Securing Covers on Low Tunnels


| 12/11/2014 9:32:00 AM


Tags: winter gardening, season extension, Cindy Conner, Virginia,

 low tunnel-fall greens

Building low tunnels that are about 30 inches tall to protect your crops through weather that is outside of their comfort zone is fairly easy to do using plastic pipe and plastic sheeting. You will find directions for this at Homeplace Earth. The tricky part is securing the covers. I have seen directions to make the cover with enough plastic sheeting on each end to draw it together to tie to a post in the ground. Sometimes the design calls for simply gathering the extra and holding it down with a cement block. The sides in that design are held down with rocks or boards or buried in the ground. The way I see it, the only use for a low tunnel made that way is if for crops in a bed that wouldn’t need vented, checked on, or harvested for weeks t a time. There is no easy way to access the plants.

If there is a ridge pole, as my design has, snow and ice usually slide off or can be brushed off easily without damage. In fact, some snow on the cover provides insulation in severe weather. However, since it also prevents light from getting through, it is good to get the snow off after a day or two.

Wind, on the other hand, is quite another thing and is the major problem for low tunnel covers. It will pull the sides right out from under the rocks, boards, soil, or whatever you have held it down with. Besides leaving your plants uncovered, all that blowing around wears on the plastic sheeting. I solve that problem by using a cord over the top to keep the cover grounded.

The cord is tied to a screw eye at the base of the arches at each end of the tunnel. It goes over the ridge pole to the other side of the next arch, passing through the screw eye at the base of that arch, proceeding across the ridge pole to the other side of the next arch, and so on. A bungee cord can be used at one of the end arches between the cord and the screw eye to provide tension.

Using the cord eliminates the need for anything else to hold the sides down. The plastic sheeting can be lifted for harvesting or tending the plants and pulled back down when done. The cover still needs to be secured to the end arches and this can be done using garden clips, sometimes called snap clamps. Here in Virginia in zone 7 it is an advantage to be able to have the ends open, so I only leave a few inches overhang. I cut a separate piece of plastic sheeting for each end in the shape of the arch. When needed, it attaches to the arch with the same clip, holding both pieces of plastic secure at the same time. The top of the end piece can be left unattached to provide some venting. When not needed, these end pieces can be folded and tucked inside the tunnel with the plants.

mike63denver
12/12/2014 9:43:20 AM

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