The Basics of High Tunnels for Crop Production


Deb J. HolleyIf you haven’t worked with a high tunnel (also called a “hoop” tunnel), fall is a great time to become acquainted with how these micro-environments allow you to grow fresh and delicious fall, winter, and early spring produce, even in geographical areas not usually warm enough to accommodate such produce. I’ve always enjoyed growing produce in these off seasons — cooler temperatures in which to work, no weeds, and, with no pests to ravage your crops, no pesticides or residues on your food!

Young Lettuce Plants in Tunnel

As a rule of thumb, high tunnels are thought to boost your local growing capability one zone warmer on the USDA Plant Hardiness Zone Map. For example, if you’re normally in Zone 5, the use of a high tunnel can increase your growing ability to Zone 6. Many gardeners use high tunnels for “season extension”, meaning that the tunnel can give crops a month or more of viable growing temperatures compared to being planted outside. However, if row cover is used in the tunnel in colder regions, lettuces and greens can normally survive the entire winter. They can even endure an occasional nighttime temperature of 20 degrees below zero while continuing to produce into the spring.

Exterior of Small High Tunnel

What exactly is a “high” tunnel? These structures usually are constructed of steel or PVC plastic pipe frames, covered with UV-resistant clear film, and are tall enough to enter. They have one or more doors so that the tunnel can be accessed all year, even in winter. Note that there are also low tunnels of various types, which are only three or four feet high. The term “hoop tunnel” actually can refer to either of these types of structures.

Interior of Small High Tunnel

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