Ulmus thomasii Sarg.

rock elm

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

Ulmus thomasii is a native tree that is centered in the Midwestern and Great Lakes region of the United States. It is distinctive in its irregular, corky wings found on the branches.

Habitat

Floodplain (river or stream floodplains), forests, ridges or ledges, swamps, woodlands

Characteristics

Habitat
terrestrial
New England state
  • New Hampshire
  • Vermont
Growth form
the plant is a tree
Leaf type
the leaf blade is simple (i.e., lobed or unlobed but not separated into 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
25–160 mm
Leaf blade width
25–50 mm
Leaf stalk
the leaves have leaf stalks
Fruit type (general)
the fruit is dry but does not split open when ripe
Bark texture
the bark of an adult plant is ridged or plated
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
  • Flowers
    Carpels fused
    the carpels are fused to one another
    Enlarged sterile flowers
    there are no enlarged sterile flowers on the plant
    Flower appearance
    the flowers appear before the leaves
    Flower petal color
    • purple
    • yellow or green
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Hairs on ovary (Amelanchier)
    NA
    Inflorescence position
    the inflorescences grow on older branches
    Inflorescence type
    • the inflorescence is a monochasial cyme (an axis with a terminal flower, below it a branch with a terminal flower, this branch may itself have a branch and so on)
    • the inflorescence is a raceme (a long unbranched stem with stalked flowers growing along it)
    Number of pistils
    1
    Ovary position
    the ovary is above the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes only one cycle of petals or sepals
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal fusion
    the perianth parts are fused to form a tube, cup, or bell shape
    Sepal appearance
    the sepals resemble petals in color and texture
    Sepal cilia (Ilex)
    NA
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Stamen number
    • 5
    • 6
    • 7
    • 8
    Stamen position relative to petals
    the stamens are lined up with the sepals (antesepalous)
    Stamens fused
    the stamens are not fused to one another
  • Fruits or seeds
    Berry color
    NA
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
    Nut with spines (Fagaceae)
    NA
    Wings on fruit
    the fruit has one or more wings on it
  • 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 upper side of leaf blade
    • the upper side of the leaf is fuzzy or hairy
    • 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 rounded
    Leaf blade base symmetry
    • the leaf blade base is asymmetrical
    • the leaf blade base is symmetrical
    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
    the hairs on the leaf blade are different from the choices given
    Leaf blade length
    25–160 mm
    Leaf blade scales
    there are no scales on the leaf blades
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade texture
    • the leaf blade is chartaceous (thin and dry like paper)
    • the leaf blade is herbaceous (has a leafy texture)
    Leaf blade translucent dots
    there are no translucent dots on the leaf blade
    Leaf blade width
    25–50 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 lacks glands on the upper surface
    Leaf stalk
    the leaves have leaf stalks
    Leaf stalk nectaries
    there are no nectaries on the leaf stalk
    Leaf teeth
    the leaf blade margin has teeth, which themselves have smaller teeth on them
    Leaf teeth hairs (Carya)
    NA
    Leaf type
    the leaf blade is simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaves per node
    there is one leaf per node along the stem
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
  • Place
    Habitat
    terrestrial
    New England state
    • New Hampshire
    • Vermont
    Specific habitat
    • forests
    • ridges or ledges
    • river or stream floodplains
    • swamps
    • woodlands
  • 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 ridged or plated
    Branch brittleness (willows only)
    NA
    First-year cane (Rubus)
    NA
    Twig papillae (Vaccinium species only)
    NA
    Twig winter color
    • brown
    • gray
    • red
    Wings on branch
    the branch has wings running along 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)

New England Distribution and Conservation Status

Distribution

Connecticut
absent
Maine
absent
Massachusetts
absent
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.

Massachusetts
unranked (S-rank: SNR)
New Hampshire
unrankable (S-rank: SU), Ind (code: Ind)
Vermont
extremely rare (S-rank: S1), threatened (code: T)

Native to North America?

Yes

Sometimes Confused With

Ulmus americana

Family

Ulmaceae

Genus

Ulmus

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Information from Dichotomous Key of Flora Novae Angliae

7.  Ulmus thomasii Sarg. NC

rock elm. NH, VT; also reported for CT by Magee and Ahles, but specimens are unknown. Woodlands and ledges in regions of high-pH bedrock, riparian forests, swamps.