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This is a Cold Frame

03.16.11

I’ve been talking about cold frames a lot over the past months, and invariably get ‘what’s a cold frame‘. This is a cold frame. It’s a piece of Dutch geniusness. And I find it slightly embarrassing that we, living up here in Edmonton, are not friends with it, nevermind masters of its use. Its purpose is to prolong growing seasons – something you think we’d value. It’s a mini-greenhouse, of sorts, that is easily built, portable, and reasonably accessible to all.

The temperatures in a cold frame will get vastly hotter than the ambient outdoor temperature. For actual research and good building ideas, read Elliot Coleman’s books – worth the time anyway if you have the slightest interest in gardening. This, my friends, is my ticket to extending garden harvest into late Nov, early Dec – and even more importantly, to bridging ‘the spring gap’. These awkward coming months where the root cellar veg is dwindling in quantity and quality, but the garden isn’t yet producing.

So now that you’ve met my cold frames, I welcome you to check in through the year to see what I can get away with via their use. Last year, last garden harvest before heavy snow was mid-Nov. I intend on an early Dec harvest this year. And normally the first spring greens are at an edible size May long weekend. I intend on that first harvest to now be the first or second week of April. Can it really be done?!!?

The econ: greenhouse plexi to do about 4-5 cold frames, 2 layers of plexi per ‘light’ thick = $25. Thanks Kijiji. Old storm windows are also a cheap and easy route. Dimensional lumber for 2 coldframes 8′ long = ~$35. Eating garden veg year-round = priceless. Time investment = 1 afternoon.

11 Responses

  1. Kirsten says:

    You didn’t mention, and I couldn’t tell from the photos, but did you hinge it on the back? My dad mentioned that he uses a special temperature sensitive hinge (he might have gotten it from Lee Valley Tools) that raises and lowers the lid depending on how hot or cold the interior gets. Also, are you going to insulate the cold frames?

    ps LOVE Elliot Coleman! I think he needs to be essential reading if you’re going to try growing food in a short growing season.

  2. Kevin says:

    Kirsten – nope. The plexi is so light that I can grab the 2×2 ‘handles’ [that also help frame the light structure] and pull them off easily. One day, I very well may end up getting self-opening-hinge – those things are cool indeed. Insulate. Interesting. Haven’t read about doing that yet. In the fall that’d be easy – I could just pile leaves around the sides. And I’ve considered having a couple sheets of thin plywood on hand to throw atop the frame in the event of a forecast for heavy snow or severe cold.

    Glad to hear of another Coleman follower!

  3. Wooden cold frames are more effective in insulation than metal ones. FSC oak cold frames are excellent for the job.

  4. Kirsten says:

    Leaves would be a great (free) insulate as long as you didn’t get too much wind. My parents used to use straw bales stacked around their cold frames (they’re fans of Coleman too!).

  5. Evelyn says:

    Every year I plan on making some cold frames but never get to it. How are you using them? Early greens? Or do you harden things off in them?

  6. I have a brick planter and found some glass panes when I moved into my house. Did the cold frame idea with it and had lettuce way ahead of everyone else. I, too, am very surprised this is not used more often in our climate.

  7. Judy Z. says:

    I think cold frames are a great idea too as I am most motivated to start planting in about February when I have had enough of winter already and want to see green growing things.
    I wonder if you put a reflective surface like mylar on the back wall of the cold frame to incerase the light plants receive if it would keep plants growing longer. Adding some kind of mass either along the walls or the front to absorb heat would facilitate earlier and later growing and moderate temperatures. You could use some of those extra bricks that you have from your mega oven. I haven’t seen them lately but there are mylar things you can get that are intended for the back of camping chairs to reflect the heat from the fire onto your backside. My sister says they work really well. It is thick (maybe 8 or 10 ml) so would last many seasons. I once had a sign advertising some kind of beer that was heavy mylar and shiny on the back. I keep kicking myself but I don’t think I kept it when I moved. It would be great for the reflector to improve light conditions in early spring and late fall. I think in summer it would be a mistake to use reflector as would act like solar oven and cook your plants. I wonder if you could use the basis of a solar oven with lots of mass on base and sides to store heat (probably plus superinsulated) for overnight with the auto opener to prevent overheating on sunny winter days…

    Have your tried hot beds in your cold frames? I think in France they used to dig pits, put in a genorous portion of fresh horse manure and cover with soil (? how much?). They used the hot beds to grow cucumbers as they like warm soil and need lots of nutrients. The manure heats up as it composts to warm the bed. This may have been in a greenhouse but I think the book I read said they provided cucumbers in December.

  8. Judy Z. says:

    PS. I was just looking back over your “From The Garden” entries and came across the Belgian endive segment. Did they sprout and did you enjoy them? We only saw the roots not the results.

  9. WOw. Reading the comments was as interesting as the post. My grandmother used to use cold frames, but I didn’t know what they were called. I thought she was just using old windows to catch the sun in her garden. I was just a kid. That was that. I have never seen, nor heard of them since. I wonder if one of the reasons is that for quite some time, so few people gardened at all. Just like everyone used to know how to sew, and now hardly anyone does as you can buy clothes far cheaper made from another country than you can buy fabric here and make it yourself. Basically, the same thing has happened with our food… except that has greater far reaching effects.
    I have always had a garden, but didn’t always own the space I gardened. I have always loved gardening and never thought about elongating the growing season. I am so motivated now, but only have 2 mouths to feed. Yet, I am still going to do what I can do. I am so impressed with the reading you do and the learning you share and the truck load of common sense you have that I am edified daily whenever I stop by your site, Kevin.
    :)
    Valerie

  10. [...] so happy to see an earth worm. For the past couple weeks, I’ve been wondering whether or not my cold frames were actually achieving anything. I had considered whether or not I was simply containing the [...]

  11. [...] For anyone interested in more information on cold frames, Kevin Kossowan provides some great info here and [...]

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