Ideas For Keeping USFG Raised Bed Warm In Winter

I'm growing my first winter garden after building a Ultimate Square Foot Garden Raised Bed. To hold the greenhouse fabric in place I tried some stainless steel tablecloth clips that are meant to be used on picnic tables but they're not working out.

The slide off and leave the plastic flapping around allowing cold air to come in.

There was a quick solution to that problem which creates a much better air seal and I have an idea for an easy way to provide some additional heat which won't cost a lot of money.

Securing The Greenhouse Plastic

One of the main reasons for creating a lip around the USFG box (besides looking cool) was to have a place to attach things. They can even hold spring clamps.

The plan is to lay a piece of wood lath over the edge (or maybe under it) so the greenhouse film is sandwiched between the lip and the lath. Spring clamps will hold it all together as shown.

This needs to be done on all 4 sides. It works out well but I haven't taken a photo because I haven't gotten the right clamps. Plus it's cold out. Next time I'm at Home Depot I'll pick up a few of these HDX 2" Spring Clamps plus a bundle of lath so I can take a decent photo. Other manufacturer's would call these 6" clamps. 2" is the clamping capacity. I think it makes a lot more sense to name them that way.

I have this set up right now but without enough clamps. It holds the greenhouse plastic down more securely and keeps air (and squirrels) from getting in.

Electric Frost Protection For Covered Raised Beds

I'm just using a heavy green house film but I might also try a wooden cold frame cover in the future. Either way this next bit will help keep the temperature up on cold nights to prevent frost. Best of all it shouldn't cost much.

I was searching for something else on Amazon when I found this Farm Innovators TC-3 Cold Weather Thermostatically Controlled Outlet. It plugs into an outlet (but in this case an extension cord) and has 2 outlets that are controlled by a thermostat. When the temperature is below 35 degrees the outlet turns on, providing power to whatever is plugged into it. When the temperature reaches 45 degrees it turns off.

This is the perfect temperature range to prevent frost without having to provide a lot of heat. It's important that the raised bed is sealed fairly well to prevent heat loss through air escaping.

I haven't tried this yet, probably won't until next year but the idea would be to have an extension cord run to the first box and the end attached inside the cover. Near one of the PVC tubes, mounted on the bottom near the soil since that's where we care about the temperature not going below freezing the most. A simple outdoor lamp holder is plugged into the TC-3 outlet and run up to the top of the cover where it hangs down. Heat will be provided by a single 100W (maybe even less) incandescent light bulb.

Ideally another extension cord will run from the first extension cord to the next box, and not from the TC-3. To do this an outlet adapter that converts 1 outlet to 3 will be necessary since most outdoor extension cords only have one outlet. Each box will have its own TC-3 for better control.

Since there are 2 outlets on the TC-3 you could daisy chain them (plug the extension cord into the TC-3 and run it into the next box) and save some money but run the risk of having improper heating. If for example the first box is sealed better than the second, the first box may be at the right temperature but the second may be below the freezing point and the lights won't come on.
Was this article helpful? If so please help by sharing it.


  1. winter garden! what a lovely idea. :-)

  2. Thank you. I'm still not sure how it's going to turn out. The radishes were almost ready but I was due to water it and now it's covered in snow!