With winter right around the corner I have been working on finishing the mini-greenhouses. The night temps have been fairly stable with a few nights in the upper 30's, but we still haven't had our first frost yet.
I have finished building the 2nd mini-greenhouse this past weekend. I have purchased some coiled row cover wire from Johnny's to support the row covers inside. The wire comes in a 60' roll that you can cut to the lengths you choose. I cut mine in 63" lengths for the lettuce and a little larger for the cabbage, broccoli and cauliflower.
The row covers should offer enough protection for now, but in another week or so I am also going to cover each unit with 6 mil greenhouse plastic. Eliot Coleman, in his book The Winter harvest Handbook, calls this method of double layered protection "twice-tempered". Eliot states that "the inner climate is moved three USDA zones to the south" and winter vegetables with thrive under these conditions. Everything seems to be coming in nice, so hopefully we will be harvesting lettuce and other winter veggies throughout the winter!