We Get Greener Kit Cassingham & her Bigger Half

Lessons From My Greenhouse - Humidity

If you aren't careful, your greenhouse will be green in ways you weren't planning. Moss, mold, and mildew are what I'm talking about, though it's black mold I'm most worried about.

Living in a dry climate I'm not used to thinking about humid conditions. Even when a friend asked me about how I'd vent the greenhouse I didn't understand the importance of her question. I get it now, and am hoping I'm not too late.

Initially I loved stepping into the greenhouse and feeling that hot, humid air. My plants must be loving it, right? I guess they liked it just fine, but the wood of my greenhouse decidedly didn't like it. The door started swelling, making it hard to open and close the door. It got heavy as it got water logged too, causing it to pull at the hinges -- again adding to my challenges with opening and closing it.

I have a fan running during the day to help distribute heat and humidity, but that wasn't really controlling the humidity. The condensation on the windows was telling tales that the wood would start telling soon enough. What else could I do?

During a very brief warm spell this winter I opened the trap door to the turbine vent. When the greenhouse temperatures started dipping into the 40s at night, unlike being warmer when the vent was closed, I realized I couldn't go with that solution.

Even reducing my watering didn't reduce the humidity enough to dry the building out, or stop the condensation. And the plants weren't too happy with that approach either. I couldn't add humidity controlled vents because of the temperatures.It was too cold and snowy to have someone working outside, much less opening the greenhouse to the winter air like that.

It finally occurred to me! A dehumidifier in my little greenhouse would suck out the extra humidity. I'm on week two of using it, and it is extracting water from the air. It's too early to tell whether that's going to be the solution for next winter, though.

Greenhouse Dehumidifier
dehumidifying my greenhouse

The weather is getting milder so I'm able to leave the greenhouse door open a bit during the day. Hopefully that will help the door and wood start drying out. I'm keeping my fingers crossed that the greenhouse doesn't have black mold because the remediation would be costly. Having mold and mildew in the greenhouse doesn't make me happy, but not nearly as unhappy as having black mold.

Being able to air the greenhouse out this summer is an exciting option. The windows, door, and vent will all help dry everything. Until then, I'm hoping my little dehumidifier will do the trick.


I would love to have a greenhouse (or coldframe) so we could keep greens like kale or turnips going all year long. However, I can't even seem to grow greens during the summer, so there's no point trying to tackle the challenges of winter gardening yet! Good luck!

vlnvla at March 21, 2011 6:47 PM


It's definitely a process for me too. I've played with growing plants indoors and out for 40-ish years, and still have a long way to go in mastering the skill. I too want fresh greens in the winter, and have done pretty well. Next year will be even better, I'm sure.

The tomatoes I planted last August are starting to produce. The tomato that was transplanted from my outdoor garden has been putting out tiny tomatoes most of the winter -- what a treat.

More lessons will be shared with time. If I can save others the hassle of learning their own lessons my job is done. :~)


Kit Cassingham at March 26, 2011 4:29 PM
Post a comment

Remember Me?

(you may use HTML tags for style)

Please wait. Your comment is being processed ...