Tuesday, November 24, 2009

A Quick, Inexpensive Polytunnel

With my leeks not maturing as fast as I wanted them to I decided to give them some protection so they overwinter. I also needed a bit more covered space for potted perennials that I neglected to plant. I wanted something inexpensive, fast to make and strong enough to withstand a foot of snow at a time. This tunnel is a hybrid version of quick hoops and my own ideas. I put the whole thing together last Sunday afternoon in about an hour. Should I leave out the part when I had to go back to the home center because the bolts I bought were to short, maybe I will keep that part to myself....

Above is all the materials you will need to make the frame, Total cost for these materials was about $17 cdn not including plastic. Materials include:
  • (4) 1/2"x10' pvc electrical conduit
  • (3) 1"x2"x8' lumber
  • (4) 2 1/2" bolts and nuts
  • (4) washers
The only other thing you will need is enough plastic or row cover the fit the tunnel. I used plastic I had on hand, I would prefer row cover but I didn't want to wait for an order to arrive.

To build the tunnel start by placing one end of the conduit in the ground 12-18" deep and then bend the other end down placing it 12-18" deep as well. My bed is narrow so I ended up with a tall tunnel but it will also fit a bed 36"-48" wide. Continue placing the conduit, evenly spaced up to 8' long. With all the conduit in, cut one 1x2 to the length of the tunnel and fasten it in place.

Fasten the 1x2 in place by drilling a hole through the conduit into the 1x2. Then place your bolt through the hole and tighten everything in place with the washer & nut.

The top 1x2 will lock all the conduit into each other and will stop snow/rain from pooling on top. Now the only weakness is the tunnel will sway from wind and snow pressure. I solved this problem by cutting the other two 1x2's into stakes that were 12" higher then the tunnel.

These two stakes were then driven into the ground on either end to correspond with the top 1x2 brace. Once firmly in the ground I pre-drilled into the top 1x2 and added two screws to fasten everything together. Now you will have a frame that will survive high winds and heavy accumulations of snow.

With the frame all done I placed the plastic on the frame leaving about 6" extra on each side. I weighted down the plastic with heavy rocks and also buried the back edge with soil to further weight it down. The front edge I want to have easy access to so currently I have just tucked the plastic down. Before the weather turns bad I will be picking up either Greenhouse clips or binder clips to hold the front plastic in place.

Now for what will be in the tunnel:

Chard. The empty spot behind will be for overwintering potted perennials. Come
spring the perennials will come out and I can use the space to harden off seedlings.

A lone tatsoi, get growing tatsoi!

And the main reason for the tunnel, my late planted leeks. As long as
they overwinter they should be ready for harvest some time next spring.

After I was done the tunnel I put the barrel greenhouse back in place that I made last winter. I will be transplanting some greens into the barrel soon and place plastic on it after that. I think I may plant some tatsoi in the barrel as well. If we have a warm December they may just grow.


  1. That should work really good, Dan. I really like the electrical pvc conduit, because it will last much longer than schedule 40 pvc. Have you thought about using snapclamps for the ends?

  2. Very nice! Good luck with the overwintering!

  3. Very nice! Simple, functional & cost effective!
    Good luck to you, and the Tatsoi ;-)

  4. You make me feel really lazy. I'm not going to try to overwinter anything except my spinach and I'm just going to drape remay over it without any supports. Right now it has some supports, but it won't once winter hits. The snow would just knock them down.

  5. Top work there Dan! Although in my part of the world there really is no need to overwinter hehehe. Although a foot of snow sounds like a lovely idea!

  6. I like that. I'm looking for good and simple ideas for fall and winter gardening. This one's a keeper.

  7. EG - I just looked up the snapclamps and they look exactly like the greenhouse clips. I wonder if I can source the snapclamps cheaper.

    Cloud - Thanks, I hope they live.

    Fred - Thanks. I got your e-mail the other day, I must get to replying tonight!

    Daphne - I had to do something to get these leeks through winter. I hope it works.

    Prue - Yes, no need for cold protection in Australian. Maybe sun protection though.

    Sande - They are really easy to put together. You could have greens in no time once the light starts strengthening during march.

  8. This is great! it is amazing what and how much you can grow under a covered area through the winter. We use a recycled old awning against the house for overwintering plants in pots etc.
    Keep us posted on the wee tatsoi!

  9. Ahh that's just what I need on my patch! Just the right shape for the snow to just slide off so as not to put too much weight on them.

  10. The narrowness of the bed is going to really work to your advantage. It creates a more pointed peak as then strengthened by your top bar connector - all of which should encourage snow to slide off rather than accumulate and weigh down the hoops and plastic.

    Good work!

  11. Looks great and to see green in Canada is very nice!

  12. looks easy enough for me lol! Thanks :) Happy Thanksgiving :)

  13. We need a green house.....great job on the tunnels....