Most oaks live for 200 to 400 years. Oaks are an important source of lumber. Oak wood is heavy, hard, and strong, and it has a beautiful grain. Manufacturers use it for furniture, barrels, and railroad ties. The wood and bark of some oaks contain tannin, a bitter substance used in the preparation of leather.
Cork comes from the bark of certain oaks.
Acorns are an important source of food for wildlife. In the past, many Indians of North America used acorns for food. Today, oaks are grown as ornamental trees worldwide. The white oak is common in eastern North America. It has grayish bark and leaves with seven or nine lobes.