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''Quercus macrocarpa'', the bur oak, 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 central United States and eastern and central Canada. This plant is also called mossycup oak and mossycup white oak. ''Quercus macrocarpa'' is widespread in the Atlantic coastal plain from New Brunswick to North Carolina, west as far as Alberta, eastern Montana, Wyoming, and northeastern New Mexico. The vast majority of the populations are found in the eastern Great Plains, the Mississippi/Missouri/Ohio Valley, and the Great Lakes region.〔(Biota of North America Progrram 2014 county distribution map )〕 ==Description== ''Quercus macrocarpa'' is a large deciduous tree growing up to 100 ft (30 m), rarely 130 ft (40 m), in height, and is one of the most massive oaks with a trunk diameter of up to 10 ft (3 m); reports of taller trees occur, but have not been verified. It is one of the slowest-growing oaks, with a growth rate of 1 ft (30 cm) per year when young. A 20-year-old tree will be about 20 ft (6 m) tall. It commonly lives to be 200 to 300 years old, and may live up to 400 years.〔http://www.ldeo.columbia.edu/~adk/oldlisteast/Spp/QUMAC.html Eastern OLDLIST〕 The bark is a medium gray and somewhat rugged.〔 The leaves are 3–6 in (7–15 cm) long and 2–5 in (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, 0.75–2 in (2–5 cm) long and 0.75-1.5 in (2–4 cm) broad, having 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, both of which it occasionally hybridizes with. ;Acorns The acorns are the largest of any North American oak (thus the Latin species name ''macrocarpa''—large fruit), 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 evolutionary 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.〔(Flora of North America: ''Quercus macrocarpa'' )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quercus macrocarpa」の詳細全文を読む スポンサード リンク
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