Before World War II, Iowa ranked among the top apple-producing states in the country. Today, researchers at Iowa State University are working to bring that legacy back, using modern orchard systems that help growers produce more fruit on less land.
“It’s an orchard packed with more than just fruit,” says Suzanne Slack, assistant professor of horticulture at Iowa State. “This orchard has rows of research — with each tree bearing lessons on the best way to grow apples in the state.”
Building on a Storied Apple History
Iowa has a long relationship with apples, and Slack wants to see that history blossom again.
“Iowa, like I said, has a rich history of producing apples,” Slack explains. “Before World War II, we were one of the top apple-producing states in the nation, true story, and we wanted to see what we could do to help bring back some apple production in Iowa.”
Where Slack stands isn’t just any orchard. It’s a research station that’s been part of Iowa State since the 1960s, founded by renowned apple breeder Spencer Beach.
“He developed quite a few different apple cultivars that we still eat today, like Cortland apples are one of his most favorite ones, or Chieftain, which are the yellow ones behind us,” Slack says. “We’ve had a legacy of apples in Iowa ever since.”
A Modern Orchard for a Modern Era
Slack joined Iowa State in 2021 with a clear mission — to help Iowa growers produce more apples from every tree. Her latest project is a 2-year-old orchard that looks very different from traditional Iowa orchards.
“This orchard here was planted in ’23, so it’s 2 years old,” Slack says. “As you can see, it’s full of apples. The one behind us is a Blondie — aptly named — apple, very cute. And what this is, it’s called a high-density trellising system.”
The design, known as a modified super spindle system, is common in places like Washington state and the Northeast — but rare in Iowa.
“Basically, what we’re doing is we are trying out some of the Midwest heritage apples, or apples that people expect to find in Iowa, on this system to see if they can produce apples at the same rate as a larger tree,” Slack explains.
High-Density Systems: Doing More with Less
Across Iowa, about 300 apple varieties are grown by nearly 500 growers. Slack and her team hope their research will help those growers decide whether high-density planting can work in the Midwest.
“It’s easier to pick, easier to manage, it’s easier to spray, you have less disease problems, you get actually more apples faster,” Slack says. “An apple tree, if you plant it like a standard one, it could take five to six years to make your money back. You’ll make your money back pretty quickly on this one, even with the added cost of the trellis.”
And this orchard isn’t even planted at full density.
“You can actually plant a tree in between every single one of these for 18-inch spacing, like a tomato,” she says.
The trees are pruned constantly to stay compact and productive.
“These branches actually are pruned in a renewal style, so every branch you see with an apple on it is eventually going to be removed,” Slack explains. “We don’t have any permanent scaffolding. The only thing that’s actually permanent is the stem or the main leader of the tree, and the way we can keep them small is we’re just constantly doing pruning on them.”
Finding What Works in Iowa
Not every variety adapts equally well to the trellis system.
“Honeycrisp and Gala love this system of growing,” Slack says. “They make their apples on spurs — so the branch comes out, then they make their little spurs and you see these big clusters of apples. Easy to pick, it’s great. They can make a lot of apples in a little space.”
Others, however, don’t perform as well.
“Granny Smith is probably the most popular household name that doesn’t like this system,” Slack says. “It’s because they make their apples actually on the tips of the branches, and I just said we cut all the branches off. We do all this renewal pruning on them, so we’re actually removing a lot of our fruit whenever we try to grow them on this system.”
A Future for Iowa’s Apple Growers
For Slack, this research isn’t just about science; it’s about creating opportunity for more Iowa growers.
“I hope that they can get more bang for their buck,” Slack says. “They can have apples, people can pick them, they can sell them. They can also reduce their space, have less labor costs, less pesticide costs. And I think it could make it more commercially viable for more folks in the state.”
