Sorbus – What Tree Where

Swedish Whitebeam-Don’t Let the Tag Fool You!

What do I know about the Swedish Whitebeam tree? It belongs to the genus Sorbus which is in the rose family. This large family of over 3000 species includes apples, cherries, plums, pears, and mountain ashes, as well as the flowers known as roses. Mountain ash trees are members of the same genus (Sorbus) as white beams and therein may lie some of my confusion in finding this speciman. I kept returning to the area on the tree map where this species was said to be located, but the unmarked trees in the area seemed to be true ashes and elms. The one unusual tree had leaves that were completely wrong. I thought I knew the smaller deciduous tree was an Oakleaf mountain ash as I’d read the tag the year before.

P9280006_01 — The darker green Sorbus intermedia in forefront

As the name implies, the Swedish whitebeam is not native to North America. As it doesn’t appear on the USDA maps, it must not be considered significant in the United States, although Toronto mentions it on its parks pages. In Great Britain it is suggested as a street tree. One source suggests it can withstand harsh conditions, is hardy to zone 3, and grows on Shetland Island. It may also be a tree useful for birds and bees.

The wood of the whitebeam has been used for handles, wheels and cogs. According to a few sources, the berries have been used to make bread and jam or used similarly to raisins. They may also be distilled into spirits.

As mentioned above, some of the confusion in finding this tree may be related to some of its attributes. Whitebeam are related to mountain ash trees and rowans. Tree Names lists fifty species of whitebeam, but also mentions whitebeams and rowans naturally hybridize. Some authors hypothesize that Swedish whitebeam are a hybridization of mountain ash and two other species or are derived from the Finnish whitebeam. With all the mountain ash genes involved, it isn’t surprising the sign on the Swedish Whitebeam

P9280001_01 — Swedish whitebeam with correct latin name on label.

displays Oakleaf Mountain Ash as a common name along with the latin name of Sorbus intermedia, or that of the Swedish Whitebeam. Seems like it just continues the confounding nature of the Sorbus genus!

P9280003_01 — The leaves of the Swedish whitebeam looking very similar to that of the Oakleaf mountain ash.

And why the two trees are so easy to confuse:

The tree on the Fort Collins City Park Self-Guided Tree Tour was planted in 1994 with a 2″ diameter. Although they are supposed to have white flowers in Spring turning to red berries in fall, no berries were visible in late September. This tree may live to 134 years.

To locate tree D192 Swedish Whitebeam (Sorbus intermedia), go to the southwest corner of the intersection of Sheldon and City Park Drives. This section is lined on the north and east by elms and ash trees with conifers making up the other boundaries. In the center are two conifers, the Engelmann Spruce and a Baker’s Blue Spruce. Of the three deciduous trees, the Swedish whitebeam is the most southerly and smallest. It is also the only one with a visible tag.

How a Little Green Jewel Beetle May Change Major League Baseball Lovers Way of Life—The Real Ash Trees

Leaves of ash trees were used to ward off snakes,

The White Ash tree (Fraxinus americana)

P6300028 — Trunk of the White Ash with a 75 lb. Irish Water Spaniel sitting in front of it.

is another tree native to the eastern half of the continent. Unlike most other trees from the east, the USDA lists its native range as extending into Colorado. Flora of Colorado (Ackerman) says this species does not “persist outside of cultivation,” though. She also mentions it is very similar to the Green Ash (Fraxinus pennsylvanica,) which is native to Larimer County as well as most of the rest of the continent. Oddly, the Green Ash is also known as Red Ash. Unfortunately, both trees are on the critically endangered list.

The national champion white ash, nominated in 2012, is in New Jersey and has a total of 398 points, compared to the Colorado champion which only has 288.9 points. The second and third largest Colorado ash trees are in Fort Collins, both in City Park, but only the smaller of the two is tagged. You can locate the runner up tree by using the Notable Tree Tour map of Fort Collins. The National Champion Green Ash is in Virginia. It has a total score of 355, while the Colorado champion, located in Greeley, has a score of just over 315.

An interesting early use of the ash tree

P6300011 — White Ash tree-tied for 3rd largest in Colorado

was for people to stuff their shoes and pockets with leaves as these were said to ward off snakes. Ash trees in Viking legend involve the creation of man. Interestingly, this was also part of Algonquin Legends. In modern “legend” ash wood has figured in Harry Potter. More prosaic uses of ash lumber are in baseball bats, guitars, bows, hockey sticks and tool handles. Juicing the leaves

P6300038 — White Ash leaves hit by two hail storms

results in a topical treatment for mosquito bites. The tree provides food for birds and other small animals as well as shade, and is a valuable member of the ecosystem.

The emerald ash borer is a major threat to the species. This introduced pest was first detected in the US in 2002, but it is thought that the first invaders appeared in Michigan in the 1990s. A similar invasion affecting European ash trees has been noted in Russia. As of this year, 33 states and three Canadian providences have been confirmed to be infected. Millions of trees have already been lost. In the Denver area alone there are nearly 1.5 million ash trees and in certain parts of Colorado ash trees could account for 80% of the urban forest. There are over 3000 ash trees in the city of New York. A bulletin was issued in October, 2017 that emerald ash borers had been found in the boroughs of NY.

Although this pest could be devastating to the ash population, there are steps that can be taken to help protect trees. Some of these involve not assisting in the spread of this problem. You can inoculate your own trees when the threat has reached your area. For a tree to be a candidate for injection or spraying, it needs to be healthy. Unfortunately, emerald ash borer is not the only threat to ash trees. The white ash is sensitive to ozone and other gas levels and also prone to ash decline.

The Coalition for Urban Ash Tree Conservation has a position paper on reasons and methods to work with this growing problem, as does the Society for Municipal Arborists.The Emerald Ashborer Information Network includes various links to assist individuals, neighborhoods and cities in working with this virulent problem. Nearly all states seem to have a set of guidelines to follow.

Why should this little green pest be of interest to you? Are you a fan of major league baseball? Did you know the bats used in league play, most of which are made by Louisville Slugger have used wood from an area now devastated by the emerald ash borer? If you are a woodworker, the loss of this abundant and inexpensive wood could be a factor in future projects.

An interesting study which should be of concern to all of us recently concluded human health can be linked to the loss of trees, specifically the ash trees. The presence of emerald ash borer and subsequent decline in the ash tree population was associated with an increase of over 20,000 deaths related to respiratory or cardiovascular causes.

P6300020 — Winged fruit of the green ash tree.

At least some believe the increase in deaths is related to the ability of trees and forests to help humans deal with stress.

Another point to remember is that genus Fraxinus are the trees being devastated by the borer. Mountain Ash (Sorbus) trees are not affected.

Finding some of the ash trees in Fort Collins City Park.

Both a large green ash tress and a large white ash are located behind the tennis courts. You could park near the trolley terminal and walk West to find A78 White Ash (Fraxinus americana) located behind the pickle ball courts.

P6300023 — Green Ash tree on the edge of the playground

Almost due South is the Green Ash (Fraxinus pennsylvanica) E80. There is a smaller maple tree between the two.

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.

PA270010 — 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. 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.

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.

PB190051 — 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!