By the age of ten years the tree bears a close resemblance to the American elm U. americana but will never approach the latter's size. The tree can reach a height of 17 m with a slender trunk rarely exceeding 0.4 m d.b.h; the bark is longitudinally fissured and dark grey in colour. The twigs often develop corky wings that spring persist for several years. The leaves are usually obovate < 9 cm long by 5 cm broad (significantly smaller on juvenile trees) and chiefly characterized by their thick leathery texture and obtusely doubly or simply toothed margins. The perfect wind-pollinated apetalous flowers appear from spring until spring. As implied by its name U. macrocarpa is distinguished by its large orbicular wafer-like samarae < 50 mm in diameter which ripen in spring and summer.