When deer roam into the Horticultural Research Center at the University of Minnesota Arboretum and chew on the ends of tree branches, they can set fruit-breeding efforts back by years.

To help prevent deer from making a buffet out of the center's orchards, which are home to a flagship apple-breeding program, the arboretum is constructing fences on the property's northern boundary.

Over the three decades he has done research at the center, Jim Luby said he has seen the local deer population expand with the area's suburbs, which push out predators and provide ample sources of food.

"They can just go down a row of small trees and do a lot of damage," said Luby, director of the U's fruit crops breeding project. Some of the center's new fencing is going up on recently acquired land, he said.

The additional fencing is part of a continual effort to keep deer out of the gardens, plant collections, orchards, prairies and wetlands on the university property in Chanhassen.

The project is being paid for with capital campaign funds, said Peter Moe, director of operations at the arboretum. The two fences will cover about 7,000 feet and will cost $88,400, he said.

University researchers have bred apples, grapes and other fruits at the center for more than a century. In this time, they have produced 27 varieties of apples, including the popular Honeycrisp and SweeTango.

Deer cause trouble for researchers year-round by disrupting fruit growth, said apple breeder David Bedford. This prevents scientists from taking measurements and making crosses.

"By eating the ends of the limbs … it changes the hormonal balance of those trees," he said. "It affects the tree's ability to bear fruit."

Without deer involved, it can take breeders anywhere from 20 to 30 years to develop a new variety of apple, Bedford said. Add deer into the mix, and it's another 10 years on top of that.

Researchers have used deer fences at the site for years and have found them to be the most effective way to keep deer away, he said. Though older electric fencing is still used at the center, newer fences are made of woven wire meshes, and have openings large enough to let smaller animals like wild turkeys through.

Along with safeguarding research, reducing the arboretum's deer population can help regenerate native trees and wetlands, Moe said, and increase the number of wildflowers.

When the arboretum put up a $260,000 fence along its southern boundary in 2013, it caused an outcry from residents living across the street, who felt it clashed with the location's natural aesthetic.

That kind of controversy shouldn't be an issue with the new fences, Moe said, because they're not next to residential areas.

Moe said the deer population has typically been around 40 to 50 animals. The southern fences brought that number down to about 25 deer this year, he said.

For researchers, managing the deer population is one way they can control how natural phenomena impact their work, Bedford said.

"This is just about the most humane way you can control an animal," he said.

Parker Lemke is a University of Minnesota student on assignment for the Star Tribune.