5 p.m., May 13 & 14 Two tours of CU's unique historic campus "forest" will be led by veteran and Senior Grounds Specialist Alan Nelson. Along with the spring blooms, he will share the unique characteristics and special historical significance of these trees. Since the first plains cottonwoods were planted near Old Main, CU’s tree population has grown to nearly 5,000 and more than 100 species, many imported from across the United States, Europe and Asia. The tour will depart from the Museum's south entrance.