A frost cover for a raised garden bed

I’m never ready for gardening season to end, and here in the upper Midwest that end can come quickly — the average first frost in my area happens in mid-October. So I’m using a frost cover with my raised garden bed to try to extend the season a bit longer. (To see how I assembled the raised bed, see this post.)

My goal here is modest — I’m just trying to keep some salad greens and radishes growing into the late fall. These are cool weather vegetables anyway, so they’re content with lower temperatures as long as they don’t freeze. By contrast, tomatoes and peppers, which are already pining for Italy, probably aren’t going to last even if the temperature stays above 32 degrees Fahrenheit.

The thing about fall frosts is that they come and go unpredictably. An early freeze might be followed by weeks of moderate temperatures. So if you can just keep the plants going through those first few nights of cold, you can potentially get a lot of extra growing time.

Frost covers don’t have to be fancy. Light towels, burlap, or even cut-off milk jugs for individual plants can work. In the past I’ve thrown an old bedsheet over vegetables to protect them.

This year I wanted something a little better. I considered this DIY solution from The Garden Glove blog that uses Pex pipes, a clever repurposing of plumbing supplies. In the end I decided on this Growneer Garden Hoops kit and this frost cover.

The setup is pretty simple. You put together the number of fiberglass rods that you need with metal connectors (if you’ve used modern tent poles you have the idea). These rods form hoops that create a frame over your garden. Nothing is really attached; the tension of the bent rods against the sides of the raised bed keeps them from separating.

The instructions suggested using five rods, but four worked best for my two-foot-wide bed. I simply pushed them about a foot into the soil at the edges. I feared that the rods would fail because they would be curving more than what was recommended, but they seem to be holding up. 

With the frame in place, I next cut the frost cloth to size with a scissors. I left plenty of overlap and I didn’t cut it very prettily, but this is more of a functional project than an aesthetic one.

The kit came with plastic clips to affix the cloth to the rods. These were a little tight but they worked. I also clipped the cloth to the raised bed itself. I ran out of clips at the end so I used a few clothespins. You could probably use binder clips or whatever you have around.

In the past I’ve found that the wind can easily get under the fabric and blow it off the plants in the night. That’s what happened last year with my bedsheet, and my exposed lettuce froze. So don’t overdo it but make sure you have that frost cover secured.

Most people recommend removing the cover during the day so the plants can get more light and air. That said, I doubt that it will make much difference to leave it on if you’re expecting frost for a few nights in a row.

My plants have already come through one frost safely with the cover. It looks like they’ll get to Halloween and — who knows? — maybe even Thanksgiving.

Feel free to share your late-season gardening tips in the comments!