Bur oak

Leaves

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

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

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

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

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