Flower:

Male and female flowers are borne separately on the same branch, the males on 1 to 3-inch long green, string-like clusters (called catkins) from bud clusters in the axils at the ends of the previous season's growth. Female flowers are green and indistinct, on a stout 1 to 1½ inch stalk; 1 to 3 sit in the leaf axils of new growth.

Leaves and bark:

Leaves are simple and alternate, broadly spatula shaped, 4 to 8 inches long and 2¾ to 4¼ inches wide, widest just above the middle, the tip end tapering in a series of shallow, rounded or bluntly pointed lobes, the lower end with 1-2 shorter rounded lobes, rapidly tapered to a V shaped base, on a short stalk. Upper surface is deep green with a glossy to dull sheen, the lower light green to grayish, densely hairy with mix of fine appressed hairs and scattered clusters of long hairs. While not noted for its fall foliage, some specimens can display an impressive mix of scarlet, gold and green that fade fairly quickly to a monotone light brown, typically shed before the onset of winter.

The trunk can be over 3 feet in diameter at breast height (dbh). In its natural forest setting, its spreading branches form a large, high crown in the canopy. In more open urban parks and residential areas, the crown can be strongly globe shaped. The bark is gray to brownish, medium to coarse textured, with flattened, plate-like to corky ridges with medium to deep vertical furrows. Younger trees often exhibit a loose, scaly, almost birch-like bark on the trunk that persists into the branches on mature trees, but is nearly smooth on the branches. Twigs are reddish brown to gray, and smooth.

Fruit:

Fruit is a round egg shaped to elliptical nut (acorn), 2/3 to almost 1 inch long with a dome-like cap over the end, covered with coarsely fringed tipped scales, 1 to 3 acorns on a stalk up to 2 inches long. The cap is about 1/3 the total length of the fruit.

Notes:

In Minnesota, the wild Swamp White Oak is a Special Concern species due to the destruction of its natural habitat in the flood plain of the lower Mississippi, by dams built for river navigation at the turn of the last century. The species itself however, is in no danger of extinction, as it has been widely adopted by the landscape industry that has spread it throughout urban landscapes statewide where it preforms quite nicely as a boulevard/park tree. At first glance it might be confused with Bur Oak (Quercus macrocarpa), but Swamp White Oak's leaves are more uniformly lobed and missing the deeper sinuses common in Bur Oak. Notice also the long, stiff stalk on its acorns where Bur's are attached directly to the twig. In winter dormancy, the bark on Swamp White branches have loose, plate-like scales compared to Bur's cork-like ridges that often extend out to the twigs.