31 March 2009

Turn your freezers into cold-frames

Ever since we ditched our fridge and freezer for food preservation, we have found some excellent uses for the well insulated and sealed boxes. See last December's post on our Freezer Incubator and Brooder, along with some other ideas. This spring, we are testing them out as cold frames for some early greens. The sealed lids are a bonus for this time of year, when the snow is blowing, we can seal them up out of the cold wind.
First we built a false-bottom, 7 inches from the top. We left 4 inches for soil and 3 inches for growing room. The soil will settle a bit, but we didn't want to put the plants too far below the lip otherwise they would get shaded out too much in the morning and afternoon. This one is intended for mesculn and spinach, so they don't have to get very tall before they are harvested.

We lined the false bottom with the ever useful feed-bags. It is semi-permeable, and will allow excess moisture to drain away. We are hoping that the insulated air cavity below the plants will act as a thermal sink, heating up in the daytime, and holding some heat over through the nights.

We put a layer of fresh horse-manure down first, like a hot-bed, to provide a bit of heat and some extra fertility when the roots reach that depth.

Then dressed the top with a layer of well composted goat and sheep manure and potting soil.

This size freezer allows space for three rows of greens, 9 row feet in total. We planted two rows of zesty mesculn mix and one row of mizuna mustard greens. We have too many flea beetles in the garden come spring to plant these kinds of mustards, their favorites it seems. Even with row covers, the flea beetles come up out of the soil underneath, and really give our brassicas a hard time. But there's no flea beetles out now! I am even beginning to think that I could use the freezers as brassica sanctuaries in May. We usually transplant our brassicas to the garden in mid-May, but the tender transplants are quite vulnerable to flea beetle damage. If the flea beetles come out of the ground and have nothing much to eat, then they won't breed as rapidly. So I may try transplanting the young brassicas into the freezers mid-May, and let them grow a bit stronger, and past the prime flea beetle season, and put them into the ground as bigger plants in early to mid June. Too much transplanting can put a lot of stress on the plants, but if it is less stress than the pest damage, it may work out in our favor.

Finally a few sheets of glass on top to complete the cold-frames. Under a clear sky, it easily got to 35C (100F), and the temp can be regulated by sliding the glass sheets to leave vents. The day after planting, we got a snowstorm (another foot of snow!), and simply put the freezer lids over the top. It was holding at 3C (35F) with the lid on.


Mr. H said...

Hello Freija & Beringian,

I really enjoyed this post as I too am always trying to find another use for discarded items. Those cold frames will undoubtedly stand the test of time much better than my wooden ones.

I have often wanted to build an earth sheltered/underground greenhouse and thought you might be interested in this article from Mother Earth News I came across a few years back. I played around with the "cold sink" concept in my own little greenhouse last year without much success. Someday soon I would like to copy the design in the article below.



Country Girl said...

Very clever way to use the freezers. I will share this one with hubby!

ChristyACB said...

While I still can't imagine life without a freezer or frig, especially in summertime Virginia, I applaud your ability to and on top of it utilize the carcasses for good and wholesome work!

David said...

I think you mean mesclun not mescalin. Maybe not...

Chiot's Run said...

Very interesting. I can't wait to see how it works!

Freija and Beringian Fritillary said...

Mr. H, the one major advantage that I can see with the above ground insulated cold-frame is that it is free from the constant heat drain from the surrounding snow-covered ground that other in-ground or below-ground designs have. This way we only have to heat a small amount of soil, and keep it warm overnight. With our hoop houses, we could heat the soil all day long, but overnight, the surrounding soil would steal that heat very quickly.

So far so good, we thought of putting a couple of buckets of water in the space below the soil to act as a heat sink. It dropped to -5C (25F) overnight, after a day of snowfall, and the freezer, with the lid on all day, held at 3C (37F).

Country Girl, old freezers can often be found at local dumps, if you still have access to them out in the country. Or keep an eye out on big garbage day.

Christy, we refridgerate with water, hydro-cooling. Even the dairy products will keep in hydro-cool environment for over a week. Check out this great design for keeping produce fresh http://www.practicalaction.org/?id=zeerpots. Cooling can be achieved very well with moisture and a little breeze. But that may be hard to come by if you live in a very humid climate, unless you have access to a running stream or spring.

David, yes thank you for the correction, I went with the spellcheck, automatic!

Chiot's Run, we will post up our success/failures with this design. Looking forward to some greens!

Anonymous said...

Do you think one could be used to make a raised (deep) asparagus bed?

Freija and Beringian Fritillary said...

Anon, well I suppose they could. You would need to make some drainage spouts. It would certainly be worth a try, especially if you don't have the garden space. With constant contact with wet soil, the freezer would eventually rust out, but not for quite a few years, and probably only at the bottom, still providing insulation around the sides. If it works out for you, let us know!