Bur oak

Silhouette - bur oak
  • Latin name: Quercus macrocarpa Michx.
  • French name: Chêne à gros fruits
  • Synonym(s): Mossycup oak , blue oak
  • Taxonomic Serial Number: 19287
Description

Leaves

  • Leaf form - bur oak
  • Leaf form - bur oak
  • Leaf form - bur oak

Form

  • Variable in shape
  • Often with a broadly expanded toothed portion above 2 deep notches
  • Lower portion with a few short, rounded lobes
  • Other leaves resemble white oak, with 7–9 deep lobes
  • Stipules often present
  • Lower surface hairy

Length

  • 15–30 cm

Colour

  • Upper surface shiny green
  • Lower surface paler

Buds

  • Lateral bud and leaf scar - bur oak

Form

  • Terminal bud blunt-pointed, hairy
  • Often surrounded by a few elongated, pointed scales
  • Lateral buds pressed against the twig

Length

  • Terminal bud 3–6 mm

Colour

  • Brown

Twigs

  • Winter twig - bur oak

Form

  • Stout, somewhat hairy
  • Branchlets often with corky ridges

Colour

  • Yellowish-brown

Flowers

Form

  • Pollen flowers small
  • In many-flowered drooping catkins
  • Seed flowers small
  • Solitary or in few-flowered clusters (spikes)

Structure

  • Monoecious

Floral timing

  • With the leaves

Fruits

  • Acorn - bur oak

Form

  • Acorns usually solitary
  • Stalkless or short-stalked
  • Cup large, enclosing one-half or more of the acorn
  • Scales knobby, long-pointed, with narrow free tips
  • Forming a conspicuous fringe to the cup

Length

  • Acorns 20–30 mm

Structure

  • 1-seeded nut

Bark

Form

  • Rough becoming deeply furrowed with ridges broken into irregular thick scales

Colour

  • Dark grey

Wood

Colour

  • Light brown

Size

Height

  • To 15 m

Diameter

  • To 60 cm

Maximum age

  • 200 years

Tree form

  • Silhouette - bur oak

Forest-grown

Trunk

  • Straight, tall
  • Distinct to the upper crown
  • Epicormic branches often occur along the trunk

Crown

  • Principal branches ascending in the upper crown
  • Nearly horizontal in the lower crown
  • May be stunted on shallow soils
  • Trunk divides into radiating, crooked branches

Root system

  • Deep, wide-spreading, with a deep taproot

Habitat

Site

  • Deep, rich bottomlands
  • Upland limestone soils
  • Grasslands
  • Shallow soils over granitic bedrock (at northern limits of range)
  • Tolerates urban sites

Light tolerance

  • Moderately shade-tolerant

Associated species

  • Mixed with various other species

Range

Southern Saskatchewan east to New Brunswick

Photos
  • Bur oak
  • Bur oak
  • Bur oak
  • Bur oak
  • Bur oak
  • Bur oak
  • Bur oak
  • Bur oak
Distribution map
Distribution map - bur oak
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