Acorns come in many varieties and are found throughout the United States. Unlike apples, which grow on apple trees, or walnuts, which grow on walnut trees, acorns do not share the name of the tree on which they grow. Though sometimes referred to mistakenly as an "acorn tree," the tree that produces acorns is the oak.
Several species of oak (Quercus) can be found throughout the United States. Naturalists divide oaks into three broad groups, classifying individual species as red oak, black oak or white oak. In general, oak trees are tall, with many species growing to heights of up to 100 feet. They have true end buds, which means the bud lies on the end of a twig, and produce acorns. Individual species of oak can be identified by leaf, bark, bud, twig and fruit characteristics.
Types of Acorns
Individual acorn characteristics differ depending on species of oak. In general, red oak acorns have flat and saucer-shaped caps with overlapping scales; black oak acorn caps are bowl-shaped and shaggy; and white oaks bear acorns that have bumpy, bowl-shaped caps. Acorns vary widely from species to species within the broad categories. Acorns of the northern red oak, for instance, are less than an inch in length and egg-shaped, while acorns of the sawtooth oak, also a red oak, are larger, measuring more than an inch in diameter, with unusual caps with scales that grow long and curl.
Food for Wildlife
Many wildlife species depend on acorns for food. Deer, mice, wild pigs, blue jays and woodpeckers feed on the fruits once they drop to the ground. During years when acorns are scarce, these animals will find other food sources. Some animal species, however, entirely depend on acorns for their survival. Acorn woodpeckers, for instance, rely solely on acorns and will migrate to another area should the nuts become unavailable.
Food for Humans
Acorns have served as a source of food for humans for thousands of years. They were a staple of many Indian tribes in Northern America. Many species of oaks produce acorns that are edible raw. Acorn leaching, a process that leaches tannins from the nuts using hot water, decreases bitterness and makes the nuts easier to digest. Acorns can be ground into meal for use in breads and stews or processed into oil.