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The legacy of botanist Walter Cottam transformed U campus into a living laboratory

How the university became Utah's official arboretum, home to 9,600 trees on its main campus, featuring at least 250 species from around the world.

Back in the 1930s, University of Utah administrators had a plan for a natural gully that ran past the then-new Thomas Building (now housing the Crocker Science Center) south of Presidents Circle. That proposal was to fill it and and stick more buildings there.

A portrait of Walter Cottam by painter Alvin Gittins.

Botany professor Walter Cottam had a different idea for the spot. How about a botanical feature filled with exotic trees? This vision for what became known as Cottam’s Gulch somehow prevailed, and ultimately proliferated around the U where Cottam and colleagues went on a decades-long tree-planting spree.

Thanks to those efforts, the Utah Legislature in 1961 designated the booming campus as the state’s official arboretum, to “provide resources and facilities for cultivating a greater knowledge and public appreciation for the trees and plants around us, as well as those growing in remote sections of the country and world.”

More than 60 years later, main campus is home to 9,600 trees representing 250 species and many more different varieties within species. With Arbor Day upon us (April 26), now is the time to tour the campus arboretum with trees beginning to leaf and blossom.

Besides serving as an academic institution, the U campus is also a vast arboretum with thousands of trees.

Bring a smartphone so you can scan the QR codes found on placards attached to about 100 trees, most of them within or near Presidents Circle.

Suzie Middleton, a certified arborist and GIS specialist with Facilities Management, catalogued and calibrated the campus trees and developed the web pages for the specific tree species associated with each placard.

Her pick for the U’s Most Magnificent Tree is the massive Japanese zelkova on the south edge of Cottam’s Gulch.

The Japanese zelkova remains on the edge of Cottam’s Gulch, immediately to the north of the Applied Science building under construction in 2024. The banner photo, shot by Suzie Middleton, shows the zelkova with its fall foliage. Photo credit: Brian Maffly

“This tree is amazing in the fall. It has this gold color. It is just bright gold. And then when the sun hits it, it illuminates. Just incredible,” she said during a recent visit to pay her respects to the 44-inch caliper tree Cottam planted 90 years ago. “And it has this beautiful exfoliating bark and these bright orange bumps. These are called lenticels. They help with oxygen and carbon dioxide flow in and out of the trunk.”

The tour Middleton mapped is a great way to learn about these trees while wandering the campus.

Also worth visiting is Red Butte Garden, the U’s botanical paradise in the foothills just east of campus. Friday is free admission for the garden’s Arbor Day Celebration and related activities, including a Tree of Life children’s event hosted by the Consulate of Mexico and led by Salt Lake City artist Vicente Martinez.

Red Butte itself is an arboretum with about 2,000 trees within its 21-acre fenced area, representing 450 taxa according to the garden’s arborist Charlie Perington.

Suzie Middleton visits Cottam’s Gulch in April 2024. Photo credit: Brian Maffly

Cottam’s Gulch, the arboretum’s birthplace, is now hemmed by the Crocker Science Center, built a decade ago and the Applied Science building rising immediately to the south.

It survives mostly intact and still harbors some of the campus’s finest trees, according to Sue Pope, the U’s open space manager. Among the state champions found here are a hedge maple, Lawson falsecypress, Japanese pagoda tree and the zelkova, whose canopy spreads so far it almost touches the science building under construction beside the gulch.

Gone is a giant Sequoia which was compromised by underground utility lines installed to support the Crocker construction. The loss of that historic tree and others helped spur policy changes that require planners to explore ways to minimize tree loss when projects are planned.

Campus construction remains the leading cause of trees’ demise.

The 110-foot-tall giant sequoia that once towered over Cottam’s Gulch. It came down in 2016. Photo credit: Suzie Middleton

“Donors want buildings and students need growth in education. It’s been an ongoing battle,” Pope said. “As those utilities get shallower, it’s more difficult to grow a tree that is competing with that infrastructure. We have tunnels that carry electrical ductwork and high temps. The university’s new master plan will hopefully better identify where we can plant to give trees more longevity.”

Now two trees must be planted for every tree lost to construction. But that rule hardly makes up for the canopy cover lost when a mature tree comes down.

“We have huge tree canopy loss over the last 10 years,” Middleton said. “We’re trying to decrease the loss on campus because of the sustainability of having that tree canopy on campus.”

Besides making campus a more pleasant place, large trees help the ground retain water, support habitat for animals and cool adjacent buildings.

A co-founder of the Nature Conservancy, Cottam may be best remembered for creating the U arboretum and for warning against the ecological harm caused by overgrazing, which stirred controversy in 1947 and nearly got him fired.

But he left a big mark as a beloved educator and a distinguished botanist who won accolades for his research on hybridizing oaks.  The Quercus genus of oak features some 500 species, both evergreen and deciduous.

Following his retirement in 1961, Cottam experimented with Utah’s native gambel oaks, crossing them with live oak and other species. The campus itself became his laboratory as he, Richard Hildreth, Red Butte’s first director, and students planted the resulting hybrids around campus where these unusual oaks still stump the most perspicacious tree connoisseurs.

“As a certified arborist identifying these trees on campus, you’re like, ‘What is this? Am I going crazy?’” Middleton said. “I have no idea what this tree is, and come to find out, it’s all these hybrids that Dr. Cottam has placed around campus.”

Cottam died in 1988 at age 94. Three stands of his oaks remain today, including—you guessed it—Cottam’s Grove, west of the Red Butte Amphitheater, where 141 mature hybrid oaks are still growing, a living testament to the botanist’s legacy.