Rollinger Tree Project partners

The Rollinger Tree Collection 50-Year Survey Project is a collaboration between Denver Botanic Gardens, Denver’s Office of the City Forester, Colorado State University Extension, Colorado State Forest Service, the Colorado Tree Coalition and other local participants to revisit a survey of major trees done in 1968 by Alan Rollinger in order to gain insight into the history, health, and future of Denver’s urban trees.


In 1968, Al Rollinger was a young landscape designer, recently graduated from CSU. Curious about the kinds of trees growing in Denver, he decided to do a survey of the more unusual trees, ones other than the very commonly planted species like American elm, silver maple, honeylocust and green ash. Therefore, he undertook the huge effort of doing a street-by-street survey, noting the species, location, diameter, and height of over 1,100 trees of 46 species. In 1969, Al documented the results of his survey in a written report.

The Project

Now, almost 50 years later, we have realized how valuable the data collected in this survey could be to analyze the health, mortality, and growth patterns of these various species in the Denver area.

We are currently in the process of finding, measuring and taking photographs of the trees surveyed in 1968 to determine which are still alive and to determine growth patterns. These data will be analyzed and stored in a database held by the Denver Office of the City Forester, and will be reported in a book publication to include the results of the data analysis, before and after pictures, stories of some of the most interesting or unique trees and implications for the future of trees in Denver. We expect that this study will provide a wealth of information that can be used to assess which tree species are best suited to Denver’s climate, and act as a guide to future tree planting.

Submit Consent Form Online

If we have notified you that one of the Rollinger Trees is located on your property and you would like to fill out the consent form online, click on the orange button at the top of this page.

Please contact Ann Frazier at for more information.