The apple tree comes in many varieties, from the cultivated apple trees that produce one of the most important crops grown in temperate American climates to the many types of wild apple trees. These wild apples, all members of the rose family--as are their cultivated cousins--include species such as the Southern crab apple, Biltmore crab apple, Oregon crab apple and the sweet crab apple. The leaves of an apple tree can aid someone in the field with the identification of the particular tree if he or she has keen powers of observation.
All apple trees have leaves that share three features. Apple trees, cultivated or wild, are deciduous, meaning the leaves fall off before winter and then grow back in the spring. The leaves of apple trees grow in an alternate fashion on the twigs of the branches. And the edges of apple tree leaves possess teeth, seen as obvious serrations along the sides of the leaf.
The color of the domestic apple leaf is usually a dark shade of green on its upper surface, with the lower surface having a much duller, almost whitish shade to it. The Southern crab apple has nowhere near as deep a green color to it, with the upper part of the leaf a very dull green and the bottom part even paler. Sweet crab apple leaves are yellow-green above and duller underneath. Prairie crab apples have a shiny green leaf that has a more subtle hue of green underneath.
While apple trees have simple leaves, or leaves that have just one solitary blade, there are differences between species in their shape. Many of the cultivated apple trees have oval leaves. The differences are much greater between the apples such as the Biltmore crab apple, a tree that has almost triangular leaves, much like some birches. The Southern crab apple has earned the nickname "narrow-leaf crabapple" because of the oblong shape to its leaves.
No apple trees possess what a botanist would consider a long leaf, but some types have leaves greater in length than others. According to the" National Audubon Society Field Guide to Trees," the sweet crab apple may have leaves as long as 4 inches while the Southern crab apple rarely has a leaf 3 inches long. This tree has leaves of a much smaller width, with most between a half-inch and three-quarters of an inch wide. In comparison, most other apple trees, including cultivated types, are at least twice as wide.
Most kinds of apple trees have at least one side that is hairy, especially when the tree is in the process of maturing. The bottoms of many cultivated apples have a fine coating of hair and both sides of crab apples have this feature as well. In addition, the stems of the leaves are hairy.