Bur Oak (Blue Oak, Mossycup Oak)
Quercus macrocarpa Michx.
Chêne à gros fruits
Habitat 
The most common native white oak, found from southern Saskatchewan east to New Brunswick.
Leaves:
15-30 cm long; highly variable in shape.
Often has a broadly expanded, toothed portion above two deep notches, with a lower portion containing a few short, rounded lobes.
Some leaves resemble White Oak, with 7-9 deep lobes.
Upper surface shiny green, pale, and hairy underneath.
Stipules are often present.
Buds:
Terminal bud is 3-6 mm long, blunt-pointed, brown, and hairy.
Often surrounded by a few elongated, pointed scales.
Lateral buds are pressed against the twig.
Twigs:
Stout, yellowish-brown, somewhat hairy.
Branchlets often develop corky ridges.
Fruits:
Acorns are 20-30 mm long, usually solitary, and either stalkless or short-stalked.
Cup is large, enclosing at least half of the acorn.
Scales are knobby, long-pointed, with narrow free tips, forming a conspicuous fringed border.
Bark:
Rough, deeply furrowed, with ridges broken into irregular, thick, dark gray scales.
Wood:
Light brown.
Size and Form:
Small to medium-sized trees, up to 15 m high and 60 cm in diameter, but can live for 200 years or more.
Trunk is tall and straight, distinct up to the upper crown.
Principal branches ascend in the upper crown and are nearly horizontal in the lower crown.
New shoots (epicormic branches) often sprout along the trunk.
Trees growing in shallow, exposed soils may be stunted, with a trunk that divides into radiating, crooked, and gnarled branches.
Root system is deep and wide-spreading, with a strong taproot.
Habitat:
Prefers deep, rich bottomland soils.
Can also be found on upland limestone soils and, at the northern edge of its range, on shallow soils over granitic bedrock.
Grows in mixed forests with other species.
Drought-tolerant and moderately shade-tolerant.
Notes:
Fire-resistant due to its thick bark, allowing it to persist in grassland environments.
Readily transplants and is tolerant of urban conditions.
Hybridizes with Swamp White Oak.
Algonquin Park Population:
Very rare in Algonquin, found only along the Barron River system, from Squirrel Rapids to Grand Lake at Achray.
Despite its tolerance for cold and drought, it does not thrive well in Algonquin.
Likely due to the lack of clay-based soils, which it prefers.