Bur oak

Taxobox
name = Bur Oak
status = LR/lc | status_system = IUCN2.3

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 (100 ft), rarely 37 m (120 ft), in height, and is one the most massive oaks with a trunk diameter of up to 3 m (10 ft); reports of taller trees occur, but have not been verified. It is one of slowest-growing oaks, with growth rate of 30 cm (1 ft) per year when young. A 20-year-old tree will be about 6 m (20 ft) tall. It commonly lives to be 200 to 300 years old, and may become significantly older. The bark is a medium gray and somewhat rugged.

The leaves are 7-15 cm (3-6 in) long and 5-13 cm (2-5 in) 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 (0.8-2 in) long and 2-4 cm (0.8-1.5 in) 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.

Ecology

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.

Cultivation and uses

Bur oak makes an outstanding ornamental tree. It is one of the most tolerant of urban conditions of the white oaks, and is one of the fastest-growing of the group. It has been planted in many places north to Anchorage, Alaska and as far south as Edinburg, 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

References

*
* [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501058 Flora of North America: "Quercus macrocarpa"]
* [http://plants.usda.gov/java/profile?symbol=QUMA2 USDA Plants Profile: "Quercus macrocarpa"]
* [http://www.cas.vanderbilt.edu/bioimages/species/frame/quma2.htm "Quercus macrocarpa" images at bioimages.vanderbilt.edu]