At a University of Minnesota orchard near its horticultural research center in Excelsior, beyond neat lines of apple trees, rows of vines grow up T-shaped trellises situated on a slight slope with partial shade.
In May, branches full of green leaves form a thickening canopy dotted with small white flowers that, by August and September, produce clusters of smooth, green berries about the size of a quarter.
Bob Guthrie is standing beneath the branches wearing a khaki-colored vest covered in pockets where he keeps black zip ties, bug spray, and other tools within quick reach. He interrupted his afternoon of collecting pollen to give an impromptu tour, which gave him the opportunity to talk about his favorite subject: kiwi berries.
As a volunteer with the university’s breeding program, Guthrie is the resident expert on this relatively unknown crop, whose name conjures an image of tropical fruit but that actually grow in cold climates throughout the world — including in Minnesota.
Inside the research center, Guthrie points down a hall, where poster-size images of the fruit breeding program’s biggest successes — including the Honeycrisp apple and the Frontenac grape — line the wall. It will take years, but someday Guthrie wants to hang a photo of a commercially viable kiwi berry there, too.
“I just see a lot of potential,” he said.
An unfamiliar yet intriguing crop
Guthrie started volunteering at the university in 1994, when Jim Luby, head of tree fruit and berry breeding and an old classmate from Purdue University, took Guthrie to the horticultural research center to see the kiwi berries growing on a single abandoned grape trellis.
With help from contacts around the country, he started building a collection of plant material here. Despite a full time job as a geologist for the Minnesota Department of Natural Resources, he became a student of the kiwi berry’s history, which includes quirky stories of old nursery catalogs that didn’t distinguish between male and female vines. Leaving out that important detail left many growers with infertile plants, and Guthrie believes that mistake is one of the reasons the fruit didn’t take off in the United States.
Kiwi berries have been the focus of backyard growers who mostly like the way they look — some varieties have leaves that turn white and pink to attract pollinators — but the country’s main kiwifruit production is concentrated in Oregon and California.
To Luby, kiwi berries are an “intriguing crop” that present interesting scientific questions. They’re a bit off the wall compared to other university breeding projects, but grants like those the U.S. Department of Agriculture gives out for specialty crop researchers to study new things helped Luby’s department put a little money toward investigating its commercial potential. That puts it in a similar position now that apples were in about 100 years ago, or wine grapes 40 years ago.
“For apples, I think it was a crop that earlier settlers in the state were certainly very familiar with in their heritage whether they came from the east coast. The challenge was finding ones that could grow here in our climate,” Luby said.
Kiwi berries, though, are “a little different because it’s a crop that’s not really widely known and so it’s going to be taking something that’s not familiar with people and try to get them familiar. People didn’t eat blackberries unless they were out in the wild and now they’re in the grocery store year-round. Kiwi berry is probably more like that.”
‘We’re definitely in the early days’
At the end of September, Seth Wannemuehler gathered the last samples he’d need from this year’s kiwi berry harvest, working his way through the same patch of vines Guthrie showed off months earlier and placing the crop into small plastic berry containers.
The university could afford to hire a dedicated person for the kiwi berry project after securing funding through a specialty crops grant, and Wannemuehler is a recent graduate with a master’s degree in applied sciences. His background includes biochemistry, microscopy, economics, outreach, and post-harvest handling, making him a perfect candidate to tackle the project.
From studying the chemistry of the fruit to surveying consumers about their interest to guiding future growers in when and how to harvest kiwi berries, there’s a lot to investigate, and little money to bring in other experts to help. “Obviously this is not a main focus for the breeding program,” Wannemuehler said.
Each new fruit variety is the product of decades of research on the fruit’s taste, texture and appearance, as well as the plant’s growth habits. Minnesota’s brutal winter temperatures and short summers offer strict parameters on what researchers can attempt to grow here. You won’t see Minnesota oranges.
But climate change is making new things possible in the state, Guthrie said. He suspects that’s one reason kiwi berries may stand a chance now more than a century ago.
For Luby, any new project starts with a question of taste. “Is this thing good to eat? Are people going to enjoy it?”
From there, the university must tackle the many technical questions. For example, the kiwi berry varieties they’re eyeing that may produce the right qualities once crossed – including flavor, cold-hardiness, and vigor – pose a significant genetic hurdle. One has two sets of genes and the other has six. That difference makes it challenging to cross them. In fact, it could take a decade, Wannemuehler said.
Then there are the logistics of scaling up production. It has taken about 20 years of growing grapes at commercial scale to answer to questions about yield, Luby said. “It does take some years to do this. It’s not something you can start the production line and two years later you’ve got it. We’re definitely in the early days.”