Ash trees (Fraxinus spp.), both native and European species, are common landscape trees throughout the United States. American chestnuts (Castanea dentata) are almost extinct in their native habitat because of chestnut blight, but Asian, European and hybrid types have been widely planted. Examine the branching pattern, fruit, leaves and bark to determine whether a tree is an ash or chestnut.
Leaves, branches and buds on an ash tree are directly opposite each other. Branches sometimes die, so not every branch will have an opposite partner, but the general pattern is opposite. Chestnut leaves and branches are alternate. The leaves are staggered along the twigs and branches staggered along the trunk. These branching patterns are the same for all members of the two species.
Chestnut trees produce two to three hard, shiny nuts in a spiky husk. These nuts ripen and fall to the ground in autumn. They are edible when they are cooked and are often associated with Christmas. Ash trees produce samaras, or winged seeds. These look like a little oar and hang in clusters on the tree until late fall or early winter. They are not edible. Some ash species have male flowers on one tree and female flowers on another. Male trees will not produce seeds.
The leaf of a tree starts at the bud. Ash leaves are pinately compound, meaning that one leaf has many leaflets and looks a little like a feather. Each leaf has 5 to 11 leaflets. The leaflets are opposite each other on the petiole and may be finely toothed or smooth along the edge. Chestnut leaves are lance- shaped and toothed. American chestnut leaves have large, hooked teeth. Other chestnuts have smaller teeth but none have smooth-edged leaves.
Bark is smooth with many lenticils, or pores, on both young ash and young chestnut trees, although it is darker on chestnut trees. Older ash trees develop bark with tight ridges in a diamond pattern. Chestnuts that survive to an older age develop loose, coarse bark with deep fissures and flat, shiny ridges. Use bark characteristics for identification only in combination with other characteristics.