Installing a Low Tunnel
For gardeners in our region, using low tunnels on raised beds can extend the growing season and get you close to year round gardening. With this low tunnel design, the garden beds will be 3-4°F warmer than the outside temperature. Low tunnels can be added to beds growing fall crops planted in August and September.
Constructing Your Low Tunnel
Here are the steps to take to build your low tunnel. At the end of this post, you’ll also find a video demonstrating low tunnel installation.
Step 1: Gather Your Materials
The following list of necessary materials (this list is enough for one 4’x8’x1′ garden bed). Click on the links for vendors:
5 PVC poles
16 pipe straps
36 wood screws & matching drill bit (included in package)
12 feet of Agribon 19 row cover
10 bricks
Yardstick or tape measure
Permanent marker
High powered drill
Step 2: Mark the Raised Bed
From the end of the garden bed make a mark with the permanent marker at 4″ a second mark 29″ from the 4″ mark, a third mark 29″ from the second mark, and a fourth mark 29″ from the third mark. The final mark should be 4″ in from the opposite end of the bed. If you have a tape measure you can make the marks at the following intervals: 4”, 33”, 62” and 91”. Do this on both sides of the raised bed. Measuring and marking is one of the jobs students can work together to complete.
Step 3: Mark the PVC Poles
Using the permanent marker, mark 8” in from one end of the PVC pole. Holding the other end of the PVC pole mark 40” from the bottom (this mark will line up with the top of the garden bed) and 32” (this mark will indicate where you need to cut the pole).
Step 4: Attach the PVC Poles to the Bed
Align the 8″ mark on the PVC pole with the top of the garden bed at one of the marks made in step two. 8″ of PVC will allow you to install two pipe straps that will secure the pole to the inside or outside of the bed (for cedar beds it is best to put the pipe straps on the inside).Use the pipe straps and wood screws to attach the PVC pole to the bed at the 8” mark and then again about 1” from the bottom of the PVC pole. This is a task for two students and one adult. One student should hold the PVC pole in place, a second student should hold the pipe strap while the adult uses the drill to secure the pipe strap with the screws.
Once you have one side of the PVC pole attached, bend the pole so it is directly across the bed, creating a half circle and line it up with the mark made in step 2. Measure the height of the circle created, this should be about 28”. An adult should use the PVC cutter to cut the PVC pole at the 32” mark made in step 3. Secure the PVC pole to the opposite side of the bed using the same method described previously until all four PVC pole are attached, creating hoops along the length of the bed.
Step 5: Add the Stabilizing PVC Pole (optional)
Place your final PVC pole along the length of the bed. Mark the pole at each point where it touches the PVC hoops that are secured on the bed. At each mark drill a screw through the first layer of PVC-don’t go all the way through the pipe. After all four screws are secured cut the PVC at each end so there is as little as possible sticking out. This will reduce the possibility of having the row cover (attached in next step) get snagged and tear. Have students hold the trimmed PVC pole with the screws facing up so an adult can complete the drilling of the screws into the center of the hoops from the underside.
Step 6: Anchor the Row Cover
The row cover we suggest in step one above reaches the ground on both sides of the width of the bed when centered. It’s very important to be able to anchor the row cover on all sides of the bed, so before cutting make sure to test you have the right length! Anchor with bricks so it is secured on all sides.
Using Your Low Tunnel
Once installed, it’s easy to put up the low tunnel each fall and take it down when the weather warms back up. On warm days in the fall, it’s best to pull back the row cover so the plants don’t get over heated and potentially burned. This simple design allows you to enjoy your fall crops longer and even helps hardy crops overwinter.
Check out our video on Fall Season Extension to learn more and see a low tunnel being installed: