High tunnels help producers stretch out the growing season and save money
“High tunnels, which are also known as hoop houses, are basically a passive greenhouse, meaning they don’t require any energy inputs to operate them,” says University of Wyoming Extension Educator Jeff Edwards. “They also increase the growing season by a minimum of 30 days in the spring and up to at least 30 days in the fall.”
“High tunnels also allow producers the opportunity to start growing plants earlier, produce them longer and grow produce they normally would not be able to grow,” adds Edwards.
Edwards referred to a high tunnel UW built last year in Torrington that was capable of producing spinach all winter long. However, with the growth rate being so slow, they were only able to harvest the spinach twice during the winter.
“Most greenhouses require energy inputs, such as electricity, to either heat them in the winter time or cool them in the summer time,” describes Edwards, “so that’s a savings right there for producers.”
“There is research suggesting that for every square foot of production a producer has in a high tunnel, they can receive five to 10 dollars a square foot in sales directly,” says Edwards.
“Producers aren’t dealing with wind or hail, and they are protecting the crops from frost with the use of high tunnels. Those seem to be the big detriments to production in our area,” explains Edwards.
Other produce Edwards cites as growing well in high tunnels in Wyoming are tomatoes, peppers, kale, melons, cucumbers, artichokes, eggplant, cabbage, sweet corn, flowers and lots of salad greens.
“The ceiling ribs of high tunnels are usually made out of Schedule 40 PVC pipe while the rest of the high tunnel is constructed with lumber,” notes Edwards.
“The skin for the high tunnels is a woven polyethylene product that is able to diffuse light as it comes into the structure,” explains Edwards. “The light then bounces around inside the high tunnel. There’s some data to suggest plants are getting light from all angles, and it makes them more efficient at photosynthesis.”
He continues, “When inside a high tunnel, there are no shadows or shading to worry about.”
The skin of high tunnels goes on the outside of the structure and is available through two companies in the U.S. – J and M Industries located in Ponchatoula, La. and at Northern Greenhouse sales in Neche, N.D.
On average, the skins last between five to six years.
Raised beds can also be put into high tunnels to help individuals who have mobility problems. There is no growing difference with growing produce in the ground versus growing in raised beds, other than the loss of production space with raised beds.
Orientation and challenges
“There’s a lot of information out there on whether or not high tunnels should be oriented north and south or east and west,” states Edwards. “If the high tunnels are covered with one of these woven polyethylene skins, that’s not as important for growing as ventilation is.”
He adds, “High tunnels get really hot in the summer time, and producers have to be able to open the doors or roll up the sides to vent out the heat.”
“Vine crops have a tendency to get more diseases than other produce. When growing in a high tunnel environment, there is an increase of humidity, so a powdering mildew can become a problem,” comments Edwards.
Along with humidity, Edwards advises producers to be on the lookout for insects collecting within the high tunnels.
“As long as producers are watching their crops, managing them correctly, looking for problems and taking care of them immediately, there shouldn’t be any trouble,” says Edwards.
High tunnel designs
The high tunnel designs UW has been building in Wyoming can be found at wyomingextension.org/whhin, and they are less expensive than kits for high tunnels that can be found on the internet.
“Our designs seem to hold up a little bit better than kits, as well, as far as not blowing away in the wind,” describes Edwards. “Because our designs are so inexpensive to build, a producer can pay off their structure in a year.”
High tunnels are relatively inexpensive to construct. The cost to construct them is $3.25 to $3.30 a square foot.
Sizes vary for high tunnels from 12 feet by 12 feet to 24 feet by 72 feet.
Selecting a site
“Producers should select a site that has water, won’t need electricity and is level. However, a producer may want electricity out to it,” states Edwards. “In some instances, a building permit may be required. High tunnels are considered a temporary building and can be moved if necessary.”
Edwards warns, “In some counties in Wyoming, high tunnels are taxed. In others, they are not.”
Grants are available for producers to help offset some of the costs for high tunnels through the Wyoming Department of Agriculture and the Natural Resources Conservation Service (NRCS).
Edwards hosts workshops on building high tunnels and encourages people to contact him if they have any questions.