Some scientists say the trees' longevity may result more from luck than genetics. They hope eventually to produce enough clones to populate forests with hardy, disease-resistant specimens. American Forests of Washington, D.C., designates national champions based on height, trunk girth, crown spread. Present list includes 867 champions representing 826 species. Its trunk girth exceeds 83 feet.
List varies from year to year as champions die or are discovered.
Nurseries use different cloning methods, including grafting cuttings onto roots of other trees and using hormones to make cuttings grow roots. There are 867 national champions representing 826 species, program coordinator Katie Byrne said. Some species have co-champions because of similar scores. Florida leads the nation with 172 national champions. Michigan ranks sixth with 51, including the American elm in Buckley, about 18 miles south of Traverse City.