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Swamp White Oak

Swamp White Oak (Quercus bicolor), primarily an Oak of the Midwestern United States, is found throughout most of Ohio, although it is not abundant in the southeastern Appalachian counties. It is a frequent inhabitant of wet woods, swamps, wetlands, bottomlands, and near bodies of water, although it is very drought tolerant and can be planted in soils that are dry in summer.

Of all the members of the White Oak group, the undersides of its leaves are the most white, and when contrasted with its dark green leaf uppersides in the breeze, the specific epithet "bicolor" is appropriate.

Its wood is indistinguishable from White Oak when cut and is used for the same purposes. Its canopy is often ascending in youth and middle age, becoming more rounded at maturity. Swamp White Oak may reach 70 feet tall by 60 feet wide at maturity, when found in the open. As a member of the White Oak group and the Beech Family, it is related to the Beeches, Chestnuts, and other Oaks.

Planting Requirements

Swamp White Oak prefers rich, deep, moist to wet, poorly-drained, acidic soils, but adapts well to dry and average soils that are neutral to slightly alkaline in pH. Along with Pin Oak and Swamp Chestnut Oak, it is one of the best hardwoods for wet soils, but it adapts better than many Pin Oaks to wet soils that also have a neutral to slightly alkaline pH. It thrives in full sun to partial sun (but is shade tolerant in youth) and is found in zones 4 to 8.

Potential Problems

Swamp White Oak has three notable problems that may occur. Along with English Oak, it is the Oak most likely to get powdery mildew on its foliage in late summer and early autumn. This causes no damage to the tree; it just makes the leaves have a white cast on a green background.

Along with Bur Oak, Swamp White Oak may have rounded galls on its twigs and branchlets, the result of chewing by the Oak rough bulletgall wasp. Unless infestations are especially dense, no long-term damage is done. Finally, this species will develop chlorosis in high pH (very alkaline) soils, almost always the result of being transplanted into chalky and gravelly urban soils, usually near asphalt and/or concrete.

Identifying Features

Leaf
Swamp White Oak has leaves that are alternate, obovate, with deeply crenate margins and undersides that are distinctly white. Leaf shape is somewhat variable in Swamp White Oak in terms of how shallow or deep the spaces are between the crenations or lobes on the margin.

Along with English Oak, this species is the most likely to develop powdery mildew on its leaves by late summer. Along with White Oak, Swamp White Oak has the best autumn color of the various members of the White Oak group, usually with crimson shades of fall color.

Flower/Fruit
Swamp White Oak is monoecious, having pollen-bearing catkins in mid-spring that fertilize the inconspicuous female flowers on the same tree. Since it is a member of the White Oak group, the fruits (acorns) only take a single season to develop.

Swamp White Oak along with Swamp Chestnut Oak, Chestnut Oak, and English Oak, is known for the long peduncles that attach to its acorns although Swamp White Oak has the thickest peduncles of the four mentioned. Its acorns ripen in early to mid-autumn.

Twig
The terminal buds of Swamp White Oak are often very small.

Although its twigs are not usually corky, its branchlets are often very flaky, and the branches develop distinct (but not unique) flares of bark, especially on the undersides of the horizontal branches as in White Oak.

Bark
Mature bark becomes ridged and furrowed, but retains the light gray color that is characteristic of the White Oak group.

The growth habit of Swamp White Oak is perhaps the most stately and uniform of the White Oak group, being densely oval, upright, and symmetrical through middle age, then becoming more spreading with advanced maturity.