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
- 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
- Use a miter or hand saw to cut PVC pipe for frame: 6 pieces 38.5” and 4 pieces 58”.
- Prep pipe ends and insides of fittings by lightly sanding.
- 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.
- Bend hoops into place.
- Screw 6 adapters into 6 saddle tees.
- Measure length of tunnel. Cut three remaining PVC pipes to length.
- Prime and cement an adapted saddle on each end of 6 pipes (see picture).
- Set pipes in place. Level and secure with wire (see picture)
- Set low-tunnel in desired location.
- Apply cover. Pull taut. Bury three sides of cover under soil, leaving one end open for access.
- 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
- Bok Choi
- Swiss Chard
- Beet greens
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