Bur oak
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| Bur Oak Conservation status: Secure | ||||||||||||||
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| Missing image Quercus_macrocarpa.jpg Bur Oak leaves and acorns | ||||||||||||||
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The Bur oak (Quercus macrocarpa), native to the midwestern United States and south-central Canada, grows to be one of North America's most massive oaks. For instance, the West Virginia state champion has a trunk diameter of almost 3 metres (9 feet). It is also one of fastest-growing of the white oaks (section Quercus), with growth rates of 60-100 cm/year when young. It commonly lives to be 200 to 300 years old, and may become significantly older. It grows up to 30m, rarely 37m, in height; reports of taller trees occur, but have not been verified.
Its range is generally 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.
The Bur oak is a tree that prefers to grow in the open, away from forest canopy. For this reason, it is an important tree on the eastern prairies and is often found near waterways in more forested areas, where there is a break in the canopy. It is also a fire-resistant tree.
Its wood is high quality, and is almost always marketed as "white oak".
The leaves are entire and variously lobed, being highly variable in shape. Most often, the top forty percent of the leaf has shallow lobes or large teeth and is wider, while the bottom sixty percent is narrower and deeply lobed. The bark is a medium gray and somewhat rugged. The tree possesses significant drought resistance by virtue of a lengthy taproot. New trees may, after two to three years of growth, possess a 1 to 2 meter deep taproot.
The acorns are the largest of any native North American oak and are an important wildlife food, although only borne heavily every few years. They are distinctive in having large caps that wrap much of the way around the nut, with large overlapping scales and often a fringe at the edge of the cap.
The Bur oak makes an outstanding shade tree. It is one of the most tolerant of urban conditions of the white oaks, and has been planted as a street tree in many places.
Sometimes the name is spelled "Burr oak", as for example in Burr Oak State Park in Ohio.
It is sometimes confused with the Overcup oak and the White oak.
External links
- Flora of North America: Quercus macrocarpa (http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501058)