DIY low tunnel: a way to extend growing season

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A low tunnel allows growers to plant earlier in spring, and produce longer in fall. It creates a microclimate around plants, protecting them from frost, wind and other harsh weather elements.

Low tunnels are mini hoop houses. You can make one with PVC pipe and a few materials from your local hardware store. Frame materials cost less than $50 for a 5’ x 10’ low tunnel. This plan for a DIY low tunnel takes a few short hours, you can have one up in a single afternoon! [DIY Low Tunnel Blueprint]

Covering options: fabric or film

Row cover fabric is lightweight and breathable. It allows sunlight and some moisture to pass through. Agribon row covers come in four grades: AG-19, AG-30, AG-50, AG-70. AG-19 protects plants to 28°F and provides 85% light transmission. AG-70 protects plants below 24°F and provides 30% light transmission. My source is Johnny’s Selected Seed.

Film is plastic. Thickness ranges 1 to 6 MIL and provide 88% light transmission. Film retains more heat and humidity than fabric. Film covered low tunnels require ventilation. Open access side during the day or add slit perforations to ventilate. I purchase film from Grower’s Supply.

DIY low tunnel

Materials:

  • Fabric or film
  • 11 ea. 10’ ¾” PVC pipes
  • 4 ea. ¾” PVC 3-way fittings
  • 4 ea. ¾” PVC 4-way fittings
  • 6 ea. ¾” PVC adapter fittings
  • 6 ea. ¾” PVC saddle tee fittings
  • PVC primer and cement
  • 100 grit sandpaper

Directions:

  1. Use a miter or hand saw to cut PVC pipe for frame: 6 pieces 38.5” and 4 pieces 58”.
  2. Prep pipe ends and insides of fittings by lightly sanding.
  3. Apply purple primer to pipe ends and inside of fittings. Apply cement to pipe and fitting, secure with a turning motion. Hold for 30 seconds. Repeat for all frame fittings.
  4. Bend hoops into place.
  5. Screw 6 adapters into 6 saddle tees.
  6. Measure length of tunnel. Cut three remaining PVC pipes to length.
  7. Prime and cement an adapted saddle on each end of 6 pipes (see picture).
  8. Set pipes in place. Level and secure with wire (see picture)
  9. Set low-tunnel in desired location.
  10. Apply cover. Pull taut. Bury three sides of cover under soil, leaving one end open for access.

TIPS:

  • For adequate pollination, remove fabric or film when first flowers appear in spring, or when temperature has warmed.
  • In late fall you can add heat by filling empty milk jugs or buckets with water and placing near plants. Water acts as a heat reservoir, increasing temperature inside of the tunnel.
  • Hang heat emitting lights from hoops to give plants extra heat and light.

Cool-season crops for low tunnels

  • Lettuces
  • Arugula
  • Spinach
  • Kale
  • Bok Choi
  • Swiss Chard
  • Beet greens
  • Mache

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