Humidity

[CattyRobb]

So I finally got a good humidifier (ultrasonic cool mist) and it has me wondering: How do you change the humidity where you grow? Do you even mess about with it at all, in your conditions? I’d be interested to hear your responses. I grow indoors in a fairly small room with decent natural light supplemented with a couple of light rigs.
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[Mike H]

I don't need to worry about it since moving to the greenhouse, BUT, when I grew in the window I had trays and saucers of water on the shelves and a humidistat to monitor things and did notice a 10 point or more rise. Grouping plants also helped as well.
Physics tells us that if there is no air movement, evaporating water molecules will "sink" so putting the trays on a high shelf should be beneficial ( theory only).
Let us know if you notice an improvement with the mister, lots of growers swear by them I've read.

[Sheryl]

I live in Florida with plenty of natural humidity and grow outdoors. I can't add anything constructive. Sounds like you're set up pretty good now!

[CattyRobb]

So far not much difference on medium mist but I’ll leave it on that setting overnight. If no different by morning I’ll try it on the strongest setting.
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[raybark]

If the room is open to the rest of the house, you're humidifying the entire house. Nature hates a gradient so the water molecules will rapidly spread out to fill the available volume. You may have to provide a barrier (close the door) to slow that leakage.

[Chris in Hamilton]

If the room is open to the rest of the house, you're humidifying the entire house. Nature hates a gradient so the water molecules will rapidly spread out to fill the available volume. You may have to provide a barrier (close the door) to slow that leakage.

or your curtains will rot, you'll have mold behind anything (furniture, paintings) against the walls or inside closets. Even algae growing on windows. Then you'll have to spend a whole pile of money on renovations

[Mike H]

Sounds like advice from past experience Chris
While we are talking algae...I'm growing in a new greenhouse, does it make any sense to spray everything now with a coating of Physan 20 as a preventative?
My gut tells me this would be a waste but perhaps someone has experimented with the idea.

[CattyRobb]

Yeah I know Ray. It’s half blocked right now and it probably won’t help much in summer because it gets so hot if I close it off completely. I will see what I can accomplish tweaking other variables as well. The plants were all doing ok at 50% but the roots were not nearly so happy as in summer when it was running 60-65 on average. There was also a little leaf desiccation on my smaller plants initially. I’m using a space heater in there now to keep everyone happy. I can close it off completely until the hot weather sets in.

Chris, I’m not shooting for more than 60-65. Hope that won’t cause me to get any ick. Temps at 70/65 day/night.
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[Dorsetman]

Here in UK the natural humidity is about 60% for much of the time ( in my garden) and hence tends to besimilar in the greenhouse. But that is too low. 70% is better. So, in a <50 sq metres greenhouse I have two humidifiers, both on separate humidistats, and set to thatl level. In the summer I have to top up their supply tanks - they need RO water- every couple of days , but now, in mid winter, they come on only occasionally.

It seems to me that too low humidity stresses the plants, but too high humidity gives too much encouragement to moulds , rots and fungi - especially if there is insufficient or even no air movement. But I have three 48 inch sweep fans running non-stop. Which seems to give me good results and avoid problems.

[Mike H]

Looking at my gauges it's 79% humidity in my greenhouse with no assistance and 60% outside at 5 PM (snow storm approaching any minute it's normally lower in the winter)
In my house it's 38%.