Greenhouses aren’t the only great cover-ups for gardeners determined to extend their growing seasons.
low tunnels and caterpillar tunnels work well, too. Also known as hoop houses or row covers, the tunnels consist of U-shaped metal or PVC ribs draped by thin, plastic sheets. (PVC, or polyvinyl chloride, is what the white plastic tubes in the plumbing aisle of your favorite hardware store are made of. They come in different diameters with different degrees of flexibility.)
All of these shelters help control insects and boost yields, and when fall rolls around, they help provide shade for sun-sensitive crops.
Why build hoop houses rather than more traditional greenhouses? Primarily because they don’t need artificial heat when seasonal temperatures drop.
Greenhouses are often cost-prohibitive, said Dan Phelps, program coordinator and specialty crop specialist with the Kansas Rural Center in Whiting. “You have to heat these structures all winter long and that usually means fuel costs. With hoop houses, passive solar heating is enough to grow crops on both sides of the calendar.”
High tunnels and many of the caterpillar tunnels are tall enough to walk under. They resemble poly-covered Quonset huts linked end-to-end, or caterpillars.
“That’s a big plus, especially in rainy locations,” Phelps said. “You’re able to plant, harvest and cultivate even if conditions are wet outdoors.”
The shelters help professional growers and urban farmers because soggy or frozen soils can delay planting by several weeks in early spring. “But that’s not a problem (when growing) under high tunnels,” Phelps said.
Along with , high tunnels can double the size of harvests because they thwart hail and other blemishes.
High tunnels are a relatively new development for home gardeners in North America, but it’s expected they’ll soon become popular, said Cary Rivard, director of Kansas State University’s Olathe Horticulture Research and Extension Center.
“One of the things that has really helped open up this option is that the industry is starting to make small kits that can withstand high wind conditions, and there are some homemade options available,” Rivard said.
But there are a few things to keep in mind. First, the smaller the tunnel, the less thermal mass it contains, Rivard said. That means it will heat up — and cool down — more rapidly.
“So if they are building very small tunnels, they are going to need to be able to ventilate them really well in the summer using tall sidewalls and well-ventilated end walls,” he said. “Similarly, during the wintertime, a small tunnel will cool off very quickly.”
Hoop houses vary in type and size, but their sidewalls often are 4 to 6 feet high, topped by rounded rooflines. The hoops are spaced more closely together for strength in areas that get heavy snow.
Caterpillar houses are narrower and barely tall enough for gardeners to stand erect in.
And low tunnels are even smaller — generally around 2 feet high. Low tunnels are a great way to get cold-season crops like greens and certain herbs started earlier than you might otherwise be able to.
