Sorbus americana

American Mountain Ash

Sorbus americana, Mountain Ash

American Mountain Ash, BWCAW
Photo © by Earl J.S. Rook

Flora, fauna, earth, and sky...
The natural history of the northwoods


Name:

  • Sorbus, from the Latin name for Sorbus domestica, the common European Mountain Ash or "Service Tree"
  • americana, from the Latin, "of America"
  • Common Name from its North American distribution and the similarity of its compound leaves to those of the true Ash (Fraxinus spp).
  • Other common names include Dogberry, Small Fruited Mountain Ash, Roundwood, Missey-mossey, cormier (Qué)

Taxonomy:

  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Magnoliopsida, the Dicotyledons
      • Subclass Rosidae, the Roses
        • Order Rosales, the Roses
          • Family Rosaceae, the Roses; with Amelanchier (Juneberries), Aronia (Chokeberries), Crataegus (Hawthorns), Malus (Apples), Physocarpus (Ninebark), Potentilla (Cinquefoils), Prunus (Cherries & Plums), Rubus (Blackberries, Dewberries, and Raspberries), and Spiraea (Spirea)
            • Genus Sorbus, the Mountain Ash
  • Taxonomic Serial Number: 25319
  • Also known as Pyrus americana, Pyrus microcarpa
  • Hybridizes naturally with Black Chokeberry (Pyrus melanocarpa)

Description:

  • Leaves alternate, compound, 13"-17" long, tapered, finely toothed leaflets. The leaflets are 2-4 inches long, 5/8-1 inch wide, and without hairs.
  • Stem
    • Trunk short, slender
    • Branches spreading
    • Bark thin and smooth.
    • Bud Scales hairless and sticky.
    • Wood pale brown, soft, and weak.
  • Roots fibrous
  • Flowers small, creamy-white,and borne in cymes.
  • Fruit bright red, berry-like, about " in diameter, remaining on the tree late into the winter.
  • Seed
  • A native, deciduous shrub or small tree with a short trunk, slender, spreading branches, and a narrow, open round-topped crown; in closed canopies a longer trunk, with the lower portions branch-free.
  • Height 10'-30' with an average diameter of 4"-10"
  • Tends to be slow growing and short-lived in the wild.

Identification:

  • Identifiable as a Mountain Ash by the toothed compound leaves.
  • Distinguished from the only other North Woods trees with compound leaves, the true Ash, by the toothed leaf edges. Green Ash (Fraxinus pennsylvanica) and Black Ash (Fraxinus nigra) have smooth leaf edges.
  • Distinguished from the very similar Northern Mountain Ash (Sorbus decora) by:
    • Lateral leaflets averaging more than 3 times as long as wide, an hairy beneath.
    • Slightly smaller fruits which are bright red rather than orange/red.
  • Field Marks
    • Toothed, compound leaves
    • Bright red berries in fall

Distribution:

  • NE North America from Newfoundland and Nova Scotia south to New Jersey and Pennsylvania and in the mountains to South Carolina and Georgia, west to Minnesota and eastern North and South Dakota.

Habitat:

  • Prefers moist habitats from borders of swamps to rocky hillsides.
  • Common in openings or in woods, scattered on uplands along edges of woods, roadsides, and under semi-open stands. Grows in a stunted form on dryer soils.
  • Shade intolerant
  • More abundant in early succession communities, but present at low densities in old growth spruce-fir communities.
  • A favored food for Gypsy Moth larvae during all larval stages. It may be subject to severe defoliation at high levels of infestation.

Fire:

  • Not well adapted to survive fire; it is small, has thin bark, and occurs largely in areas that do not burn at frequent intervals.
  • Sprouts from stump if top-killed by fire.

Associates:

  • Trees: Balsam Fir (Abies balsamea)
  • Shrubs: Moose Maple (Acer spicatum), Twinflower (Linnaea borealis), Honeysuckle (Lonicera canadensis), Red Raspberry (Rubus idaeus), Yew (Taxus canadensis)
  • Herbs: Wild Sarsaparilla (Aralia nudicaulis), Blue Bead Lily (Clintonia borealis), Wood Fern (Dryopteris disjuncta), Naked Miterwort (Mitella nuda)
  • Ground Covers: Northern Clubmoss (Lycopodium annotium)
  • Mammals: Preferred browse for moose and white-tailed deer. Moose will eat foliage, twigs, and bark. Fishers, martens, snowshoe hares, and ruffed grouse also browse Mountain Ash. Berries eaten by small mammals, including squirrels and rodents.
  • Birds: Berries eaten by numerous species including ruffed grouse, ptarmigan, sharp-tailed grouse, blue grouse, jays, American robin, other thrushes, and waxwings.

History:

  • Fruit and inner bark have been used for medicinal purposes.

Uses:

  • Wood light, soft, weak, and close grained. Heartwood pale brown; sapwood thick and lighter in color. Not commercially important.
  • Planted for windbreaks.
  • Berries edible for humans but too acidic to be eaten raw. Can be cooked with meats or made into jelly.
  • The fruit of both Mountain Ash species is used to make homemade wines.

Reproduction:

  • Sexually by seed
  • Seeds largely dispersed by birds. Distance of dispersal probably ranges from a few hundred feet to a few miles.
  • Seeds require 60 days or more of cold stratification at 33-41 degrees Fahrenheit.
  • Highest rate of reproduction occurs in birch/fir/spruce communities.
  • Flowers May-July; fruit ripens in August. The berries remain on the tree and are available to birds all winter.
  • Asexual reproduction: will sprout from the stump when top-killed.

Propagation:

  • Seeds can be sown unstratified in early fall or winter. Sowing in July or August for germination the following spring also satisfactory, since a warm treatment prior to chilling is beneficial.
  • Seedlings quite hardy and not readily susceptible to insects or disease.

Cultivation:

  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Often grown as ornamental for the striking yellow to red autumn colors and red fruits, which remain on the tree well into the winter.
  • Prefers a moist, fertile soil; not successful where there is insufficient moisture. Not well adapted to warmer habitats.
  • Soil requirements for cultivation include a pH of 4.7 to 6.0, a minimum of 1.7% organic matter and 7% silt and clay particles with ground water at 1.5'-2.5'; 15% silt and clay particles with ground water deeper than 2.5'.
  • Many losses to fireblight in recent years; red fruits; fall color

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Last updated on 4 March, 2006