Extending Wisconsin’s Raspberry Season

Professor Rebecca Harbut

Professor Rebecca Harbut, and student Michael Muehlbauer check raspberries growing in a 14-foot high tunnel, where they’re working to lengthen Wisconsin’s growing season.

When it comes to growing fruit crops in Wisconsin, high tunnels—which most of us would see as tall hoop houses—are becoming all the rage. Hundreds have gone up thanks to a federal cost-sharing program, and they promise to conserve resources and extend growing seasons for customer favorites such as raspberries.

Fruit growers, however, don’t know how plants’ nutritional needs change if they’re grown in a 14-foot high tunnel. A new high tunnel, paid for through the University of Wisconsin-Madison’s College of Agricultural and Life Sciences Annual Fund, makes it possible for Rebecca Harbut, an assistant professor of horticulture and a University of Wisconsin Extension fruit crop specialist, to find needed answers. Local growers helped build the tunnel last spring at the West Madison Agricultural Research Station.

Grants don’t generally cover infrastructure costs, Harbut said. But she’ll be able to leverage having a high tunnel to secure grants to improve fruit production.

“We really appreciate the flexibility that the Annual Fund allows us to invest money where we need it most,” Dean Kathryn VandenBosch said. Not only does the Annual Fund allow the College to be nimble in pursuing developing opportunities or addressing issues; it also allows the dean to attract other dollars.

Giving to the annual fund is about trusting that the funds will be used to address the College’s greatest needs, said professor emeritus Allan Bringe, a regular Annual Fund donor. Instead of designating his gift for a particular use, he believes the College will know how to best use it.

Harbut is working with fall-bearing plants that begin producing in mid- to late-August and continue through frost. A high tunnel can extend the season into November, she said. “It’s really a whole new market that’s available and extends the fresh fruit season in Wisconsin.”

The trial looks at how to best grow raspberries with no rainfall, higher temperatures and a longer season. The demands on the plant are higher, Harbut said, and she’s studying how to maximize yields with minimum added nutrients. The high tunnel also opens the door to study production of dwarf sweet cherry trees and whether strawberries can be grown vertically to maximize production in a small space. All of that work will be helpful for urban agriculture as well, Harbut said.