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For places named after the oak, see Burr Oak.

Bur Oak
Bur Oak leaves and acorn
Conservation status
Least Concern
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Fagales Family: Fagaceae Genus: Quercus Section: Quercus Species: Q. macrocarpa
Binomial name
Quercus macrocarpa Michx.

The Bur Oak, (Quercus macrocarpa), sometimes spelled Burr Oak, is a species of oak in the white oak section Quercus sect. Quercus, native to North America in the eastern and midwestern United States and south-central Canada. This plant is also called Mossycup oak and Mossycup white oak. It occurs from the Appalachian Mountains west to the middle of the Great Plains, extending to central Texas, across southernmost Manitoba, Ontario and Quebec, east to the Atlantic Coast in southern New Brunswick, and down the coast to Delaware. Bur Oak is the state tree of Iowa.

It is a large deciduous tree growing up to 30 m, rarely 37 m, in height, and is one the most massive oaks with a trunk diameter of up to 3 m; reports of taller trees occur, but have not been verified. It is also one of fastest-growing oaks, with growth rates of 60-100 cm per year when young. It commonly lives to be 200 to 300 years old, and may become significantly older. The bark is a medium gray and somewhat rugged.

Acorns

The leaves are 7-15 cm long and 5-13 cm broad, variable in shape, with a lobed margin. Most often, the basal 60% is narrower and deeply lobed, while the apical 40% is wider and has shallow lobes or large teeth. The flowers are greenish-yellow catkins, produced in the spring. The acorns are very large, 2-5 cm long and 2-4 cm broad, with a large cup that wraps much of the way around the nut, with large overlapping scales and often a fringe at the edge of the cup.

Bur Oak is sometimes confused with Overcup oak and White oak.

Bur Oak typically grows in the open, away from forest canopy. For this reason, it is an important tree on the eastern prairies, where it is often found near waterways in more forested areas, where there is a break in the canopy. It is also a fire-resistant tree, and possesses significant drought resistance by virtue of a long taproot. New trees may, after two to three years of growth, possess a 1-2 m deep taproot. The West Virginia state champion Bur Oak has a trunk diameter of almost 3 m (9 feet).

The acorns are the largest of any North American oak, and are an important wildlife food; American Black Bears sometimes tear off branches to get them. However, heavy nut crops are borne only every few years. In this strategy, known as masting, the large seed crop every few years overwhelms the ability of seed predators to eat the acorns, thus ensuring the survival of some seeds. Other wildlife, such as deer and porcupine, eat the leaves, twigs and bark. Cattle are heavy browsers in some areas. The bur oak is the only known foodplant of Bucculatrix recognita caterpillars.

Bur Oak makes an outstanding ornamental tree. It is one of the most tolerant of urban conditions of the white oaks, and has been planted in many places such as Anchorage, Alaska and San Antonio, Texas. It withstands chinook conditions at Calgary, Alberta.

The wood is high quality, and is almost always marketed as "white oak".

The name sometimes is spelled "burr oak", as for example in Burr Oak State Park in Ohio, the city of Burr Oak, Kansas, the village of Burr Oak, Michigan, and in the title Burr Oaks by poet Richard Eberhart.

It is also less commonly called "burl oak," as in the Burl Oaks Country Club in Mound, Minnesota, and the Burl-Oak Theatre Company in Oakville, Ontario

Wikimedia Commons has media related to:

Quercus macrocarpa

• Sternberg, G. (1998). Quercus macrocarpa. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 06 May 2006.
• Flora of North America: Quercus macrocarpa
• USDA Plants Profile: Quercus macrocarpa
• Quercus macrocarpa images at bioimages.vanderbilt.edu