Try row covers on cool-weather plants

Frankly, they look a little like Halloween decorations: billowy, semi-sheer white fabric pieces draped over two of my urban garden’s raised beds. Ghostly.

What I’m hoping they’ll do is anything but scary. These floating row covers can protect plants from wind and dropping temperatures as we stream through fall and into winter, and I’m counting on them to extend my growing season.

Row covers aren’t the only way to do this – greenhouses and outdoor beds with covered hoops are two of the others – but the fabric is surely the simplest and cheapest, the equivalent of a lightweight scarf over your head. I spent just a few dollars on many yards of a medium-weight fabric that lets in 85 percent of the sunlight plants need to grow, while giving those plants up to 4 degrees of frost protection. Four degrees might not sound like much, but it could translate into many weeks when the plants are warm enough to keep growing, or at least to survive.

For even more frost protection, I could be using a heavier fabric, but the trade-off is that it lets in less light, so the plants won’t grow as quickly. It’s not time for that yet.

I put my covers down last month, one of them on a bed where I had planted seeds for carrots, radishes, beets, kale and spinach a few weeks earlier, and another on a bed where I had just sown some spinach and arugula seeds.

Come spring, if we don’t have another harsh, killing winter, the fabric should be able do even more magic.

“With spinach, arugula, certain lettuce varieties and even kale, if the plants go into the fall, and they’re immature but healthy, and there’s a row cover over them, in March, when the regrowth starts, they start growing like crazy,” says Jon Traunfeld, extension specialist and master gardener program coordinator at the University of Maryland. “The growth can be incredible. They’ll be way ahead.”

Some caveats: Even though row covers increase the temperature of the air surrounding the plants and help them maintain more moisture even as the winter air gets drier, they won’t make a difference in one of the most important factors of vegetable gardening: soil temperature. So gardeners who think they can get a late start on sowing seeds in the fall if they use a row cover will be disappointed. And if you use them over plants that require pollination, such as squash, you’ll need to uncover them and let the pollinators in at some point if you hope to have any fruit.

The fabric – usually spun-bonded polyester, UV-treated to withstand the sun – also can help protect against pests, which is the main reason some gardeners use them. I haven’t had much of a pest problem yet, but that could change as quickly as, well, the weather.

Some gardeners bury the edges of the fabric in soil to keep them in place, but I used bricks. It’s best to avoid staking the fabric, because one tear could be exacerbated as soon as the wind starts whipping things around.

I also used a generous amount of fabric and left a lot of slack so the plants would have room as they grow.