Extending the season
First question: What are we extending? In our location here in CNY, I'll be keeping track of our first and last frost dates. These dates for CNY can vary, of course, depending on elevation or other geographic features. Our first frost date in 2012 was October 12, which is in the normal range. (We generally think of May 10 as the last frost date, but we'll see what happens in 2013.)
Here's John building a coldframe using pieces of our old cedar fence and some other scrap wood. We had kept the slats from our cedar fence when we took it down, and they've found many uses. The glass cover for this coldframe was a window we collected from trash put out to the curb. We designed our various coldframes around the size of the windows we had collected.
We added styrofoam insulation, covered in black plastic, to this coldframe.
The black plastic sitting on the soil inside the coldframe is there temporarily just to warm up the soil before we plant our spring crop.
Here in Central New York, there can be a lot of snow and ice. In early 2011 we had four feet of snow on top of the cold frames. It's amazing how plants survive, even within the protected space of the coldframe. But they do!
Actually the snow cover is a protective blanket. In 2012, with almost no snow, the plants in the coldframes did very poorly. Perhaps on those sunny days the air inside heated up too much and scorched the plants.
This lettuce was started indoors in September and transplanted out in early October.
In December growth comes to a halt, but, when the snow melts, the soil warms and the amount of sunshine increases. The plants start growing again.
Coldframes are useful not just to extend the season into the fall, but also to get started earlier in the spring.
And you can cover the cold frames with row cover material to reduce insect damage.