I used 2 x 4s and 2 x 6s and lined the boxes with rigid sheets of styrofoam and heavy duty poly. I also reinforced the inside of the boxes with small, metal brackets for extra strength. All of this seems to have done the trick. We then ordered local soil for delivery and all I added for nutrients this year was a lot of bone meal and some organic fertilizer. We can add more next year but for year one this was a large enough investment.
Seeds were planted the first week of June and some starter plants from Arctic Farmer and Canadian Tire were added also. Progress for the first week of July (1 month of growing) has been slow but I blame some older seeds (Canadian Tire beans) and that the soil has limited nutrients in it. But bottom line.... things are growing and that is all that matters!
Photos show the new garden beds in Yellowknife vs. my Inuvik Greenhouse plot at the same time last year!
S.