Few small ornamental trees offer so many attractive qualities in the landscape as the paperbark maple (Acer griseum). With its bright green leaves, coppery peeling bark, and vibrant fall color, this tree is highlighted in gardens across the country, and is specifically recognized as a Great Plant Pick for our region. At the University of Washington Botanic Gardens, we have six individual trees in our collections – one at the Center for Urban Horticulture and five at the Washington Park Arboretum.

It may surprise readers to know that paperbark maple is endangered in its native habitat in China, and only five known wild introductions have given rise to the thousands of trees gracing our gardens and landscapes (four known introductions in the US and one in the UK). With so few “parent” trees, there is likely very little genetic diversity to be found in cultivated trees of this species. Such a genetic bottleneck can reduce the resilience of a species, negatively impacting its ability to adapt to stressful environmental factors such as insect pests or a changing climate.

The endangered status of the paperbark maple, along with the limited genetic lineage of trees found in cultivation, has led researchers Anthony S. Aiello, Director of Horticulture and Curator at the Morris Arboretum of the University of Pennsylvania, and Kris Bachtell, Andrew Hipp, and Murphy Westwood, all from the Morton Arboretum in Lisle, Illinois, to embark on a project “to determine whether the diversity of cultivated plants in the US and UK accurately reflects the genetic diversity of plants in the wild, or if further efforts are needed to conserve this species” (“Paperbark Maple – A New Look at an Old Favorite”). The researchers have traveled to collect samples from trees across the US and UK, as well as trees growing in this species’ native range in China.

As part of this research, Anthony Aiello visited us at the Washington Park Arboretum last month to collect leaf samples and take measurements of our five older trees, which were introduced into our collections from 1947 to 1988. While it is thought that our collections also stem from the previously known introductions,  the samples collected will help provide a more complete picture of the genetic diversity that can be found in older cultivated plants.

This research is ongoing and we hope to learn more about the diversity found and what can be done to help conserve this beloved species.

Read more in these articles published by the researchers:

Aiello, A., and Backtell, K. “Paperbark Maple – A New Look at an Old Favorite.” Maple Society Newsletter. Winter 2015. Vol. 25/4.

Aiello, A. “Paperbark Maple – A New Look at an Old Favorite, Part 2.” Maple Society Newsletter. Summer 2016. Vol. 26/2.

Photo gallery of pictures from Anthony Aiello’s visit:

Copies of accession records for Acer griseum in the UW Botanic Gardens plant collection at the Washington Park Arboretum: