Building Low Tunnels to Extend Your Garden Season  

As fall approaches, many gardeners put their garden to rest until spring. Instead of giving up fresh veggies, why not build a low tunnel? A low tunnel is an easy to build, inexpensive structure that can protect cold tolerant crops, even when there is snow on the ground. Most vegetables or herbs that you would typically grow in a fall garden – hardy greens like kale, chard, and collards, turnips, carrots, beets, arugula, leeks, parsley – would be ideal for a low tunnel.

So what exactly is a low tunnel? It is a mini greenhouse that can be built over any garden bed. A low tunnel creates a microclimate that allows many vegetables to survive the winter. And although most plants won’t actively grow in winter due to fewer hours of sunlight, a low tunnel lets you continue to harvest crops, and gives plants a jump start once spring arrives and daylight increases.

Supplies:
● 10-foot lengths of ½” PVC pipe (1 for every 3-4 feet of garden bed)
● 3.5 mil plastic sheeting
● Section of iron rebar, to make holes in the ground
● Sandbags, large rocks, or bricks (Something heavy to hold the plastic down)
Optional:
● ¾” Pipe straps (to attach low tunnel to a wooden raised bed)
● Large binder clips (to secure plastic)

Building the Low Tunnel:
To build a low tunnel directly over a garden bed, use a section of rebar to make 10” holes along each side of the garden bed, every 3-4 feet (use the shorter distance if you get a lot of snow). Stick one end of a PVC pipe into a hole, bend into an upside “U” shape, and slip the other end into the hole on the opposite side of the garden bed. To attach the low tunnel to a raised bed, screw pipe straps onto the sides of the raised bed and slip the pipe into the straps. Depending on the width of the bed, you may need to cut down the pipe, since you will not be burying any of the length. Roll the plastic out over the frame you have made. For extra security use binder clips to attach the plastic to the pipe frame. Trim the plastic so there are a couple of feet extra all around, and secure with sandbags, large rocks, or other heavy objects.

Special Considerations:
If the weather gets above 60°, the heat can become too intense in the low tunnel for plants to survive. Keep an eye on the temperature, and vent the tunnel if needed by opening up the ends or flipping up the sides. Conversely, if the forecast calls for extended below freezing temps, it’s a good idea to have some floating row cover on hand to throw over the top for added protection. Every garden should have a low tunnel or two, to enjoy fresh veggies even in the dead of winter.

About the Author:

Mia Cover is an avid home gardener and beekeeper, and she runs a garden club at an inner-city high school. She lives with her husband and kids on a tiny urban farm in Nashville, TN.