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bur oak

bur oak (Quercus macrocarpa)
Photo © Illinois Department of Natural Resources

Features and Behaviors

The deciduous bur oak tree may grow to 120 feet tall with a trunk diameter of five feet. Its bark is dark brown or yellow-brown with deep furrows. The bud is rounded or slightly pointed at the tip, yellow-brown to red-brown and hairy. The simple leaves are arranged alternately along the stem. The leaf blade is broad at the upper end and coarsely round-toothed. The leaf has five to seven lobes. Each leaf is dark green and smooth or slightly hairy on the upper surface and pale and hairy on the lower surface. The leaf may be 14 inches long and seven inches wide with a one inch leaf stalk. Male and female flowers are separate but located on the same tree. Neither type of flower has petals. Male (staminate) flowers are arranged in drooping catkins, while the female (pistillate) flowers are clustered in a small group. The fruit is a solitary acorn. The dark brown acorn may be ovoid to ellipsoid and up to one and three-quarter inches long. The hairy cup covers half to nearly all of the nut and has a fringe of long scales.

The bur oak may be found statewide in Illinois. This tree grows almost anywhere, from dry ridges to bottomland woods. The bur oak flowers in April and May, about the time that its leaves begin to unfold. Its heavy, hard wood is used in making cabinets, for ship building, for fence posts and for fuel.

Illinois Range


​Kingdom: Plantae

Division: Magnoliophyta

Class: Magnolioposida

Order: Fagales

Family: Fagaceae

Illinois Status

​common, native

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