"Mighty oaks from little acorns grow," goes the familiar saying, but identifying which oak comes from what acorn is another question. The term "acorn" comes from the Old English word "aecern," which means berry or fruit, and the acorn -- also called oak mast -- is the fruit of the oak tree. Although acorns generally resemble one another, each species of oak produces slightly different acorns. With a few basic ground rules, you can readily link acorns to one of the two main families of oak trees: red or black oaks (Erythrobalanus) and white oaks (Leucobalanus).
Visit a forest or park where a variety of oak trees grow. Go in spring or fall. Locate an oak tree by the presence of acorns in the tree or on the ground below.
Pick up an acorn from the ground or pluck one from the tree. Pull off the cap of the acorn and inspect the inside of the cap. If it is smooth inside, without hair, it comes from a white oak tree. Red oak acorns have woolly hair on the inside of the acorn cap.
Look for germinating acorns on the ground under the oak tree or nearby. Many acorns turn red just before germinating and are easy to spot. If you find germinating acorns in spring, the tree belongs to the red oak family. White oak acorns germinate in fall.
Break the acorn in two pieces and nibble the inner nut. White oaks have sweet-tasting acorns while red oak acorns contain more tannin and are bitter.
Confirm your identification by looking at other features of the oaks. Inspect a leaf. If you see bristles between the lobes, the tree is a member of the red oak family. Look closely at the bark color. Most red oaks have dark bark, gray, brown or black, while white oaks have lighter bark. If you visit in the fall and the leaves of the oak are red, you are looking at a red oak; it is from autumn leaf color that the family got the name.