Mountain Ash

European Mt. Ash (Sorbus aucuparia)

            This is surely one of my favorite ornamental trees for the front range which can be used up to 8000’.It is an upright oval tree spreading with age 25’-30’ tall aned 15’-25’ wide. If cared for, it will be attractive throughout the season. The bark is a shiny, orangy-brown. The serrated, compound leaves are dark green and in the fall turn yellow and reddish-gold. The clusters of flowers are white, blooming in spring with a peculiar fragrance that some people appreciate more when they’re gone. Clusters of red-orange berry-like fruit follow which color the tree through the fall, accenting the orangy leaf colors. These fruits are greatly loved by the birds and are in fact edible for people. They are known as Rowan berries and are used in Europe in making a brandy. In ancient times the Rowan tree, also know as the Quickbeam, was greatly revered by the Druids and used against lightning and witches’charms. The berries were considered extremely valuable having the “sustaining value of nine meals”, healing the wounded and giving a man the strength of ten men. I had to try this, of course, and found I couldn’t eat even 10 berries. Later I learned they need to “blet” or shelf-ripened. The birds do spread these around, and Mt. Ash seedlings are not uncommon.

            Like most members of the Rose Family, Mt. Ash likes well-drained soil, although they grow well enough in Boulder County’s clay soils as long as they aren’t over-watered. Whereas they do appreciate some extra water during blooming and fruit-production, they are quite drought-tolerant once established. Soggy conditions, severe pruning, over-fertilization or other stresses can result in fireblight, which can be serious if ignored, however the majority of Mt. Ashes do not have a fireblight problem. If the branches are tending to grow too tightly vertical it is good to thin them and to prune to a shoot leading away from the center. Any sucker growth around the trunk should also be removed before it gets large.

            Some other varieties that can be grown here are:

Sorbus aucuparia ‘Rossica’, the Russian Mt. Ash, slightly smaller and resistant to fireblight

Sorbus aucuparia ‘Cardinal Royal’, to 15’ with brilliant red berries

Sorbus alnifolia, beech-like leaves and scarlet berries

Sorbus hybrida, Oakleaf Mt. Ash with lobed leaves and deep red fruit.