When I built my cold frame last fall out of an old window and $15 of materials, I had visions of harvesting Swiss chard, arugula and lettuce all through the winter. After the sub-zero temperatures, snow, thaws and grey days of the past winter, I realized my expectation was pretty unrealistic. But that doesn’t mean my cold frame was built in vain: I think I’ve figured out what it can do well.

I didn’t end up getting a single salad out of the cold frame, but it did keep a surprising number of greens alive all winter long. I had two rows of arugula there, which survived without a hitch! They didn’t grow much at all, but I think the plants will take off like wildfire in April, giving us a jumpstart on a harvest. A few spindly carrot seeds sprouted, but haven’t grown much at all. I transplanted a few lettuce seedlings (the variety is mervielle de quatre saisons – translated as “marvel of four seasons”) and they’re looking strong but small – I expect a similar boost in growth during April. We had a small potted rosemary plant that I dug into the cold frame, pot and all – and it survived splendidly, giving us fresh rosemary all winter long (I went easy on it, picking just s few sprigs here and there.) The Swiss chard survived equally well, but some less hard greens, like curly endive, froze and rotted.

The best winter use for a cold frame is to protect perennials that need warmer winters than I can give them. Next winter, I’ll transplant all my non-hardy perennial herbs – thyme, rosemary and oregano into the cold frame. If I can clear the space early enough, I might also sow some parsley seed in it as well – my parsley survived pretty well without the cold frame, and already has some lush green undergrowth.

The other way I’ll use the cold frame is to acclimate my seedlings to the outdoors in the spring. I’ve never bothered with this step in the past, but the seedlings I start myself always seem to lag the nursery-bought ones. So it may help.