Look at the leaves of the chestnut tree you are identifying. American chestnut tree leaves are large, and the body of the leaf is a long, thin oval. The Chinese chestnut tree's leaf is smaller and more circular. The “teeth,” or grooves of the leaves, on the American chestnut tree are deeper than its Chinese counterpart and slightly curved. The Chinese chestnut tree does not have curved teeth.
Look at the underside of the leaf. Chinese chestnut tree leaves have a fuzzy underside, while the American chestnut tree's leaf is mostly smooth on the bottom, with a few hairs along the middle seam of the underside of the leaf.
Look at the twigs of the tree. American chestnut trees have smooth, small twigs. Chinese chestnut trees have large, hairy twigs.
Look at the trunk of the tree. The trunk of American chestnut trees is slim and very straight. The Chinese chestnut has a larger trunk that may taper or curve.