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Hydrangea arborescens — American hydrangea

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Facts

American hydrangea (aka smooth hydrangea) is a deciduous shrub that grows to 5 feet (1.5 m) tall. Native to most of eastern North America, the few populations in New England are considered introduced, as they are mostly recorded from disturbed areas. Its clusters of smallish, white flowers are modest in comparison to more showy cultivated hydrangeas, but bloom for a long time. Plus, the plants are tolerant of poor soil conditions and can thrive in rain gardens and are useful for erosion control.

Habitat

Anthropogenic (man-made or disturbed habitats), floodplain (river or stream floodplains), forest edges, forests

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
New England state
  • Connecticut
  • Massachusetts
  • Vermont
Growth form
the plant is a shrub (i.e., a woody plant with several stems growing from the base)
Leaf type
the leaf blade is simple (i.e., lobed or unlobed but not separated into leaflets)
Leaves per node
there are two leaves 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
60–200 mm
Leaf blade width
Up to 120 mm
Leaf stalk
the leaves have leaf stalks
Fruit type (general)
the fruit is dry and splits open when ripe
Bark texture
the bark of an adult plant is thin and smooth
Twig winter color
  • brown
  • orange
  • 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
    Superposed buds
    there are no superposed buds on the branch

  • Flowers

    Carpels fused
    the carpels are fused to one another
    Enlarged sterile flowers
    some of the flowers on the plant are enlarged and sterile
    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 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)
    Sepal cilia (Ilex)
    NA
    Stamen number
    10
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are not fused to one another

  • Fruits or seeds

    Berry color
    NA
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release 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 shrub (i.e., a woody plant with several stems growing from the base)

  • Leaves

    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 cordate (heart-shaped, with rounded lobes)
    • the base of the leaf blade is rounded
    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
    60–200 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 ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade width
    Up to 120 mm
    Leaf duration
    the leaves drop off in winter (or they wither but persist on the plant)
    Leaf lobe tips (Quercus)
    NA
    Leaf stalk
    the leaves have leaf stalks
    Leaf stalk nectaries
    there are no nectaries on the leaf stalk
    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 simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaves per node
    there are two leaves 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
    • Connecticut
    • Massachusetts
    • Vermont
    Specific habitat
    • edges of forests
    • forests
    • man-made or disturbed habitats
    • river or stream floodplains

  • 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
    Twig papillae (Vaccinium species only)
    NA
    Twig winter color
    • brown
    • orange
    • 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

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

In New England

Distribution

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

Conservation status

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

Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

1.  Hydrangea arborescens L. E

American hydrangea. Hydrangea arborescens L. var. oblonga Torr. & Gray; H. arborescens L. var. sterilis Torr. & Gray • CT, MA, VT. Roadsides, forest borders and fragments, river banks, areas of cultivation.

Native to North America?

Yes and no (some introduced)

Sometimes confused with

Hydrangea cinerea:
leaf blades uniformly pubescent across the abaxial surface (vs. H. arborescens, with leaf blades nearly glabrous abaxially or sparsely hirsute along the midrib and sometimes the main lateral veins as well).
Hydrangea paniculata:
cymes panicle-like, pyramidal or ovoid, ovary half-inferior, and winter buds appressed and pointing forward (vs. H. arborescens, with cymes corymb-like, flat-topped or slightly convex, ovary completely inferior, and winter buds projecting outward from twig).

Synonyms

  • Hydrangea arborescens L. var. oblonga Torr. & Gray
  • Hydrangea arborescens L. var. sterilis Torr. & Gray

Family

Hydrangeaceae

Genus

Hydrangea