Pimp My Cold Frame

While the climate here in Los Angeles is exceedingly mild–it rarely gets much below freezing–springtime can, some years, be too cold to get good germination of summer vegetables such as tomatoes and peppers. This was the case in 2010 when I was not able to get a single tomato seed to germinate until late May. To head off another seedling crisis I built a simple cold frame.

In order to prevent the cold frame from becoming a solar cooker (it can get over 80°F during the day this time of year) I pimped it out with an Univent Automatic Greenhouse Vent Opener. The Univent uses no electricity. As the temperature gets hotter a small piston thingy forces open the window you attach the Univent too. As the temperature cools in the evening, the Univent closes the window. It was easy to install, though the directions it came with seem to have been translated back and forth between several European languages before materializing into English.

The price on Amazon seems a bit steep at $50. I got mine on sale from Peaceful Valley Farm and Garden Supply, but they no longer seem to carry it back in stock here.

I’m fully aware that my cold frame, with it’s plastic cover, would be way too flimsy for places with real weather. Nevertheless, I can imagine the automatic vent opener being useful in many climates.

ETA: Mrs. Homegrown here: I just wanted to add a clarifying note. This cold frame is The Germinator ™, one of our recent garden improvements. Ordinarily it is covered with wire screen, which lets sun in but keeps critters out. Erik’s plan is to swap out the plastic sheeting with the wire screen as needed.

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  1. I bought an old window from the Rebuilding Center in north Portland (Mississippi Ave) to use for a cold frame, and now I’m afraid to put it together because I’m afraid of tripping and falling into it and bleeding to death because it’s made from way old glass. So I’ll probably use it in the chicken coop, once I get around to building one.

    But having a device on your cold frame that makes it so you don’t have to keep running out there to open or close it is way cool. I wouldn’t give up on Peaceful Valley- it might be in the big catalog.

  2. I put in my first cold frame this year! I got two double-paned glass doors at the “swap shack.” Nice and thick for our cold climate. Planted kale. It came up. Alas, there’s now 2 feet of snow on top of the frames. I guess around here my cold frames are useful only in early spring to start my lettuces!
    Terry at hencam.com

  3. Have the automatic window opener on my (yes I’m spoiled) greenhouse. It works so well ordered another for the back window. Daytime temps, even in the winter, can get over 100 and I’m always forgetting to open (and then close) that back window. Had to play with it a bit. Seems it doesn’t work as well on a vertical window as it does on a horizontal one.

  4. $50 was a decent price for the opener as I’ve seen it advertised for much higher.
    Of course having an automatic cold frame opener means that you won’t have the true gardening experience of stubbing your toes as you run out to the garden in your pajamas to manually close the frame.

  5. Thanks Mr. Homegrown! Let us know if you’re up here in the Grass Valley area. We’d love to meet you. Peaceful Valley

  6. How easy is it to plant and weed in the coldframe? We recently built one, but have the top in 3 completely removable pieces.

    Pros: Very easy access.

    Cons: Venting can be an issue.

    Of course, some of my plant-frying adventures this spring could be as simple as learning experiences. We may have just been keeping plants in there too late in the growing season.

  7. @Sarah: Sorry, but we don’t have any experience planting in cold frames–we only use ours as a place to start seeds and nurse seedlings.

    Re: your plant frying problem–the automatic venting system Erik put on our frame might help you.

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