This hybrid mountain ash was first discovered in Finland, so can be regarded as a native. However, in addition to south-west Finland, it also grows naturally on Swedish islands and in Norway. Pietari Kalm called the tree S. fennica but nowadays it is called S. hybrida, the name given to it earlier by Linné, which acknowledged its hybrid status. Linné believed its parents to have been the rowan (S.aucuparia) and the Swedish whitebeam (S. intermedia), but it has later been shown that this second parent was the whitebeam S. aria. Its ancestry thus includes both native and exotic genes, so the tree has been adopted as the emblem of the Finnish Dendrological Society.
Hybrid mountain ash is a healthy tree well suited to streets and parks, and can even be used for hedging. The leaves on flowering shoots have one or two pairs of separate leaflets at their base, and the undersides are covered in grey-green felt. As with other mountain ash species, the flowers are creamy white and scented. The red, round, sweet-tasting berries ripen in September.
Slight variations between individual trees are an indication that crossings between the parent species have happened several times in different areas. Plants raised from seed are usually clones of the mother tree, but sometimes crossings with other mountain ash species do occur.