Species of Sorbus have made a frequent appearance on Botany Photo of the Day, and it is no wonder, as UBC Botanical Garden hosts many beautiful specimens of this genus. Walking around the garden last week, it was impossible not to notice the white, pink, orange, and red fruits of the many Sorbus spp. in the collection. Daniel and other BPotD writers have posted about Sorbus pallescens, Sorbus commixta, Sorbus yuana, Sorbus scopulina, and Sorbus hupehensis. Today I have chosen to write about a Sorbus that I have seen frequently on hikes around southern British Columbia, Sorbus sitchensis, or Sitka mountain ash.
Sorbus sitchensis is a large, multi-stemmed shrub (or small tree) that can be found along the northwestern coast of North America. It is quite similar in appearance to Sorbus scopulina, but here is one way to tell the two species apart: Sorbus scopulina has leaflets that are lanceolate and strongly serrated, while Sitka mountain ash leaflets are elliptical and only serrated at the ends. The small fruits (pomes) of Sitka mountain ash are red to orange, and are an important source of autumn and winter food for many animals. Previous Sorbus postings and discussions on Botany Photo of the Day commented on the love that American robins (Turdus migratorius) and other birds have for this fruit (and its intoxicating effects when fermented). Another animal species that favours Sitka mountain ash fruit is the American black bear (Ursus americanus), which takes advantage of the autumn berries to put on a few last-minute kilograms before winter hibernation.
Sitka mountain ash is a factor in the ongoing conflict between black bears and humans in Whistler, British Columbia, Canada. Whistler is a globally-known ski resort that has expanded rapidly since it hosted the Winter Olympics in 2010. Because black bears are attracted to Sorbus sitchensis fruits, homeowners in Whistler have been asked to remove the trees from their properties. Also, new landscaping installations in Whistler can no longer include Sorbus species that are palatable to bears. In an effort to draw bears away from residential areas, the Get Bear Smart Society is planting Sitka mountain ash and Vaccinum species in remote parts of Whistler mountain, where the black bears will be able to feed undisturbed. This story is a good reminder that our choice of plants in landscaping decisions has a major effect on all wildlife, even those whose presence is less noticeable than the black bear’s.