The rock elm, or cork elm, is the most important lumber tree of the elms. It is smaller than the American elm and has a straight trunk and oblong crown.
Leaves are shiny dark green above and light green below.
The larger twigs have corky, irregular, prominent ridges. The brown buds are broadly rounded and velvety. The characteristiccorky ridges are present on the small trunks and branches and on largertrunks the bark is broken into narrow, interlacing ridges. The waferlike fruit is winged, contains one seed and is similar to the fruit of other elms but is narrower and velvety.