Oak trees (genus Quercus) belong to the beech family (Fagaceae) of plants. Defining an oak's age at maturity is difficult given the various definitions the word may have. As examples, the United States Department of Agriculture defines the maturity of an oak as the age when it begins flowering, but the Missouri Department of Conservation defines maturity as the time when a tree reaches its intended size based upon its intended use. Thus, the term "maturity" may have more than one meaning.
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Northern Red Oak
The northern red oak (Quercus rubra) reaches the initial stages of sexual maturity after 20 to 25 years of growth. This is when the tree will begin flowering and producing crops of acorns, though large acorn crops will not occur until the tree is about 50 years old. But, a northern red oak can well afford to take its time, as under optimal growing conditions an individual tree might live for 500 years.
White oak (Quercus alba) is a slower growing member of the oak species. According to the United States Forest Service, a white oak may not begin flowering and producing acorns for as long as 200 years. That's a long time to wait if you happen to be a hungry squirrel. Like the northern red oak, white oaks have long lifespans. White oaks can live for as long as 600 years, meaning white oaks still living as of 2011, may have begun producing acorns about the time the Pilgrims arrived.
The black oak (Quercus velutina) shares most of its native growing range with both northern red oak and white oak, meaning the eastern half of the U.S. Black oaks reach sexual maturity fairly early, producing a first crop of acorns in as little as 20 years. And while not as long lived as its red or white cousins, even if growing in poor quality soils, a black oak may survive for 200 years.
Shumard oak (Quercus shumardii) is one of largest oaks found growing in the southeastern portion of the U.S. The tree reaches initial sexual maturity after about 25 years, though peak acorn production does not usually occur for another 25 years. A Shumard oak may grow as tall as 110 feet in height. The oldest specimen on record lived to the ripe old age of 480 years.