Flower:

Male and female flowers are borne separately on the same branch, the males on 1½ to 3-inch long green, string-like clusters (called catkins) from bud clusters at the tip of the previous season's growth. The female flowers are nestled in the leaf axils of fresh growth, with 1 to 3 green flowers on a short, stubby green stalk.

Leaves and bark:

Leaves are simple and alternate, broadly club shaped (obovate) in outline, 3½ to 7 inches long and 2 to 6 inches wide, with 3 to 5 dominant rounded finger-like lobes evenly distributed on each side, sometimes with a few smaller lobes towards the base, the leaf's lower half tapered to a short stalk. The upper surface is darker green than the underside, both are hairless and often glossy to shiny. Leaves turn dark red in fall

The trunk can be over 36 inches in diameter at breast height (dbh). In closed canopy forests it is tall and straight with few or no lower branches but in more open areas, lower branch formation can create a crown that is wider than tall. The bark is gray, medium to coarse textured with flattened, plate like vertical ridges but becomes thinner with scaley sheets on the branches. Twigs are gray to reddish with scattered white, lens-shaped pores (lenticels).

Fruit:

Fruit is a round to egg shaped nut (acorn), ½ to just under 1 inch long, usually longer than wide, set in a dome-like cup that is rough and warty but generally free of hair-like fringes, on a stalk up to about 1 inch long. The nut is about 3 times longer than the cap.

Notes:

White Oak is an eastern forest species restricted to east central and southeastern Minnesota. Similar in size and shape to Bur Oak (Quercus macrocarpa) it is easily distinguished by its more plate-like bark on the branches, more evenly lobed leaves and fringeless acorn caps. Its thinner bark has not allowed it to survive in fire dependent ecosystems and has prevented its migration into western prairie habitats as Bur Oak has. Like Bur Oak it is extremely long lived, to over four centuries. Bur and White Oak hybrids are called Bebb's Oak (Quercus x bebbiana) but they are not a common occurrence.