Many gardening books and blogs and seed starting tutorials will tell you that If you’re going to grow things from seed, you really must have grow lights if you want to avoid ending up with sad little spindly seedlings. In the past I’ve been pretty successful with seedlings grown on my south-facing windowsills without the help of grow lights, so it certainly can be done.
This year there are so many things I want to start from seed that I probably don’t have enough windowsill space for everything. Still, I didn’t really want to spend a whole bunch of money on grow lights, and I don’t know where I’d put them in my little house anyway, so I decided to go with a low-tech solution. Scott found an old window at the dump and some old boards in his attic, and put together a nice little cold frame. It cost zero dollars and took maybe an hour.
I moved my little onion seedlings out there on Friday, along with some mesclun, kale, chard and other greens that I started a few days ago. It’s about 36 degrees here today, but inside the cold frame it’s a balmy 60 degrees. It does get cold in there at night, but the cold frame does offer a few degrees of frost protection, and the onions and greens are cold tolerant crops, so they can handle it. Hopefully we’ll be eating salads of homegrown baby greens in just a few weeks! Next fall I’ll use the cold frame again to grow greens through the winter.
Another advantage of the cold frame is that the seedlings are being exposed to the elements from day one, so they won’t need to be hardened off before they’re planted in the garden. They’ll be stronger than seedlings that spent their first weeks being coddled indoors.
Hudson Valley Seed Library has a tutorial for building a cold frame, and another for starting seeds in one. They suggest using a clear corrugated plastic material for the lid, but you can also use an old window or even clear plastic sheeting stapled to a wooden frame. You just need some sort of frame, and some sort of transparent lid that you can open and close, and prop open on warmer days so that your seedlings don’t cook.
Here’s another one made from a window. You’ll notice most cold frames slope downward in front. This gives you maximum sun exposure. We didn’t really think about this, so mine is flat just because it was easier. Less cutting and less math. I was looking at mine this morning and noticed that the front of the frame casts a nice long shadow over the inside of the box. This will be less of a problem in a few weeks when the sun is higher in the sky, but still it’s probably best to suck it up and do it the right way.