In 2006, Jenny Thull was taking a class on food and wine of the world at Le Cordon Bleu College of Culinary Arts when her instructor arranged for a field trip to see the vineyards at the University of Minnesota Arboretum.

John Thull was working that day. He’d been hired as a gardener at the Horticultural Research Center the year before when his boss, Peter Hemstad, said, “How about you give the tour this time? You can explain what we’re doing as well as I can.”

Thull gave the tour and made an immediate connection with one of the students. “It was one of those instant things,” says Jenny. “I just knew right away. Everybody thought we knew each other.”

A few weeks later, Jenny came back to volunteer with John. She spent the day twisting in earth anchors as they installed a new vineyard. That night, the workers were going bowling to celebrate a birthday, and John invited her along. So Jenny drove home, got cleaned up, then drove back for their first date.

Jenny had grown up in Woodbury, Minnesota, where her father worked as an engineer for 3M. He flew all over the world and brought home exotic wines for the family (including Jenny) to taste. In the 1990s, he came home from Argentina with a suitcase full of a wine no one had heard of. It was called Malbec.

After high school, Jenny went to the University of Wisconsin-Madison to study engineering like her dad. But she quickly realized it wasn’t for her. She joined the Air Force, where she worked in intelligence for a few years. But that wasn’t quite a fit either. When she got out, she started working in a restaurant and loved it. She worked every job in the place, even landing in management before getting her culinary degree at Le Cordon Bleu.

John grew up on a dairy farm in Stearns County, Minnesota, not far off I-94, in a part of the state where German was still widely spoken. Conversations at his dinner table were peppered with German words, and whenever someone got mad, the swear words were in Deutsche.

“If you had a farm implement shop there in the 1970s,” John says, “you had to know German because the old farmers would call you up and would not speak English.”

After getting his biology degree at University of Minnesota Duluth, John applied to the University of California, Davis, which has good enology and viticulture graduate programs. But his application was late and the program was full. So he made other plans: The Thulls still had relatives in Germany, so he went there and found an apprenticeship in a riesling vineyard.

After around two years in Europe, John came back to the U.S. in late 2004. When he did, he drove out to the Arboretum to see if he could volunteer in the Horticultural Research Center’s vineyard. He was told to come back in the spring when staff were pruning to see if he actually liked working there. Peter Hemstad was the grape breeder at the time.

“John is pretty much the perfect vineyard manager,” says Hemstad. “If you started with a blank sheet of paper and made a list of attributes you hope to find, he has every box checked. Hiring him was probably one of the best decisions I made in 30 years there.”

John had been in the vineyard about a year when Jenny showed up for her tour. After that, she came to volunteer every Monday. After finishing her culinary degree, she worked as a pastry chef at a golf club in Woodbury. Meanwhile she and John had started their own vineyard on John’s family farm.

Then, Jenny’s 2008, her job vanished with the financial crisis. It just so happened the vineyard had an opening. “They needed somebody to paint the posts,” Jenny recalls. She was hired on as a temporary seasonal worker, before coming on full time to help manage the vineyard.

“Jenny didn’t grow up as a farmer or a plant person,” Hemstad recalls. “But she adapted quickly and is an extremely dedicated, hard worker. They make a great team and are just a fantastic asset for the grape-breeding program. The University is lucky to have them.”

After John and Jenny started dating, they discovered they had many things in common: Their birthdays are just two weeks apart. They each had extensive German families. But most of all, they both love wine.

“When we first got together,” says John, “we started tasting and contrasting different bottles in the evening.”

The couple married in 2012, and wine has remained at the center: All their vacations revolve around wine-growing regions in California, Oregon, even Utah. And that love of wine has been at the center of their success at the Horticultural Research Center.

“We love wine so much,” says Jenny. “It’s such a huge part of our lives.”

A cold-hardy grape tradition

The story of the University’s grape program began in 1908, with an attempt to breed a cold-hardy table grape for juice and jelly. In the 1970s, researchers began collecting wild grapes that could be bred with European wine grapes, in hopes of breeding a vine that could survive Minnesota winters and make a drinkable wine. This was a challenge: Of the more than 10,000 named grape variety in the world, only a handful are amenable to Minnesota’s climate.

Developing a new grape vine can take anywhere from 15 to 20 years. In the late 1970s, a promising cross was made by a graduate student named Patrick Pierquet. After Hemstad started in 1985, he could see this vine was promising. Finally in 1996, it was deemed good enough to name and release.

Frontenac was the first blockbuster northern wine grape. It’s not an understatement to say it marked the birth of the entire northern wine industry, which now contributes millions of dollars to the state’s economy.

“It was very, very significant for the industry,” says Hemstad. “There’s no question that it’s become an important part of the overall tourism and agriculture industry in Minnesota. But also in Wisconsin and all the surrounding states, as well as New England and parts of Canada.”

Frontenac was followed by La Crescent in 2002, Marquette in 2006, Itasca in 2017, and Clarion in 2023, all of which the University licenses to vineyards to grow.

“The grape breeding program is very unusual,” says Hemstad. “If you look at a map of the U.S. and put a dot for each grape-breeding program, there aren’t many dots. And its reach is quite significant. Whenever we release a grape, you know it’s going to be planted across the northern states right away.”

Be the vine

Walking through the vineyard, it’s clear that one secret to the couple’s success is their deep understanding of the plants themselves. As John likes to say, you have to “be the vine.”

John explains, “I was sort of pulling that from Caddyshack, when Bill Murray says, ‘Be the ball.’”

“It is a really good mindset,” Jenny adds. “We meet a lot of people who want a really simple solution to growing their vines. They want to know how to prune them. They want it all to be the same. But you have to immerse yourself in the vine.”

“You have to live the season with the vine,” John says. “You have to think: How are those roots behaving? What are they feeling like when it’s too wet? What are the tops feeling like with a harsh winter or low humidity? You’re trying to think: How is that thing feeling? Just being the vine.”

Eventually, we drive over to the original vineyard block, where several vines from the 1970s still grow. Some are thriving; others are barely hanging on. Many have passed on to that great vineyard in the sky.

We walk down one row to see a vine that to me looks like any other. But it’s not. This is the one that started it all, the one that put Minnesota wine—and the Arboretum—on the map.

“That’s the original Frontenac,” Jenny says.

“We call it the mother vine of Frontenac,” says John.

“The cross was made in ’77,” he adds. “It probably got in the ground in ’78. And Jenny and I were born in ’79. So it’s probably a year older than us.”

Jenny takes a grape and puts it in her mouth.

“I think this grape, as it’s in people’s vineyards, has gotten better,” she says. “The wine they’re making from it is better than when they first planted it. I think there’s a richness to it now.”

I taste a grape. It tastes sweet and good. Standing next to the mother vine of Frontenac, I can imagine earth and sunshine. I can almost feel the rain, wind, and snow.

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