisurely]

Roland, we experience about the same humidity change in Florida as you do in Hawaii.

I don't think I would be concerned about 30% humidity at night though. Granted, it is a little too low but the plants are going to be less subject to getting fungal problems from high night time humidity. Lower night time humidity is what we try to obtain. If the day time humidity is adequate, the only problem I can see is that more watering might be required.