Origin: North America (native in Ontario)
Bur oak is a small tree with a straight trunk. Upper branches grow upward while lower branches grow horizontally.Read more about Tree, Bark, Twigs
Leaves are 15 - 30 cm (6" - 12") long with variable irregular lobes.Read more about Leaves
Male and female flowers are borne separately on the same tree, the tiny male flowers clustered in dangling catkins.Read more about Flowers
Fruits are acorns with cups bordered with a bur-like fringe.Read more about Fruit
Bur oak is a small to medium tree, up to 18 m (60') or more in height with a straight trunk. Upper branches grow upward while lower branches grow horizontally.
Twigs are hairy with corky ridges and hairy, brown, blunt-tipped buds. Terminal buds are 3 - 6 mm (1/8" - 1/4") long.
Leaves are 15 - 30 cm (6" - 12") long with variable, irregular, mostly rounded lobes without bristle-tips.
Most leaves are broadest in the upper half and taper to a narrow base. The two halves are usually separated by deeply cut sinuses.
Fruits are acorns 2 - 3 cm (3/4" - 1 1/8") long, with a pointed tip. Each acorn consists of a nut, at least half of which is covered by its cup, which has a burr-like fringe.
Bur oak is native to North America, its range extending from the Maritimes to the Canadian prairies, south through the midwestern states to Texas. It is the most common, widespread oak species in Canada. It is adapted to a variety of habitats ranging from dry prairie to moist bottomlands. The thick bark allows bur oaks to survive the natural fires that sustain prairie ecosystems while its deep and wide-spreading roots allow it to access moisture in dry environments and thus survive droughts.
Bur oak is capable of living up to 300 years.
Oaks are divided into two main groups primarily by their leaf shape. Trees in the red oak group have leaves with pointed, bristle-tipped lobes while those in the white oak group have either unlobed leaves with large teeth or leaves with rounded lobes
Bur oak belongs to the white oak group, along with white oak (Quercus alba), swamp white oak (Quercus bicolor), and English oak (Quercus robur). Bur oak is fairly easy to distinguish by its fringed acorn and by its leaves, which though variable in shape, are usually widest above the middle, with the upper and lower halves separated by deeply cut sinuses.
Bur oak is the state tree of Iowa.
Derivation of names
The genus name, Quercus, is the classical Latin name for the oaks. The species name, macrocarpa, means "with large fruit," from the Greek makros, meaning large, and karpos, meaning fruit. The common name, bur oak, refers to the burr-like bristles on the acorn cup. The alternative common name, mossycup oak, also derives from the bristles on the cup.
Bur oak acorns were an important source of food for Aboriginal peoples and have been found in archaeological excavations dating back at least 5,000 years. Bur oak wood is classed as white oak by the timber industry because the wood of the two species is very similar and used for the same purposes, namely, panelling, furniture, flooring, and wine barrels.
Bur oak acorns provide food for many mammals and birds including white-tailed deer, red squirrels, ducks, and various species of rodent.
Bur oak's place in Toronto's urban forest
Bur oak is seen more frequently in Toronto now as part of a trend to plant a variety of native species in the urban forest.
Landscape value and potential for home planting
Bur oak is more tolerant of urban conditions than most species of oak. It is quite drought resistant and has proven to be tolerant of pollution, making it suitable for many urban planting situations. It is, however, difficult to transplant. It grows best in sunny sites.
Pests and diseases: Bur oak is affected by the same pests and diseases that affect white oak (Quercus alba). These include gypsy moth (Lymantria dispar), an insect that is native to Europe and Asia. Gypsy moth caterpillars feed on new leaves, often defoliating the whole tree and leaving a tell-tale white frass that hangs from infested trees. If only one defoliation occurs, the tree can recover, but will be weakened; if a tree is repeatedly defoliated, it may die. The City conducts aerial spraying in years predicted to have heavy infestations of gypsy moth. For more information on pests affecting bur oak, see Natural Resources Canada factsheet.
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