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Native Plant Trust: Go Botany Discover thousands of New England plants

Sorbus americana — American mountain-ash

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Facts

This small tree of mid-elevations and cool climates is called American mountain-ash because its compoud, toothed leaves resemble those of ash (Fraxinus) species. However, unlike ash, American mountain-ash leaves are alternate, not opposite. Although people find the berries somewhat bitter when raw and can be mildly toxic, many species of birds, including waxwings, robins, jays, and grouse find them delicious. Mountain ash leaves, twigs, and bark are a favorite food of moose and deer.

Habitat

Alpine or subalpine zones, forests, mountain summits and plateaus, ridges or ledges, swamps

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
  • terrestrial
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Growth form
the plant is a tree
Leaf type
the leaf blade is compound (i.e., made up of two or more discrete leaflets
Leaves per node
there is one leaf per node along the stem
Leaf blade edges
the edge of the leaf blade has teeth
Leaf duration
the leaves drop off in winter (or they wither but persist on the plant)
armature on plant
the plant does not have spines, prickles, or thorns
Leaf blade length
100–220 mm
Leaf blade width
60–120 mm
Leaf stalk
the leaves have leaf stalks
Fruit type (general)
the fruit is fleshy
Bark texture
the bark of an adult plant is thin and smooth
Twig winter color
  • brown
  • gray
  • red
Bud scale number
there are three or more scales on the winter bud, and they overlap like shingles, with one edge covered and the other edge exposed
Show all characteristics

  • Buds or leaf scars

    Bud scale number
    there are three or more scales on the winter bud, and they overlap like shingles, with one edge covered and the other edge exposed
    Bud scar shape (Fraxinus)
    NA
    Collateral buds
    there are no collateral buds on the sides of the branches
    Leaf scar arrangement
    there is one leaf scar per node on the stem or twig
    Superposed buds
    there are no superposed buds on the branch
    Terminal bud
    the branch has a terminal bud on it
    Winter bud distribution
    the winter buds are distributed fairly evenly along the twig
    Winter bud scale hairs
    • the winter bud scales are hairy
    • the winter bud scales have no hairs on them
    Winter bud scales
    the winter bud is perulate (partially or completely covered with one or more scales)
    Winter bud shape
    the winter buds are ovoid (egg-shaped)
    Winter bud stalks
    the winter buds have no stalks

  • Flowers

    Carpels fused
    the carpels are fused to one another
    Enlarged sterile flowers
    there are no enlarged sterile flowers on the plant
    Flower petal color
    white
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Hairs on ovary (Amelanchier)
    NA
    Hypanthium present
    the flower has a hypanthium
    Inflorescence hairs
    there are no hairs on the inflorescence
    Inflorescence type
    • the inflorescence is a corymb (with long lower branches and shorter upper branches, giving it a more or less flat-topped look)
    • the inflorescence is a dichasial cyme (an axis with a terminal flower, below it a pair of branches, each with a terminal flower, these branches may in turn each have a pair of branches and so on)
    Number of pistils
    1
    Ovary position
    • the ovary is above the point of petal and/or sepal attachment
    • the ovary is below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal fusion
    the perianth parts are separate
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal cilia (Ilex)
    NA
    Sepal tip glands
    there are no glands at the tips of the sepal lobes
    Stamen number
    13 or more
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are not fused to one another

  • Fruits or seeds

    Berry color
    • orange
    • red
    Fruit tissue origin
    the hypanthium of the flower becomes part of the fruit
    Fruit type (general)
    the fruit is fleshy
    Fruit type (specific)
    the fruit is a berry (fleshy, with the wall enclosing one or more sections, with two or more seeds)
    Nut with spines (Fagaceae)
    NA
    Wings on fruit
    there are no wings on the fruit

  • Glands or sap

    Sap color
    the sap is clear and watery
    Stalked glands on fruit (Rosa)
    NA

  • Growth form

    Growth form
    the plant is a tree

  • Leaves

    Hairs on underside of leaf blade
    the underside of the leaf has no hairs
    Hairs on upper side of leaf blade
    the upper side of the leaf is not hairy, or has very few hairs
    Leaf blade base shape
    the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
    Leaf blade base symmetry
    the leaf blade base is symmetrical
    Leaf blade bloom
    there is a noticeable powdery or waxy bloom on the underside of the leaf
    Leaf blade edges
    the edge of the leaf blade has teeth
    Leaf blade edges (Acer)
    NA
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    NA
    Leaf blade length
    100–220 mm
    Leaf blade scales
    there are no scales on the leaf blades
    Leaf blade shape
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is oblong (rectangular but with rounded ends)
    Leaf blade texture
    • the leaf blade is coriaceous (has a firm, leathery texture)
    • the leaf blade is herbaceous (has a leafy texture)
    Leaf blade translucent dots
    there are no translucent dots on the leaf blade
    Leaf blade vein pattern
    the main veins of the leaf blade are pinnate (the secondary veins branch off at intervals from the main central vein) and non-arcuate (not arched towards the leaf tip)
    Leaf blade veins
    the leaf blade has one main vein running from the base toward the tip
    Leaf blade width
    60–120 mm
    Leaf duration
    the leaves drop off in winter (or they wither but persist on the plant)
    Leaf form
    the plant is broad-leaved (with broadly flattened leaf blades)
    Leaf lobe tips (Quercus)
    NA
    Leaf midrib glands
    the midrib of the leaf blade has glands on the upper surface
    Leaf stalk
    the leaves have leaf stalks
    Leaf stalk attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk nectaries
    there are no nectaries on the leaf stalk
    Leaf stalk shape
    the leaf stalk is not flattened
    Leaf teeth
    the leaf blade margin is serrate (with forward-pointing) or dentate (with outward-pointing) with medium-sized to coarse teeth
    Leaf teeth hairs (Carya)
    NA
    Leaf type
    the leaf blade is compound (i.e., made up of two or more discrete leaflets
    Leaves per node
    there is one leaf per node along the stem
    Specific leaf type
    the leaf is compound, with a single terminal leaflet and more than two additional leaflets
    Stipules
    the plant has stipules

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • alpine or subalpine zones
    • forests
    • mountain summits and plateaus
    • ridges or ledges
    • swamps

  • Scent

    Plant odor
    the plant does not have much of an odor, or it has an unpleasant or repellant odor

  • Stem, shoot, branch

    Aerial roots
    the plant has no aerial roots
    Bark texture
    the bark of an adult plant is thin and smooth
    Branch brittleness (willows only)
    NA
    Branch cross-section
    the branch is circular in cross-section, or it has five or more sides, so that there are no sharp angles
    First-year cane (Rubus)
    NA
    Lenticels on twigs
    there are clearly lenticels on the twigs
    Pith shape
    the outline of the pith in a twig is roughly round
    Short shoots
    there are no peg- or knob-like shoots present
    Twig bloom
    there is no bloom on the twig
    Twig hairs
    the twigs have few or no hairs on them
    Twig papillae (Vaccinium species only)
    NA
    Twig scales
    there are no scales on the twig surface
    Twig winter color
    • brown
    • gray
    • red
    Wings on branch
    the branch does not have wings on it
    armature on plant
    the plant does not have spines, prickles, or thorns

Wetland status

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
absent
Vermont
present

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Maine
unranked (S-rank: SNR)
Massachusetts
fairly widespread (S-rank: S4)

From Flora Novae Angliae dichotomous key

2.  Sorbus americana Marsh. N

American mountain-ash. Pyrus americana (Marsh.) DC. • CT, MA, ME, NH, VT. Temperate, boreal, and subalpine forests, ridge tops, swamps. George (1999) reported this species from RI; however, all specimens seen by me identified as this species from RI either are Sorbus aucuparia or were collected from residential settings.

Native to North America?

Yes

Sometimes confused with

Sorbus aucuparia:
branchlets, inflorescence, winter bud scales, and lower surface of leaflets hairy (vs. S. americana, with branchlets, inflorescences, winter bud scales, and lower surface of leaflets without hairs or with very sparse hairs).
Sorbus decora:
leaflets 2-3.5 times as long as wide, winter bud scales ciliate along the edges, petals 4-5 mm long, and fruit 7-10 mm in diameter (vs. S. americana, with leaflets 3-5 times as long as wide, winter bud scales not or very sparsely ciliate along the edges, petals 3-4 mm long, and fruit 4-7 mm in diameter).

Synonyms

  • Pyrus americana (Marsh) DC.

Family

Rosaceae

Genus

Sorbus