These days, professors on campus use the trees to teach students about art, science and the environment, he said. Tuesday, at least one student used the sunny base of a tree as a place to lean back with a book.

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The Montana Legislature designated the Missoula campus as the official State of Montana Arboretum in 1991 to “facilitate the scientific study and public exhibition of many species of trees and shrubs.” Most of the trees aren't a century old, although the giant red oak could be as old as 90 years, Goodburn said.

In the arboretum's 25th year, the trees' caretakers have big plans for the prized forest, and Goodburn credits UM gardener and committee member Kelly Chadwick as the top caretaker.

The Montana Department of Natural Resources and Conservation granted the arboretum $6,000, and a private donor made a gift of $25,000, with funds to help the arboretum grow in number of trees and in visibility, Goodburn said.

On Arbor Day, Friday, April 29, tree people will plant three burr oaks and possibly some native chokecherry or plum to shade McGill Hall, said Benjamin Carson, grounds maintenance manager at UM. He said the plantings will add to UM's collection of some 2,250 to 2,300 trees.