During this time of year, visitors to the Asian Garden are greeted by an excellent colour display from this tree, Sorbus yuana (sorry, no common name). It often helps that there’s been some rain and the foliage is wet, saturating the colours even more brilliantly.
Sorbus yuana was only described as a species twenty or so years ago, several years after it was first collected during the 1980 Sino-American Botanical Expedition to Yunnan, China. Likely its scientific discovery took so long due to its habitat and location: steep ravine slopes above 2000m (6500ft.) in a remote mountainous region of China (source: Flora of China entry for Sorbus yuana).
A follow-up on the 1980 expedition was shared by Michael S. Dosmann and Peter Del Tredici in a 2005 report in Hortscience, “The Sino-American Botanical Expedition of 1980: A Retrospective Analysis of Success”. The authors state that of the 621 germplasm collections made, 258 accessions still survive in cultivation in one of eighteen botanical institutions. Of those, however, 115 are represented by only a single specimen at a single location (i.e., there’s no redundancy). In the case of Sorbus yuana, however, it is one of the 143 collections that can be found at multiple institutions: Arnold Arboretum, Holden Arboretum, UBC Botanical Garden and Royal Botanic Gardens Kew.