Sorbus americana

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Sorbus americana
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]
Marshall

The tree species Sorbus americana (syn. Pyrus americana) is commonly known as the American Mountain-ash.[3] 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 40 feet (12 m) in height.[1] The American Mountain-ash attains its largest specimens on the northern shores of Lake Huron and Lake Superior.[4]

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. Sp. gr., 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: (see Leaf shape for explanation of terms) Alternate, compound, odd-pinnate, six to ten inches long, with slender, grooved, dark green or red petiole. Leaflets thirteen to seventeen, 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.[4]
Distribution map of native Sorbus americana range.

Distribution

Native to eastern North America;

  • Eastern Canada — New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, Quebec.[5]
  • Northeastern United States — Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Vermont.
  • North-Central United States — Illinois [n. (Ogle Co.)], Michigan, Minnesota, Wisconsin. Listed as endangered by the State of Illinois.[6]
  • Southeastern United States — Appalachian Mountains, Georgia, Maryland, North Carolina, Tennessee, Virginia, West Virginia.

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.[7]

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.[8]

See also

  • Rhus glabra (Smooth Sumac) - similar leaf pattern arrangement.

References

  1. ↑ 1.0 1.1 1.2 McAllister, H.A. 2005. The genus Sorbus: Mountain Ash and other Rowans . Kew Publishing.
  2. ↑ http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=25319&print_version=PRT&source=to_print ITIS Report Sorbus americana
  3. ↑ http://plants.usda.gov/java/charProfile?symbol=SOAM3 USDA Natural Resources Conservation Service
  4. ↑ 4.0 4.1 Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scriber's Sons. pp. 136–140. 
  5. ↑ http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?34994#uses USDA Germplasm Resources Information Network (GRIN)
  6. ↑ http://plants.usda.gov/java/threat?statelist=states&stateSelect=17 USDA Natural Resources Conservation Services Threatened and Endangered Species (Illinois)
  7. ↑ http://www.fs.fed.us/database/feis/plants/tree/sorame/all.html fs.fed.us/database
  8. ↑ Urban Forest Nursery: Tree Profile for the Red Cascade Mountain Ash . accessed 1.31.2013

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