A picturesque oak with stout, rugged branches, the bur oak grows to 80 feet tall or more and has a broad, spreading, rounded crown. Leaves are dark, lustrous green above and gray or whitish and hairy below. Fall color is a dull yellow-brown. Male and female flowers are produced in separate catkins on the current year's growth.
Male catkins are yellowish, slender and hanging.
Female catkins occur in reddish clusters on a short stalk. The broadly ovoid acorns are 0.8 to 2 inches long with the cup covering one-half or more of the nut. A distinctive fringe of long, soft bristles protrudes from the rim of the cup and the tip of the nut has a short beak. The reddish-brown, imbricate buds are conical to broadly ovate and are densely covered with fine, gray hairs. Bark is thick, dark gray-brown and separated into irregular, scaly ridges.