American mountain ash: A rosaceae by any other name

Illustration by Adelaide Tyrol
In this illustration by Adelaide Tyrol, a bird eats the berries from an American mountain ash.


There’s a giant living in northern Coös County, N.H.

It’s a 61-foot tall tree, the country’s largest known American mountain ash. At last measurement, it stood at a height of 61 feet and had a circumference of 70 inches. That’s outstanding for a tree that’s described by most sources, including my old dendrology textbook, as “a small tree or shrub.”

This tree is a champion – but the species as a whole has a lot going for it. I love the mountain ash for the beauty of its white flower clusters and red berries. More importantly, though, it fills an important spot on the menu for birds and mammals, especially in winter.

Despite its common name, the American mountain ash is not an ash, but a member of the rose family, along with black cherry, hawthorn and shadbush.

The confusion is due to its leaves, which bear a resemblance to those of the white ash. The two are easy to differentiate, however. The compound, toothed leaves of the mountain ash are alternate, not opposite, meaning the leaves or buds do not appear directly across from one another on the twig.

Mountain ash grows throughout the northeastern United States and eastern Canada, extending south to the mountains of Georgia. In New England, I see it growing on high ridges and steep, rocky hillsides. They prefer moist, slightly acidic soil and grow best in full sun. They thrive in open areas such as hilltops, roadsides, and the edges of swamps, and quickly regenerate a cut-over area or storm blowdown.

Starting in late May, the mountain ash stands out in the forest because of its creamy-white flowers. In the fall, the foliage turns yellow and the flowers are replaced by small red berries. These berries hang on during the winter, which is why it’s an important food source for birds such as robins, waxwings and ruffed grouse.

Dave Govatski, a forester and birder who lives in Jefferson, N.H., samples locations in the White Mountains and Vermont’s Northeast Kingdom as a volunteer on a winter finch survey. By reporting the berry and cone crop in August, he contributes data to a winter finch forecast that is released every September.

“Birds just love those berries,” he said. “We don’t get a good berry crop every year, but when we do, we’ll see pine grosbeaks, Bohemian waxwings, and American robins feeding on them all winter. Some winters I’ve seen robins singing away like it’s summer at 4,000 feet on Mount Clinton. This isn’t a good winter for a bumper berry crop, but maybe next winter will be better.”

Mountain ash is also preferred by moose, which snack on the foliage, twigs, bark and buds. It also provides forage for white-tailed deer, marten, snowshoe hare, squirrels and other rodents.

Thanks to its value to wildlife, mountain ash sometimes gains an advantage, according to Brendan Prusik, who measured Coös County’s champion. Before joining the UNH Cooperative Extension Service, he worked for a paper company. It was not uncommon to promote mountain ash, he notes.

“When we came upon one, we’d open that area up, retaining the tree at the cost of spruce and fir, to maintain the diversity of the forest and because of its wildlife value,” Prusik said.

Besides its important role in the forest ecosystem, the mountain ash holds a prominent place in folklore and mythology. My interest in the mountain ash was sparked by “The Golden Bough,” a classic study of folklore, religion, and magic by the Scottish social historian Sir James Frazer. The book devotes an entire chapter to trees.

Greek and Norse mythology contain references to the mysterious power of the American mountain ash’s European relative, known as the rowan tree. In the British Isles, the rowan tree warded off witchcraft and enchantment. It’s possible that the belief in its power is due to the pentagram marking on the bottom of the berry.

Some of these superstitions crossed the ocean to the New World. Not surprising, one of its common names is witchwood. But whether or not you can ward off hexes with a cross of mountain ash wood, there is much to enjoy and appreciate about Sorbus americana.

Laurie D. Morrissey is a writer in Hopkinton, N.H. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of the New Hampshire Charitable Foundation.

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