Anthony Aiello Gayle E. Mahoney Director of Horticulture and Curator

As described in the Winter 2015 Seasons, the Arboretum’s research and plant exploration program is a significant component of our mission.  As part of this program, for the past several years I have been involved in a conservation project involving paperbark maple (Acer griseum). Despite being a well-known and beloved garden plant, paperbark maple is endangered in its native habitat in central China.  There have been a limited number of introductions into Western cultivation, and as a result of this genetic bottleneck, there is probably little diversity among the plants within the United States or Europe.  The aim of this project is to determine whether or not the genetic diversity of cultivated plants accurately reflects that of plants in the wild, or whether further efforts are needed to help conserve this species. 

As explained previously, this project has sampled cultivated plants of known wild origin in the U.S. and U.K.  In September of 2015, we completed the next step of the project, which was to sample wild populations of Acer griseum across its native range in central China.  For this I visited wild populations in several provinces in China with Kris Bachtell (Morton Arboretum, Lisle, IL) and Michael Dosmann (Arnold Arboretum, Jamaica Plain, MA), where we worked with a long-standing colleague, Kang Wang of the Beijing Botanic Garden. 

With support received from The Maple Society and the Chanticleer Foundation, we travelled within an approximately 500 mile radius is Xi’an, the ancient capital of China and current capital of Shaanxi Province, a fascinating city whose history was shaped as a terminus of the Silk Road.  On our travels we visited paperbark maple populations stretching east to west from Shanxi, Henan, and Shaanxi to Gansu provinces, and south into Sichuan and Chongqing. 

The trip was especially informative because we were exposed to a wide range of conditions and habitats across the range of Acer griseum.  In total we came away with 66 samples of paperbark maple, from nine locations in five provinces.  Visiting the isolated populations, often a day’s drive apart, provided a graphic understanding of what it means for a species to be endangered.  In some of the sites we encountered trees scattered across a wide area, while in other sites there was a density of trees within a very restricted area.  In most situations we encountered very few young seedlings, indicating a reason for the species’ decline.  We also observed that there was great uniformity in the leaf shape, bark, and habit of trees, something that is certainly true among cultivated plants. 

Additionally, Chinese colleagues collected for us in Hunan Province, the southernmost populations of Acer griseum in China.  This coming summer we hope to obtain samples from Gansu province, an area we visited but could not find any trees.  At the Morton Arboretum the genetic diversity of all of these wild-collected leaf samples is being compared to those in cultivation.  If there is not sufficient representation of wild material in cultivation, then we will collaborate with our Chinese colleagues to expand ex-situ conservation efforts. 

With continued threats to plants around the world, this project has highlighted the importance of well-documented living collections in providing a basis for plant conservation efforts.  By providing an understanding of the number of botanic garden collections sufficient to help conserve this species, this project will serve as a model and benefit anyone interested in maple conservation.