Acorns are the fruit of the oak tree (Quercus genus). Each acorn is an edible nut inside a tough shell, called a cupule. Acorns are usually brown or tan, but they may be light in color and have a wide variety of shapes, sizes, and types of cups. The shape of acorns and the type of cupule can help identify different species of oak trees in a landscape.
For example, black oak (Quercus velutina) produces acorns that are broadly rounded in shape with a thin tan, scaly cap covering half of the nut. The leaves of this species of oak tree are long and narrow with lobes that resemble bristles along the margins. Cherrybark oak (Quercus pyrobalana) is another species of oak that is identifiable by its acorns and large, ovate leaves with rounded, bristle-tipped lobes.
It is important to avoid acorns that show signs of insect damage or rot. Bruising or rot indicates that the acorn will be inedible, and it may harbor insects or disease-causing microorganisms. Ideally, acorns should be collected from the ground only after they have been allowed to dry. This allows the acorns to better resist heat and drying and lessens the likelihood that they will be infected with soil-borne pathogens while on the ground.
Likewise, it is important to select healthy looking acorns that are free of internal damage. Acorns infested with weevil grub or filbertworm larvae should be discarded because the larvae will bore out of the acorn and cause internal damage when it is eaten by animals.