Some folks use poly-tunnels to extend the growing season. I wouldn’t pretend to be the expert that Eliot Coleman is on poly-tunnels but I’m not a huge believer in them. I don’t like getting hung up on high-tech technology such as poly-tunnels. They’re expensive and difficult to maintain and will become increasingly so because of their oil component. I prefer to look at cultures that deal with cold climates and see what they were growing before World War II, before the widespread use of hybrids. If they were agrarian, most of these cultures survived on root vegetables. So we grow root vegetables and root cellar them. An older season extender is a cold frame. To me, these make sense, especially if you tuck it up against the warmth of your house foundation on the sunny side of the house. It might be possible to have cold weather greens through out the winter if you keep the snow off it.
Better yet, is the longkeeper tomato. Nothing beats one of your own tomatoes eaten fresh off the kitchen counter in January or April. Last year, we grew a couple of varieties – Mystery Keeper from Mapple Farm and Ruby Treasure from Prairie Garden Seeds. We didn’t have much success with Ruby Treasure due to late blight but we were able to salvage a half-dozen Mystery Keepers.

Dec 20, 2010 Jan 14, 2011
Feb 21, 2011 Mar 27, 2011
All of the cut tomatoes ended up in bacon, lettuce, and tomato sandwiches. They were juicy and a bit acidic but that didn’t matter in the sandwich. They weren’t spectacularly flavourful but who’s a tomato connoisseur in the depths of winter. We have two tomatoes left and we’re going to see how long they last.

This is great info! I have some “keeper” tomato seeds I am trying for the first time this year! I can’t wait to see how long they last.
May 30, 2011 – They are beginning to dry out but the flavour is still there. They’re fine on a hamburger but not by themselves.