How to build a cold frame

violetta48March 14, 2010


Can anyone refer me to some idiot-proof "How-to" instructions for building a cold frame? I want to use an old storm door for the top and I'm not the handiest person with tools.

I've surfed the internet and found lots of helter-skelter plans, several without an angled window (which does not give me much confidence in the project), Does anyone know of a classic description on the web or elsewhere?

Many thanks, Vi

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eaglesgarden(6b - se PA)

The easiest way I could suggest doing it is this:

Measure the storm door you plan to use as your "light".

Next you will want to form a box that is exactly that dimension. For example:

If the door is 30 inches wide and 70 inches long, that is the size of the box you will want for the box.

Get a 1 x 12, (for a stronger box, a 2 x 12) that is 70 inches long. (This will be the "back" of the frame)

Next, get a 1 x 8, (2 x 8 if you prefer stronger), that is also 70 inches long. (This will be the front).

Now, for the sides, get 2 2" x 12" boards that are 30 inches long. Cut them along a diagonal from 8 inches on one end, to the corner, so that it is 8 inches in front and 12 inches in the back.

Now, assemble the pieces. Drill pilot holes and screw the end pieces onto the front and back.

Finally, flip the whole thing over, so that the new top is completely flush (this was the part that was on the ground previously). Now, place the storm door over the top, and screw the hinges onto the back. This will allow for easy lifting. You can then look into adding features like hooks to keep it closed in high wind, various different propping devices....a simple 2x2 with some notches cut out for the various heights you want it to be propped open, etc. You could even put some automatic vents on the sides, as a fail safe for over heating.

This method will make a box that has a slight forward "tilt" to it, but will actually provide better tracking of sunlight in the late autumn-early spring.

Check out the 12 season gardener by Jeff Ashton or Winter Gardening by Eliot Coleman. These are great resources. I forget which one recommends the style I just went through, but they have nice pictures and easy to follow instructions. Both should be available at your local library.

    Bookmark   March 14, 2010 at 11:26PM
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Dan Staley

Depends upon what you want to use it for. If you are going all winter, the shorter the front wall the better off you are, as the shadow cast by the front wall means little or no growth there. My front wall is 5 3/4" and I get spotty germination about 10-12" in to the center. Arugula is OK, maché not.


    Bookmark   March 15, 2010 at 5:54AM
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eaglesgarden(6b - se PA)


Can you give a little more information about the mache? What is not OK about it? Germination? Growth? Is it transplantable?

I plan to grow some to overwinter this coming fall, and any information you can offer would be greatly appreciated.

    Bookmark   March 15, 2010 at 7:41AM
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Years ago I built a 8'x20' cold frame at the north end of my garden. I used 2x4s at 4' o.c. sharpened to a point on one end and driven into the ground. I used a 2x6 ridge and hung 2x4 "rafters" at 45 degrees off it. At the bottom, I nailed The rafter to the top of the stake I had previously driven into the ground. I then throw a sheet of polyethylene over the frame and weight it at the bottom with soil and rocks.

The disadvantage is that I am not able to rotate crops (unless I moved the cold frame each spring).

I live at 7400' in SW Colorado and without this, I could not raise peppers or tomatoes. My last frost is usually in mid to late June. I am able to plant tomatoes, peppers , and a zucchini hill within the cold frame on May 1 with harvest beginning in June.

I've set 5 gallon buckets of water at the back to provide a bit of thermal storage. I've had many nights into the low 20's without frost damage.

I pull off the plastic around July 1. It's important to open each end during hot days, though.

Works well for me in a place that is difficult, at best for gardening.


    Bookmark   March 15, 2010 at 10:32AM
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Dan Staley

Eagles, maché here seems to be a little picky for me - it is a very cool season, but for me likes warm soil to germinate and get up there, then after that all is fine. When I sow in coldframe, the soil in the shade barely gets above ~48ºF in the shadow (~9C) so spotty germination. Arugula doesn't seem to mind, and we tried spinach 'Bordeaux' for the first time outside, in the front spotty germination as well, 'Harmony' in the back just fine.



    Bookmark   March 15, 2010 at 3:02PM
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This is so helpful!!!

Many, many thanks. Vi

    Bookmark   March 15, 2010 at 7:33PM
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