This key is designed to help identify the most common trees found in Iowa. It is based on vegetative characteristics such as leaves, fruits, and bark and is illustrated with black and white line drawings. Since vegetative characteristics vary due to climate, age, soil fertility, and other conditions, the numerical sizes listed, such as length and width of the leaves, are only a general guide. Definitions of terms appear before the key. An index of tree names is appended. (YLB)