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

Rhododendron maximum — great rosebay, rhododendron

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Facts

Great rosebay is a dramatically beautiful understory shrub of moist forests and hemlock-dominated swamps throughout the Appalachian belt. In the wild, its flowers range from pink to white, topping tangles of branches that bear large, leathery leaves. In cold temperatures, these leaves roll up to prevent desiccation damage. Great rosebay recovers easily from mild fires because it spreads by layering and suckering. As such, it is used to reclaim disturbed sites and prevent erosion. Dense thickets can slow the pace of recovery to mature forest by shading out tree seedlings and reducing earthworm densities in the soil. They also provide cover and shelter for deer, bears, and bird species. Many cultivars are available to gardeners.

Habitat

Forests, shores of rivers or lakes, 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
wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • 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 is one leaf per node along the stem
Leaf blade edges
the edge of the leaf blade has no teeth or lobes
Leaf duration
the leaves remain green all winter
armature on plant
the plant does not have spines, prickles, or thorns
Leaf blade length
100–200 mm
Leaf blade width
20–80 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 ridged or plated
  • the bark of an adult plant is thin and smooth
Twig winter color
  • brown
  • gray
  • green
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
    Winter bud scale hairs
    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 appearance
    the flowers appear after the leaves have appeared
    Flower petal color
    • red
    • white
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Hairs on ovary (Amelanchier)
    NA
    Hypanthium present
    the flower does not have 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 raceme (a long unbranched stem with stalked flowers growing along it)
    • the inflorescence is an umbel (with an axis so short it appears the flowers all originate from the same point)
    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 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 fused to form a tube, cup, or bell shape
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal cilia (Ilex)
    NA
    Sepal tip glands
    there are glands at the tips of the sepal lobes
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Stamens fused
    the stamens are not fused to one another

  • Fruits or seeds

    Berry color
    NA
    Fruit tissue origin
    there are no flower parts that form part of the fruit
    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 underside of leaf blade
    the underside of the leaf has hairs on it
    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
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    the edge of the leaf blade has no teeth or lobes
    Leaf blade edges (Acer)
    NA
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    the leaf blade has tangled or woolly-looking hairs, without glands
    Leaf blade length
    100–200 mm
    Leaf blade scales
    there are no scales on the leaf blades
    Leaf blade shape
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    Leaf blade texture
    the leaf blade is coriaceous (has a firm, leathery 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
    20–80 mm
    Leaf duration
    the leaves remain green all winter
    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
    • the midrib of the leaf blade lacks 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 edge of the leaf blade is entire (has no teeth or lobes)
    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
    Stipules
    there are no stipules on the plant, or they fall off as the leaf expands

  • Place

    Habitat
    wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • forests
    • shores of rivers or lakes
    • 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 ridged or plated
    • 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 no lenticels on the twigs, or they are very hard to see
    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
    • the twigs have hairs with glands at their tips
    • the twigs have hairs, but the hairs do not have glands
    Twig papillae (Vaccinium species only)
    NA
    Twig scales
    there are no scales on the twig surface
    Twig winter color
    • brown
    • gray
    • green
    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
present
Vermont
present

Conservation status

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

Connecticut
uncommon to fairly widespread (S-rank: S3S4)
Maine
extremely rare (S-rank: S1), threatened (code: T)
Massachusetts
extremely rare to rare (S-rank: S1S2), threatened (code: T)
New Hampshire
rare (S-rank: S2), threatened (code: T)
Vermont
rare (S-rank: S2), threatened (code: T)

From Flora Novae Angliae dichotomous key

8.  Rhododendron maximum L. N

great rosebay. CT, MA, ME, NH, RI, VT; unusual distribution with several well-known disjunct populations in the northern New England states. Evergreen to deciduous swamps, lake shores, forests.

Native to North America?

Yes

Sometimes confused with

Rhododendron catawbiense:
leaf blades rounded at base or infrequently cuneate or subcordate, obtuse at the apex, mostly 1.5–2.5 times as long as wide, sepals 0.5–1.7 mm long, and corolla usually largely pink to purple (vs. R. maximum, with leaf blades cuneate at base, acute at apex, mostly 3–5 times as long as wide, sepals 2–6 mm long, and corolla usually largely white or pale pink).
Rhododendron carolinianum:
leaf blades lepidote, especially on the abaxial surface; ovary lepidote (vs. R. maximum, with leaf blades not lepidote, ovary glabrous or pubescent with eglandular and/or glandular hairs, but not lepidote).

Family

Ericaceae

Genus

Rhododendron