Building a Hoop House Polytunnel and Cold Frames to Protect my Fall and Winter Garden

With the garden winding down and fall temperatures often dropping below the freezing mark its time to start protecting our winter greens.

In the spring we build these cold frames from 100% recycled materials ( ) and learnt about them through an interview with One Yard Revolution. ( )
The varieties we have chosen to plant this year are very hardy. Planting them in August should have given them enough of a head start to get established before the really cold temperatures set in. After our early frost the warm weather returned for awhile we have returned to night time temperatures well below freezing.

Placing the cold frame is fairly easy.  If you remember when we built them we put the glass on an angle so it could face towards the sun.  with the sun lower in the sky in the winter the additional angle allows us to place the lower side facing south in order to capture a little more of the direct sunlight. After figuring out which way is south we placed the cold frame on top of our winter greens.

Mounding soil around will help keep the cold frame insulated from the brisk air.  Soil traps a lot of air and acts much like snow as a fantastic insulator. 

After the cold frame was carefully insulated we placed black stones anywhere the sun could get to them.  These stones will heat up in the direct sun during the winter and slowly release it during the night helping to buffer the temperature changes at night.

Adding the cold frame according to Mr. Coleman of Four-Seasons Harvest has effectively moved the garden one and a half growing zones south.  Our little micro climate is now in zone 4 +.

Next comes the hoop house.  This is simple to install.  I chose to purchase coated rebar to help prevent rusting.  Drive the rebar into the soil along the edge of the beds on both sides.  Using the plastic electrical conduit a good friend of mine donated to me  fit it over the rebar on both sides.  You will want enough supports to prevent sagging or run a support at the peak of each rib connecting them all together.

Once complete its simply a matter of taking 4mm greenhouse plastic or greater and draping it over the frame.  Using scrap lumber and more black stones carefully secure it so that no cool air can sneak in.  This second layer of protection has moved us one and a half zones south to Zone 6.

Its important to remember on sunny days even below freezing the cold frame and hoop house can heat up quickly.  Make sure to open one end of the hoop house in the morning and crack the cold frame.  Close it up at night and your veggies will be nice and happy.

I look forward to hopefully pulling fresh greens from the garden late into the fall and hopefully early winter!

About Stephen

The Alberta Urban Garden Channel hopes to promote organic gardening that is simple, sustainable and does not have to cost a lot. We do this by investigating the Science behind gardening, methods, practices and products to make sure that you will have the best chance of successfully growing your own food at home.


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