Slippery elm is a medium-sized tree with a long trunk dividing into large branches that form a spreading, open, flat-topped crown.
Leaves are alternate, simple, 4–8 inches long, broadest near the middle; margin with smaller teeth along the lower side of the larger teeth; tip with a long, narrow point; base uneven. Upper surface dark green, very rough, with stiff hairs; lower surface paler, with soft hairs.
Bark is reddish-brown to gray, grooves shallow, ridges long, flattened; inner bark with a sticky sap, slippery when chewed.
Twigs are stout, gray, densely hairy, rough; smooth with age; inner surface slippery when chewed; buds dark purplish- to reddish-brown, hairy.
Flowers February–April, before the leaves, in dense clusters on short stalks; flower about ¼ inch long, green, hairy, petals absent.
Fruits April–June, in clusters; fruit ¼–¾ inch long, seed surrounded by a papery wing; wing reddish-brown, broadest in the middle, notched at the top, smooth; seed solitary, flattened.