Within the 90 species of native and naturalized oak trees found in North America, there are three different types: red, white and golden. The differences between red and white oaks are in the composition of the wood and how long the acorns take to reach maturity. The fruit of the oak tree is the acorn.
Red oaks are also known as black oaks. In red oaks, the underbark and heartwood are red or orange. The dark gray to black bark ranges from smooth to deeply grooved. The tips of red oak leaves--which are both lobed and unlobed--have bristles. Red oaks are found in both the eastern and western halves of the United States. Red oak species include the Arkansas oak, Florida oak, bear oak and pin oak in the East and coast live oak, interior live oak and California black oak in the West.
White oaks have white or tan underbark and heartwood. The bark is pale gray and ranges from smooth to flaky or scaly. The edges of white oak leaves--which are lobed and unlobed, sometime on the same tree--are smooth. White oaks are also found on both sides of the country and include the chestnut oak, Southern live oak and burr oak in the East and the Arizona oak, gray oak and valley oak in the West.
The golden oak group is found in the West and includes the canyon live oak, Palmer oak and Channel Island oak. The huckleberry oak is also a golden oak but at 2 to 4 feet, it is considered a shrub, according to the United States Department of Agriculture Forest Service. Golden oak bark ranges in color from dark gray to pale gray and ranges from smooth to grooved. The leaves are evergreen, not lobed and have toothed edges.
In oak trees, both male and female flowers appear on the same tree, blooming near developing twigs on the branches. Both male and female flowers are generally yellow-green in color and bloom in the early spring. The female flowers are small and unnoticeable, often grouped in oblong clusters but sometimes blooming singly. The male flowers hang from the branches as catkins, ranging up to 2 inches in length. The male flowers release large amounts of pollen.
The acorn is comprised of a nut encased in a scaly cup called a cupule. Red oak acorns are smaller than white oak acorns and they mature in alternate years, according to the University of Florida Extension. White oak acorns are lower in tannins than red oak acorns and drop every year. Golden oak acorn cups are covered in golden hair, which is how the tree received its name, according to the "Field Guide to Trees of North America" by the National Wildlife Federation.