The American elm is a majestic tree, native to the eastern United States from the Gulf Coast to southern portions of Canada. The various species of ash that grow in the United States occur in different parts of the country. Elm is a stately shade tree, while the wood of ash is of such hardness that for decades manufacturers have used it to produce such things as baseball bats and furniture. Someone with little knowledge of these two types of trees can identify them by carefully observing the trees and looking for some of the characteristics that separate them from other species.
Consider the leaves of both the elm and ash. Elm leaves are elliptical in shape and 4 to 6 inches long, possessing double-toothed margins. These leaves have distinct veins that radiate from the middle of the leaf in both directions. Elm leaves are green but turn chartreuse or golden in the autumn. The leaves of an ash tree are compound leaves, meaning multiple small leaflets grow off a central rachis—a long twiglike extension. Ash leaves will have an odd number of leaflets in most species, with the white ash for example typically having seven; two opposite each other along the rachis and one leaf at the very end. Ash leaves change from green in the warm months to yellow in the fall, with some changing to purple and red.
Estimate the size of these trees. White ash can achieve a height of up to 70 feet and has a rounded crown 50 feet in width. American elm has a shape like a vase, spreading outwards as it grows. Elms are subject to Dutch elm disease, a fungus spread by a specific type of beetle that prevents many from ever growing to their mature heights of 80 feet. Most elms begin to feel the effects of this ailment at 40 feet tall.
Identify these two trees by their unique fruits. The flowers of an elm tree eventually develop into a fruit botanists call a samara. In the case of the elm, the samara is oval, flattened, about half an inch long and enclosed in a papery case with a distinct notch at the end. The ash trees also have samaras, but theirs differ greatly from the elms. Only the female ash trees have a samara, hanging in clusters where the flowers once grew. The samara consists of a seed on one end that looks as if it sprouted a single wing. These seeds will fall off the tree in autumn, helicoptering down to the ground because of their shape.