This year was our first attempt at season extension. Since we are all about recycling and reclaiming materials, we incorporated that into our strategy. Last summer we scored a bunch of used tractor tires from a local farmer. They have to pay to dispose of the tires, so he was super happy to let us haul off as many as we could fit on our trailer. At the time, I didn't have a solid plan for what I would do with them but it has evolved over the winter.
Growing up, people built elaborate tire structures to grow tomatoes in. They claim that the tires kept the soil nice and warm, therefore growing better tomatoes and other warm season plants. Tomatoes prefer soil temperatures around 85 degrees F (http://homeguides.sfgate.com/effect-soil-temperature-tomato-growth-45509.html). Since I live in the great white North - this can be hard to accomplish outside. The tire idea appealed to me.
Around February, when winter had been dragging on way too long I had another idea. I started lettuce, spinach, and kale inside on my seedling mat with a grow light. At the end of March, I transplanted them out into one of the tires and used a ripped up row cover and two of my hoops to make a modified hoop house over the tire. The resulting structure looked a little like a landing pod from Apollo 12, but it worked. And it made me really really happy to be gardening in March!
We had a little bit of a slow start, lost a few spinach plants to a rodent, and struggled with a really cold wet spring. Overall though, our little experiment was a success and I have been eating lovely greens from my garden all week. Considering that we would like to eventually operate a Community Supported Agriculture program, we need to be able to provide produce starting mid-May. Between various greens and asparagus, I think this is possible. But only with season extension!