With snow piling up in Northwest Iowa, many of us miss the wonders of our summer gardens. However, your garden can continue well into winter, or start earlier in the spring with the use of a low tunnel!
Creating a low tunnel in your home garden can extend the growing season for many of your cool season plants such as lettuce or spinach. The tunnels are beneficial during early spring to get plants outside earlier for a quicker maturing time. Low tunnels may sound overwhelming, especially since they are often discussed in commercial gardening, but they can be simple and helpful for the everyday gardener!
Low tunnels are a non-permanent structure that can be removed during the summertime. The tunnel frame can be anywhere from 2’ to 5’ in height depending on the plants growing under the tunnels. The frame of the tunnel, or hoop support, can be created out of a variety of materials from metal to plastic, with a spunbond polyethylene (poly) material to cover. Metal ribs, or thick metal wiring, can work as a great support. PVC piping is another alternative that you can use instead of metal, but will struggle in the heavy winds more than a stronger metal rib. The material will need to be bent into a hoop shape to create the tunnel structure. The poly materials come in a variety of weights that can provide an additional 2-8 degrees of warmth under the low tunnel. The lighter the material, the more sunlight will penetrate through to the plants. The heavier material will offer better protection against frost, which is extremely helpful if you are trying to start plants earlier in the spring, or extend them into the colder months. It all depends on your preference of materials. Once the poly cover is draped over the hoop supports, it is important to clip the poly material onto the supports and weigh down the edges of the cover with some type of weight to make sure the material stays in place. You can use anything from cement blocks to soil. As long as it is something that won’t fly away!
In addition to extending your growing season, a low tunnel also acts as an insect barrier. This is especially useful if you battle with cucumber beetles in your garden. However, it is important to remove the cover once the plants begin to flower to allow pollinators access to the plants. You must also remove the cover during the summer to release trapped heat so that the plants don’t get damaged.
This is a fun project to start planning for your garden while waiting for the growing season to return! For more information on how to build a low tunnel, view Extension Commercial Horticulturist Joe Hannan’s YouTube video on UKNOW How-to Videos (https://www.youtube.com/watch?v=4U7e4VTJ8-o).
Iowa State University Extension and Outreach—Region 5