— Dennis Robertson was visiting his wife’s hometown of Medicine Hat, in Alberta, Canada, when he picked up a brochure for the local “Heritage Tree Trail.” There were seven trees on the trail. They drove around the city tracking them down, one by one. There was giant white pine planted by a famous horticulturalist. There was the first cottonwood planted in the city (in 1888). There was a dragon spruce, native to China, that grew well in Medicine Hat’s environment. There were other trees of note.

When Robertson got home, it occurred to the retired ophthalmologist that Lake City had some pretty good trees, too, and that those trees had some history. For starters, it had a park filled with unusual species from the Jewell Nursery, which was founded in 1868 and became the largest landscape nursery in the country, if not the world. A heritage tree trail, he thought, would be a great way not only to help people learn about those trees but serve as a bridge to the past. As far as he knew, such a trail also would be a first in Minnesota.

The idea of heritage trees has been gaining in popularity around the world, even if what constitutes “heritage” is open to debate. Singapore has a heritage tree trail. So does London. Portland, Ore., produces an 80-page booklet of heritage trees, most which are just big, old trees. San Luis Obispo, Calif., has a heritage tree app. Even Minneapolis has a program to identify the city’s heritage trees, though of its 86 specimens only two are “historically or culturally significant.” (One of those two, the “ancient oak,” died in 2010.)

Robertson, 81, wanted something substantive, alive. His idea had the support of the Lake City Historical Society. He also consulted with local arborist Katie Himanga, who pointed him toward some specific trees in Patton Park, including a Douglas fir she says is likely the largest in the state, and some oak that were there before European settlers arrived.

“There are a couple trees in that park that have been witness to the entire history of this city, right back to when the indigenous people were the inhabitants,” Himanga said. “I suspect the oaks are in the 170- to 200-year range.”

Robertson also picked out some massive cottonwoods along the riverfront that were more than 100 years old.

“The river looks pretty much the same,” Robertson said, standing next to one. “Ninety-five years ago, this tree was here, witnessing Ralph Samuelson become the first person to ski on water. Right here! You can just imagine the people along the shore as Samuelson went by.”

We often take them for granted, but Minnesota is embarrassingly rich in trees. According to the U.S. Department of Agriculture, there are 14.7 billion in Minnesota (up from 13.1 billion in 2008). And apart from trees’ historical role, many people are beginning to see them in a new light.

“There was a really interesting study in the Midwest, which looked at the health effects of these communities that have lost so many ash trees,” said Florence Williams. “In neighborhoods where these tree had been decimated, people showed signs of an increase in cardiovascular disease.”

Williams is author of “The Nature Fix: Why Nature Makes Us Happier, Healthier, and More Creative,” which digs into research around the world keying on the power of the outdoors.

Large-scale studies in Europe have found that people who live near green spaces have a lower incidence of heart disease, cancer and hypertension.

No one knows quite why this is, but Williams pointed to a clue in findings by Japanese researchers that exposure to a forest can increase the number of disease-fighting T-cells in our immune system. Even just looking at trees causes our brain to produce more alpha waves, which are associated with calm, alertness and creativity.

“There’s something soothing and comfortable to our perceptual system about viewing scenes from nature,” Williams said, “which makes sense because our brain evolved to perceive input from the natural world. So when we go back to it, we kind of just relax a little.”

Tangible links to history

For Robertson, getting people outside to look at the trees was one of his goals. But another went back a little more than 70 years to a time when he was a young boy in St. Paul at the science museum. There, he saw a crosscut section of a giant Douglas fir from Washington state that had been nearly 600 years old and stood 300 feet. You could count its rings back to 1431, when Joan of Arc was burned at the stake, to 1620 when the first Pilgrims landed on Cape Cod, to 1865 when the Civil War ended, all of which were marked. These events were so far removed as to seem unreal. But here, in this tree, was a physical connection to the past, a tangible link to history.

As he began researching the trees on his Heritage Tree Trail, Robertson’s mind would return to that Douglas fir and to that sense of wonder and connection it aroused. That, as much as anything, was what he hoped to pass on to others who followed the trail.

“It’s just a sampling, but these trees all have some meaning,” he said. “They all relate to the community in some way.”

Frank Bures is a freelance writer from Minneapolis.