Overwintering in Low Tunnels
A low tunnel is a row of hoops (ours are bent with hoop bender tools) set over the crops you plan to carry through winter. The hoops get a layer of row coverfirst, and a sheet of plastic film goes over that as deep winter approaches.
Hoops
Benders let you build your own high or low tunnels.
A low tunnel planted with overwintering onions.
Our hoop benders are made for shaping hoops from bent steel conduit (electrical metallic tubing, or EMT). In our experience, EMT hoops hold up under heavy winter snow, while wire or PVC hoops often don't.
Depending on the bender, you can make hoops 3', 4' or 6' wide to cover one bed or two.
Row Cover
Transplanted greens ready for their low tunnel.
When frost is in the forecast, cover the hoops with row cover (AG-19 weight or heavier) to carry the crop into fall. The breathable fabric shields plants from frost while letting them respire and vent naturally as temperatures swing during the day.
Plastic Film
After several frosts, once warm days are unlikely, lay a sheet of 4-mil (100-micron) greenhouse plastic over the row cover.
If a warm spell arrives after the plastic is on, you may need to vent by hand, lifting the sides of the tunnel and lowering them again as it cools.
In midwinter, snow on top will usually seal the tunnels closed.
After the winter solstice, as days lengthen and warm, you may again need to vent now and then to keep the tunnels from overheating.
When hard frosts are over, remove the plastic entirely and leave the row cover on to protect the crop until the early-spring harvest.
Next
- Winter growing guide, part 4: planting dates for winter harvest
- Winter growing guide, part 5: planting dates for overwintering
- Winter growing guide, part 6: crops and varieties for winter
More Resources
- Setting up and managing low tunnels, based on methods from Eliot Coleman's Winter Harvest Handbook
- Winter growing guide • Printable PDF, 10 pages
- Growing overwintered onions from seed • Article
- Overwintering Flowers • Article
- Winter tunnel radishes • Article
