Unique Features: Mountain Ashes, also known as Rowans, are not susceptible to the Emerald Ash borer because they are not ashes, nor are they oaks (and you thought botanical names were confusing). The Oak Leaf Mountain Ash is a natural hybrid of the European and Scandinavian varieties. It is very cold hardy and soil tolerant. It grows moderately fast, into an upright oval shape. The leaflets of the normally pinnate leaves grow together, except at the base, to give the impression of an oak leaf. The dark green leaves are fuzzy white underneath, also a characteristic found on oak leaves. Clusters of mid spring white flowers mature into orange-red berries that persist into winter and are favored by the birds. The red-brown bark shows well against the winter snows.  Mountain Ashes are susceptible to fire blight and should be monitored for signs of infection.