The natural habitat of the Korean mountain ash is typically among the volcanic lava of East Asia, indeed the Finnish common name is ”lava mountain ash”. It is one of the group of Sorbus species which have entire leaves and includes the whitebeams. Indeed, the shape and structure of the leaves resemble the beech (Fagus sylvatica) rather than what we usually expect in a mountain ash. The leaves open a fresh green in a characteristic zig-zag attitude and form attractive patterns along the branches. When fully developed, the foliage is a shiny dark green, changing in autumn to yellow, golden brown and shades of orange. The chestnut-coloured shiny branches are also attractive after leaf fall.
The species bears white inflorescences typical of the genus but the small oblong red-orange berries are noticeably different from the other mountain ashes. They aren’t first choice among birds so often remain on the tree long into winter. When the trunk is also beautiful, what more could a garden tree offer?
In full light, Korean mountain ash develops a narrow oval habit; in less favourable spots it becomes a multi-stemmed large shrub. The specimens growing at Mustila originate from different parts of its natural range so we will soon be able to compare their habit, characteristics and hardiness.