The Slacker Gardener's Coldframe

I'm late! I'm late! For a very important date! The late season planting date, that is.

Although I worked a larger garden this year than I ever had before, I still feel like a slacker. An extended growing season really isn't part of my garden repertoire so far, though the advantages are obvious to me. I have no greenhouse, no row covers, and I didn't manage to get a second crop of anything in for fall harvest, not even lettuce. And it's pretty late to do anything about it now, in November. But if I'm not the most diligent gardener, I am willing to gamble on long shots. But in this case, I'm hedging my bets.

I've come up with a crude coldframe idea, and I'm going to run a little experiment. What I'm trying to grow is arugula sylvetta, (also known as rocket) a very hardy and very tasty salad green. It's tough enough to germinate at temperatures as low as 40F (4.5C)! And it may be my favorite salad green of all time. We especially love it tossed on thin crust pizza just as it's pulled from the oven. I'm going to see if it can be coaxed into producing a winter crop for us when planted this late in the season. Here's the set up for my experiment.


We picked up some older bales of hay from the farmer who leases and farms our farmland. He declined to charge us anything for them. (He'll be getting a few loaves of my homemade bread next time we're up there.) If he'd had any, we would have taken bales of straw, to avoid bringing seeds into the garden. I arranged four of the bales to form the sides of a small impromptu coldframe, which I'll use only over this winter. I call it the hayframe. In spring, the hay will be turned into garden mulch. Hay is a good insulator that breathes well, and it's biodegradable. Best of all, constructing the walls of my coldframe took less than five minutes and cost me nothing. If you had to pay for four bales of hay, it would almost certainly cost no more than $20, and less if you live outside of a city. Straw bales may be even cheaper.


The top of my hayframe is a weather beaten window I picked up from a typically frugal old time Pennsylvania Dutch man. Throw it away? No, ma'am. He set it out in the yard with a for sale sign. I got it for $2. I pinwheeled the bales of hay to create an opening just slightly smaller than the outer dimensions of the window. The slight overlap of the bales at each corner provides extra insulation, at least in theory. In reality, hay bales aren't as uniform or as solid as bricks, so there are gaps and irregularities. The window simply lays on top of the bales, so the seal isn't great to say the least. But I guess I've got what I paid for. I did stack the hay bales so that their shortest sides are the vertical rise of the coldframe. That means that whatever warmth is collected inside the hayframe will stay as close to the ground, and the plants, as possible. I'm counting on the cold tolerant arugula to make this setup work for it.

In hardiness zone 6, I know I'm asking a lot from these seeds, planting them in early November, though we are having unusually warm weather this week, which may make all the difference. To give the plants a little more advantage in this marginal environment, I pulled a few tricks out of my bag. First, I aligned the coldframe to face south, so that it ekes out as much solar exposure as possible. I also cut pieces of cardboard to fit each hay "wall" of the hayframe, and I covered these with aluminum foil, shiny side showing. This will bounce whatever sunlight comes into the coldframe around very well, so that the growing plants get as much sunlight as possible.

I haven't done this yet because it has been fairly warm, but I may also put two bricks in the cold frame, one at either northern corner. These bricks will soak up the solar energy each day and get somewhat warm. During the night, they'll slowly release that warmth, giving the plants a small temperature advantage. Placing them in the corners will assure that they won't block too much of the sunlight reflected from the aluminum foil, and they won't shade the plants directly either. I'm going to wait to see what the daytime temperatures are like in the hayframe on a cold sunny day, the next time we have one, which may take another month.

I'm pleased with this little project because it puts stuff we've got lying around or very cheaply available to us to good use, at least potentially. I'll be even better pleased if it works. Plenty of things may go wrong with this experiment. Field mice could invade the hay bales. They might enjoy arugula. The window frame is also going to collect precipitation, leading to rapid deterioration of the wood. But that's just something I'll have to live with. Or, I may just have left the sowing too late. So, we'll see how the arugula seeds fare. I'll let you know how it goes.

Note: Preliminary results of the hayframe experiment are now posted.