I contributed the scan for today’s Botany Photo of the Day, while Eric La Fountaine is responsible for the writing (thanks Eric). Eric writes:
The identity of the tree providing the leaf for today’s Botany Photo of the Day image had been a mystery at the garden since the tree was planted in 1988. The plant came to us as a scion from a Sorbus collected in 1976 by Tor Nitzelius on the South Korean island, Ulleungdo. With its large leaves and long internodes, the tree has a striking, almost tropical, appearance. It was thought to most closely resemble Sorbus commixta–a species from Japan, Korea, Sakhalin and the Kurile Islands of Russia–but the description of Sorbus commixta does not quite fit the specimen.
After 24 years, we still had not put a precise name to the tree, so I sent an email to the Gothenburg Botanical Garden in Sweden, where our plant was sourced. Mats Havström, Senior Scientific Curator, replied that they had also determined it to be closest to Sorbus commixta. At Gothenburg, the taxon is referred to as either “Sorbus ‘Ullung-do'” or “Sorbus commixta subsp. novum?” (meaning–is it a new subspecies?). The leaves of our plant at UBCBG are 30+ cm long with leaflets to 100 mm–somewhat larger than the maximum size normally attributed to the species. The fruit also exceeds the normal size and is soft, pear- or teardrop-shaped and held loosely as compared to the usually hard, round fruit of Sorbus commixta, borne in tighter clusters.
Mr. Havström also wrote, “The collections have also given rise to a horticultural selection made by the Swedish University of Agricultural in Alnarp, called Sorbus ‘Dodong’, which has received the Swedish Elite Plant award, “E-planta” and has become quite popular in Nordic gardens.” Sorbus ‘Dodong’ (note: linked page is a Google translation from Swedish) has become a popular landscape introduction in Sweden. The medium-sized tree has a narrow form and sports blazing autumn leaf colour. This tree is also being marketed under the trade name Olympic Flame.
The tree here at UBC Botanical Garden is at least 10 metres tall, but with a broad spread. The fruit are large, glossy red and teardrop- or pear-shaped. The autumn colour is also striking, but quite different than Sorbus ‘Dodong’. Here, the leaves turn bright yellow with red to brownish-red leaflet tips. Some leaves remain yellow and others turn mostly red as in today’s image. I have uploaded several less artistic images to the garden’s forums that show dimension and colour of the tree at UBCBG. Very little fruit had been seen on the tree in previous years and it was generally out of reach. In collecting, I noted that some fruit had small slices in the side and the seed had been eaten, perhaps by a jay. Seed was extracted from the fruit in the photos and is in cold stratification. Hopefully, germination will be successful in the spring. For the moment, we are calling the tree here at UBC Botanical Garden Sorbus commixta N100.