The nearly 8,000 trees of the University of Arizona campus reflect more than a century of scientific research on appropriate species for semi-arid climates and evolving tastes in landscape design.
Some, like the groves of olive trees lining the western edge of campus along North Park Avenue, might not be planted today because of their water use and allergenic pollen. But they are valued for their history as well as their beauty and shade.
They are part of a National Historic District and a "living legacy" of the UA's Campus Arboretum, established 10 years ago to preserve and enhance that legacy.
They are also part of a very valuable investment. A recent "tree assessment" performed by undergraduate students for the Arboretum, set an overall replacement value of $28.2 million for the campus trees, In addition, the trees supply a $272,997 annual benefit by reducing utility costs, sequestering carbon and capturing storm water that might otherwise run off into the streets and sewers.
Newer plantings, like those done in conjunction with student research into water harvesting at the UA Visitor Center at East University Boulevard and North Euclid Avenue, are part of a contemporary push for a more sustainable environment that is taking the UA Campus Arboretum back to its desert roots.
One of the current goals is to expand the number of species on campus that are endemic to the Tucson Basin and also to plant new cultivars being developed for the region, said Arboretum Director Tanya Quist.
Such initiatives represent the Arboretum's commitment to research and outreach, she said.
The Arboretum, part of the Cooperative Extension arm of the UA's College of Agriculture and Life Sciences, has a mandate for applied research and education, she said.
The university's plantings began with an early emphasis on Sonoran Desert varieties.
Early photos of the UA campus show a few buildings, surrounded by a forest of 600 varieties of cacti and succulents - a garden begun in 1891 by UA professor James Toumey and expanded under University President Homer Shantz, a botanist who also added an oasis to the president's residence on campus. That building is gone but the pond, near North Park Avenue and East Second Street, still hosts turtles, bullfrogs and the occasional blue heron.
Over the years, the university planted varieties of crops on campus, including crop trees such as olives, date palms and citrus. It experimented with semi-arid species from the Mediterranean, Australia and Central and South America.
Warren Jones, a professor of landscape architecture, brought hundreds of new varieties from around the world to campus from the 1960s to the 1980s. Many of them grew to be the largest, and in some cases, the only specimens of their type in the United States.
The current landscape trend favors a native palette, said UA planner Grant McCormick but also embraces the historical notions of shady groves and greenbelts on the campus edge.
The recent greening of a buffer for the Jefferson Park neighborhood on the north side of the UA's medical campus is a nod toward the greenbelt of olive trees and other imported species along the west edge of campus. "The desire is really to create that same shady feeling that is conducive to gatherings of people, but to do so with native species."
McCormick said he envisions someday creating a shady tree-lined street or walkway on campus with ironwoods instead of olive trees.
Quist said research on landscape plants is an important part of her college's land-grant mission, and an often overlooked one.
Our knowledge of growing food crops is "precise, technical and scientific," she said.
"In our day, horticulture is grossly undervalued."
With 80 percent of Arizonans living in large metro areas, we need to pay more attention to urban landscape, she said. "We have a long way to go in improving our precision in how we grow and manage our landscapes," she said.
Take a virtual tour of the UA Campus Arboretum or sign up for an actual one at: arboretum.arizona.edu/outreach
Contact reporter Tom Beal at email@example.com or 573-4158