Oak, also known as Quercus or Quercus, is a general term for FAGACEAE plants, including species of Quercus, Cyclobalanopsis and Coe, and usually refers to Quercus plants rather than a specific tree species. There are 6 15 species of Quercus, of which 450 species are from Quercus subgenus, and 188 is Quercus subgenus. Its fruit is called acorn, and its wood is generally called oak. Oak is the largest flowering plant in the world; Life is very long, it has a life span of 400 years. The fruit is nuts, hairy at one end and bare at the other end, which is beautiful and delicious (people generally don't eat it). It is the first-class food for squirrels and other animals. It is found that a Jurupa oak tree in California, USA has survived for at least 6.5438+0.3 million years, which may be the oldest known creature in the world. Xinhua News Agency, April 30, 2006, at 5438+0, the American Arbor Day Foundation recently announced that the oak tree was selected as the national tree of the United States through public network voting.