How to Build a Low Tunnel Bed Topper

Hey there! Today we’re talking about how to extend the growing season by using low tunnels and mini hoop houses 🙂 Also referred to as grow tunnels (and similar to cold frames), low tunnels use a semi-circle frame and either frost cloth or some sort of plastic sheeting to protect crops you’re growing.

They work by trapping heat from the sun that warms the soil a bit and also protects crops from things like frost and snow. It’s all based on the greenhouse effect, which raises the temperature around the plants and helps them continue growing. So let’s talk about how I put together a hoop house topper for my raised beds!

Supplies used

• Garden hoops
• Frost cloth
• 6-mil clear plastic sheeting
• Measuring tape & scissors

Step 1: Assemble hoops

First you’ll need to assemble each of your hoops. The set I got with came with 36 fiberglass “sticks” and a bunch of connectors. I connected a few of the sticks to see how long I wanted them to be. I ended up using 6 sticks per hoop based on the width of my raised beds and the height I wanted the hoops to be.

After assembling 6 of these and using all of the pieces that came with the kit, I put three in each of my rectangular beds. One on each end and one in the middle for support. To put them in place, I just stuck them down into the raised bed soil and gently packed the soil in around them for stability.

Step 2: Add frost cloth

If you are only need to extend your growing season a bit in the fall—or if you’re starting a bit earlier than normal in the spring—you’ll likely just want to use frost cloth. I ordered this frost cloth kit that also came with additional clips.

This cloth is lightweight, breathable, and lets some water through. It also lets 85% of sunlight through, which is a good amount for growing plants. See below for how see-through it is with my hand behind it—as well as a look at the clips that came with it (the metal ones). The green clips came with the hoops.

You’ll want to cut this to size based on your bed’s measurements. I decided that I wanted my frost cloth to cover the beds but not go all the way down to the ground. So I used regular scissors to cut the cloth down and and attached it to the hoops using the green clips that came with them.

After those clips were in place, I used the metal clips that came with the frost cloth to attach everything in place to the perimeter of the raised bed. And that’s it! Monitor for the need to water more depending on what you’re growing, the weather conditions, and how much water is getting through the cloth.

Step 3: Add plastic sheeting

If you’re need a bit more protection and more of a “greenhouse effect” for your plants, you can also add plastic sheeting. I bought a large roll of 6-mil clear plastic sheeting from Lowe’s and used that. It looks pretty opaque, but that’s just because it’s thick. It does let some light through.

And it also heats up much more then just the frost cloth does because it is less breathable! This can be helpful if you’re trying to germinate seeds that might need a bit more warmth to germinate but grow fine in lower temperatures.

For the plastic sheeting, I cut it down to size so that I could use random rocks and brick pieces to weigh it down on the ground. I wanted the “greenhouse effect” to extend to the raised bed area to hopefully warm the soil up a bit more.

I’ll plan to open up the ends of this setup for some increased airflow once it warms up a bit in the very early spring. And of course water cannot penetrate the plastic sheeting, so you’ll need to check to make sure the soil doesn’t need more moisture every so often.

And that’s it! I’ll be very curious to see how early I am able to start growing in these beds. And considering I am trying to germinate cold-weather crops as of December 15th, I’d say I will get a pretty good sample this winter of what’s possible!

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