Quercus macrocarpa Michx.

burr oak

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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

Burr oak is mostly a tree of prairie edges, and is uncommon in New England. It produces the largest acorns of all the oaks, nearly the size of golf balls. Being exceptionally tolerant of drought, this tree is often used in roadside plantings and shelterbelts.

Habitat

Floodplain (river or stream floodplains), forests, swamps

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 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 lobes, or it has both teeth and lobes
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
50–310 mm
Leaf blade width
40–160 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
  • yellow
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 clustered near the tip of the twig
    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 stalks
    the winter buds have no stalks
  • Flowers
    Anther color
    the anthers show no hint of a pink, reddish or purplish tint
    Carpels fused
    the carpels are fused to one another
    Enlarged sterile flowers
    there are no enlarged sterile flowers on the plant
    Flower petal color
    NA
    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 does not have a hypanthium
    Inflorescence hairs
    there are no hairs on the inflorescence
    Inflorescence position
    the inflorescences grow on the twigs
    Inflorescence type
    • the inflorescence has only one flower on it
    • the inflorescence is an ament (catkin; slender, usually pendulous inflorescence with crowded unisexual flowers)
    Number of pistils
    1
    Ovary position
    the ovary is below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes only one cycle of petals or sepals
    Petal appearance
    NA
    Petal fusion
    NA
    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
    Sepals fused only to sepals
    • the sepals are fused to each other (not other flower parts), at least near their bases
    • the sepals are separate from one another
    Stamen number
    • 1 or 2
    • 10
    • 11
    • 12
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    • 9
    Stamen position relative to petals
    NA
    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 but does not split open when ripe
    Fruit type (specific)
    the fruit is a nut (dry and indehiscent, with a hard wall, usually containing only one seed and usually subtended by an involucre)
    Nut with spines (Fagaceae)
    the involucre has no spines
    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 hairs on it
    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 cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
    • the base of the leaf blade is rounded
    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 lobes, or it has both teeth and lobes
    Leaf blade edges (Acer)
    NA
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    • at least some of the hairs on the leaf blade are branched
    • the leaf blade has tangled or woolly-looking hairs, without glands
    Leaf blade length
    50–310 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)
    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
    40–160 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)
    the lobes of the leaf blade are rounded or bluntly pointed
    Leaf midrib glands
    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)
    • 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 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
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • forests
    • river or stream floodplains
    • 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
    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 ouline of the pith in a twig is roughly star-shaped, with several points or arms radiating from the center
    Pith type
    the pith inside the twig is solid, completely filled with spongy tissue
    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 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
    • red
    • yellow
    Wings on branch
    • the branch does not have wings on it
    • the branch has wings running along 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)

New England Distribution and Conservation Status

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.

Connecticut
unrankable (S-rank: SU), special concern (code: SC)
Massachusetts
uncommon (S-rank: S3), special concern (code: SC)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Rhode Island
historical (S-rank: SH), state historical (code: SH)

Native to North America?

Yes and no (some introduced)

Sometimes Confused With

Quercus bicolor:
leaf blade without deep sinuses near or below the middle of the blade and stalk of nut mostly 40-70 mm long (vs. Q. macrocarpa, with the leaf blade usually with 1 or more sinuses near or below the middle of the blade that extend more than 1/2 way from the tips of the lobes to the midvein and stalk of nut mostly 6-20 mm long).

Synonyms

  • Quercus macrocarpa var. depressa (Nutt.) Engelm.
  • Quercus mandanensis Rydb.

Family

Fagaceae

Genus

Quercus

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Information from Dichotomous Key of Flora Novae Angliae

7.  Quercus macrocarpa Michx. N

burr oak. Quercus macrocarpa Michx. var. depressa (Nutt.) Engelm.; Q. mandanensis Rydb. 
• CT, MA, ME, NH, VT; also reported from RI by Seymour (1982), but specimens are unknown. Swamps, riparian and lacustrine forests, also found on dry-mesic to mesic soil of forests in regions of high-pH bedrock (e.g., VT). This species is sometimes confused with Quercus 
bicolor given they often grown in similar locations. In addition to characters used in the identification key, peduncle length will assist with determinations: (0–) 6–20 (–25) mm long 
in Q. macrocarpa and (20–) 40–70 mm long in Q. bicolor.

1×7. Quercus alba × Quercus macrocarpa Quercus ×‌bebbiana Schneid. is a very rare oak hybrid known from CT, VT. This nothospecies shows varying degrees of intermediacy between the parental taxa, especially in leaf blade outline.

1 ×8. Quercus ×‌saulii Schneid. is a rare oak hybrid known from CT, MA, RI, VT. The leaf blades most resemble Q. montana; however, the lobes are more pronounced and the sinuses between them are deeper.

1 ×12. Quercus ×‌faxonii Trel. is a very rare oak hybrid known from MA. It displays intermediacy in leaf blade outline and pubescence and peduncle length (see identification key for details). In the absence of fruits, specimens of this hybrid can be confused with Quercus ×‌saulii (1 ×8).

2×7. Quercus bicolor × Quercus macrocarpa Quercus ×‌schuettei Trel. is a very rare oak hybrid known from VT. It is primarily known from the lacustrine floodplain of Lake Champlain where both parents grow together. The hybrid’s leaves are generally a little smaller and show less prominent lobes than those of Q. macrocarpa. Further, the pubescence of the leaf blades is less dense and not as persistent as that of Q. bicolor.