Sorbus americana

American mountain-ash
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Rosaceae
Genus: Sorbus
Section: Commixtae[1]
Species: S. americana
Binomial name
Sorbus americana[2]
Synonyms[3]
  • Aucuparia americana (Marshall) Nieuwl.
  • Pyrus americana (Marshall) DC.
  • Pyrus americana (Marshall) Spreng.

The tree species Sorbus americana is commonly known as the American mountain-ash.[4] It is a deciduous perennial tree, native to eastern North America.[1]

The American mountain-ash and related species (most often the European mountain-ash, Sorbus aucuparia) are also referred to as rowan trees.

Description

Sorbus americana is a relatively small tree, reaching 12 metres (40 ft) in height.[1] The American mountain-ash attains its largest specimens on the northern shores of Lake Huron and Lake Superior.[5]

It resembles the European mountain-ash, Sorbus aucuparia.

  • Bark: Light gray, smooth, surface scaly. Branchlets downy at first, later become smooth, brown tinged with red, lenticular, finally they become darker and the papery outer layer becomes easily separable.
  • Wood: Pale brown; light, soft, close-grained but weak. Specific gravity, 0.5451; weight of cu. ft., 33.97 lbs.
  • Winter buds: Dark red, acute, one-fourth to three-quarters of an inch long. Inner scales are very tomentose and enlarge with the growing shoot.
  • Leaves: Alternate, compound, odd-pinnate, 6 to 10 inches (15 to 25 cm) long, with slender, grooved, dark green or red petiole. Leaflets 13 to 17, lanceolate or long oval, two to three inches long, one-half to two-thirds broad, unequally wedge-shaped or rounded at base, serrate, acuminate, sessile, the terminal one sometimes borne on a stalk half an inch long, feather-veined, midrib prominent beneath, grooved above. They come out of the bud downy, conduplicate; when full grown are smooth, dark yellow green above and paler beneath. In autumn they turn a clear yellow. Stipules leaf-like, caducous.
  • Flowers: May, June, after the leaves are full grown. Perfect, white, one-eighth of an inch across, borne in flat compound cymes three or four inches across. Bracts and bractlets acute, minute, caducous.
  • Calyx: Urn-shaped, hairy, five-lobed; lobes, short, acute, imbricate in bud.
  • Corolla: Petals five, creamy white, orbicular, contracted into short claws, inserted on calyx, imbricate in bud.
  • Stamens: Twenty to thirty, inserted on calyx tube; filaments thread-like; anthers introrse, two-celled; cells opening longitudinally.
  • Pistil: Two to three carpels inserted in the bottom of the calyx tube and united into an inferior ovary. Styles two to three; stigmas capitate; ovules two in each cell.
  • Fruit: Berry-like pome, globular, one-quarter of an inch across, bright red, borne in cymous clusters. Ripens in October and remains on the tree all winter. Flesh thin and sour, charged with malic acid; seeds light brown, oblong, compressed; cotyledons fleshy.[5]
Distribution map of native Sorbus americana range.

Distribution

Native to eastern North America;

Biota

The berries of American mountain-ash are eaten by numerous species of birds and small mammals, including ruffed grouse, ptarmigans, sharp-tailed grouse, blue grouse, American robins, other thrushes, waxwings, jays, squirrels, and rodents.

American mountain-ash is a preferred browse for moose and white-tailed deer. Moose will eat foliage, twigs, and bark. Up to 80 percent of American mountain-ash stems were browsed by moose in control plots adjacent to exclosures on Isle Royale. Fishers, martens, snowshoe hares, and ruffed grouse also browse American mountain-ash.[8]

Cultivation

Sorbus americana is cultivated as an ornamental tree, for use in gardens and parks. It prefers a rich moist soil and the borders of swamps, but will flourish on rocky hillsides.

A cultivar is the red cascade mountain-ash, or Sorbus americana 'Dwarfcrown'. It is planted in gardens, and as a street tree.[9]

References

  1. 1 2 3 McAllister, H.A. (2005). The genus Sorbus: Mountain Ash and other Rowans. Kew Publishing.
  2. ↑ ITIS Report Sorbus americana
  3. ↑ "Sorbus americana". Tropicos. Missouri Botanical Garden.
  4. ↑ "Conservation Plant Characteristics for ScientificName (CommonName) - USDA PLANTS". plants.usda.gov.
  5. 1 2 Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scriber's Sons. pp. 136–140.
  6. ↑ "Sorbus americana". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA).
  7. ↑ "Threatened Search Results - USDA PLANTS". plants.usda.gov.
  8. ↑ "Fire Effects Information System".
  9. ↑ "Urban Forest Nursery: Tree Profile for the Red Cascade Mountain Ash". www.urbanforestnursery.com. Retrieved January 31, 2013.
  • "Sorbus americana". Natural Resources Conservation Service PLANTS Database. USDA.
  • Sorbus americana – picture of young tree, and complete summary data
  • Interactive Distribution Map for Sorbus americana
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