Winter Growing & Season Extension
Winter Low Tunnel Protection Methods

Overwintering in Low Tunnels

Winter Growing Guide

  1. Introduction to Winter Growing
  2. Winter Production in the High Tunnel
  3. Winter Harvest Planting Dates Chart
  4. Overwintering in Low Tunnels
  5. Overwintering Planting Dates Chart
  6. Crops and Varieties for Winter Growing

Low tunnels are constructed from hoops (we created ours with Quick Hoops™ benders) that are positioned over crops to be overwintered. The hoops are first covered with row cover. With the approach of deep winter they are then covered with a layer of plastic film.

Hoops

woman bending support structures for tunnels

Benders can be used to create DIY high tunnels or low tunnels.
onions for overwintering planted in a low tunnel

Low tunnel on the Johnny's Research Farm, planted with overwintering onions.

We developed the Quick Hoops™ Low Tunnel Benders specifically for creating hoops from bent steel conduit (aka electric metallic tube, or EMT). We have found that hoops made of EMT are strong enough to support heavy winter snow loads, whereas other materials, such as wire or PVC, fall short in this regard.

Using different bender styles, 3'-, 4'-, or 6'-wide hoops can be created, for fabricating low tunnels that span one or two beds at at time.

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Row Cover

Greens for production under low tunnels

These transplanted greens are ready to be covered with a low tunnel.

When frost is predicted, the hoops are covered with row cover (Agribon+ AG-19 or heavier) to extend the crop into the fall. These porous "blankets" protect the crop from frost while allowing them to respire and self-ventilate as temperatures fluctuate throughout the day.

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Plastic Film

After a few frosts, and once the chance of warm days has diminished, a layer of 4-mil (100-micron)-thick greenhouse film can be laid overtop the row cover.

If perchance warm weather occurs after the addition of the plastic layer, you may need to manually regulate internal temperatures, ventilating the low tunnels by lifting their sides then lowering them again as temperatures drop.

In the dead of winter, the tunnels will effectively be sealed shut by the snow load on top.

Following the winter solstice, the tunnels may again need to be vented intermittently, to prevent overheating as days grow longer and warmer.

Once the danger of hard frost has passed, the plastic can be removed completely, with the row cover remaining in place to protect the crop until it is time for early-spring harvest.

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Next... Focus on Crops & Varieties for Winter Growing

Learn More

How to Set Up and Manage Your Quick Hoops Low Tunnels, excerpt from Eliot Coleman's Winter Harvest Handbook.

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