The confounding Mountain Ashes

Mountain ashes are not true Ash trees and are not subject to ash borer.

First, mountain ash trees are not really ash trees. True ash trees are in the olive family while mountain ash trees are in the rose family. There are five types of mountain ash listed on the Arboretum guide and I’m discussing them all here, partly because there isn’t much to say about specific cultivars. 

We first located the Oakleaf Mountain Ash (Sorbus x  thurgingiaca Quercifolia). This might be the most local of local trees as it was cultivated in Cheyenne! This particular tree seems both similar and different from those discussed below. It has similar slits in its bark, yet these are more vertical, not horizontal. There is a slight sheen to the bark and it appears thinner than the bark of other trees. The leaves are not similar to the other mountain ashes, but resemble oak leaves.

Oak Leaf Mountain Ash
Oakleaf mountain ash leaves in fall

A76 is located near the pottery studio (corner of S. Bryan and Oak Street.) 

The other four Sorbus trees are at the other end of Oak Street and have leaves that resemble “real” ash trees.

The American Mountain Ash (Sorbus americana) is native to the Eastern part of the continent, but has been introduced to most of the rest of the continental US, including Colorado. B106 is across the street from 1334 W. Oak Street. The bark of this small tree is reddish with a metallic sheen. There are horizontal lines that resemble healed cuts across the bark and visible reddish berries (pomes) in the upper branches. Native Americans such as the Algonquin and Ojibwa ate the berries from this and related species. 

American Mountain Ash bark
American Mountain Ash bark. Notice the metallic sheen.

The European Mountain Ash  (Sorbus aucuparia) has been introduced to much of the northern part of North America. In England these are referred to as Rowans and the berries are made into jams and sometimes wine. There seems to be controversy about how tasty these are as many say they are bitter and must be cooked or undergo numerous freezes on the tree before they are edible. According to the source above, the berries are a good source of vitamins A, C and niacin. The Rowan also has a place in many European mythologies and is considered by some to have magical powers. Its wood has been made into walking sticks and spinning wheels.

It appears there are two cultivars of the European Mountain ash in City Park. B109 Cardinal Royal Mountain Ash (Sorbus aucuparia Cardinal Royal) is near the Kentucky Coffee Tree, across from 1316 West Oak. The bark of this tree is very grey-green, more reddish at the base.

Cardinal Mountain Ash bark

The other cultivar is the Russian Mountain Ash (Sorbus aucuparia Rossica.) B102 is across from the intersection of McKinley and Oak. As is noted in the write-up referenced above, this tree, with its yellow-green tinged skin, seems to have more noticeable berries. 

Russian Mountain Ash trunk
This straggly tree IS NOT a mountain ash at all but a linden!

The last mountain ash tree in City Park is the Showy Mountain Ash (Sorbus decor), which once again is native in the northeastern part of the continent where it is also known as the Northern Mountain Ash. I made many trips across the street to locate this tree. What I finally settled on as B103 wasn’t particularly showy and was very difficult to find. Possibly this is because it is not tagged, and it is also not very large, which might have an effect on some of its notable properties, such as large, showy berries. See for yourself. Would you have known this was a showy tree?

UPDATE 3/23/18: Today I spoke with City Forestry Specialist, Molly Roche. No wonder I had such a difficult time finding the Showy Mountain Ash. It ISN’T THERE. After it was discovered not thriving, it was removed and replaced with a Legend Linden. THAT is what the not particularly showy tree actually is!