Four-season gardening with low tunnels
Fall is officially here and the temperatures are getting noticeably cooler. The first frost in Johnson County usually comes around October 23rd which is when most annual fruit and veg plantings will succumb to the cold. If you’re like me you’ve probably already started to yank out some of the more tender summer crops that you had cared so dearly for over the last few months. And although some hardy plants (e.g. leafy greens, broccoli, root crops) will survive a few cold snaps, their days are numbered once exposed to hard freezes.
But if you’re committed to growing beyond the normal limits of our climate, there are many season extension techniques that will support plant growth almost year-round. One of the most simple and cost effective methods is building your very own “low tunnel.” These temporary structures rely mainly on evenly spaced arch shaped wire/pipe frames, built from bent metal or plastic covered with tightly fastened clear plastic sheeting for capturing maximum heat. The same structures can also be used with light weight frost blankets, shade cloths and insect netting.
Commercial growers in the Midwest have increasingly adopted similar albeit larger structures known as high tunnels or hoop houses, coveted for their ability to create microclimates, specifically warmer air and soil temperatures. More broadly, both low and high tunnels, create a “controlled environment” where a grower can protect plants from weather, pests and disease. In contrast to greenhouses, tunnels do not require a permanent foundation and the crops inside are often grown in ground. These simple structures rely largely on passive solar heating and generally cost less to construct.
A three-season high tunnel at the K-State Olathe Horticulture Center with tomatoes, cucumbers and squash inside. The plastic covering on three-season tunnels is removed before winter each year.