Culture
Best grown in rich, humusy, acidic, medium to wet soils in full sun. May not be reliably winter hardy throughout the St. Louis area.
Noteworthy Characteristics
Quercus nigra, commonly called Water oak or possum oak, is a medium sized deciduous (sometimes semi-evergreen in southern areas) oak of the red oak group that typically grows in a conical form to 50-80’ tall with a broad rounded crown. Trunk diameter extends to 3.5’. Brownish gray bark becomes grayish black with age with rough scaly ridging. Water oak is native primarily from New Jersey to Florida and Texas, extending northward along the Mississippi River valley to western Kentucky, southern Illinois and the Missouri bootheel. It is typically found in low woodland areas, floodplains and along streams and rivers. Insignificant monoecious flowers in separate male and female catkins appear in spring. Fruits are broad-rounded acorns (to 1/2” long) in short-stalked cups with woolly scales. Acorns are a source of food for wildlife. Narrow, smooth-margined, spatula-shaped, oblong leaves (2-4” long and 1-2” wide) are three-lobed to entire at the tips. Leaves are dull bluish-green above and paler with pubescence beneath. Old leaves tend to drop in late fall to early winter, but may persist on the tree throughout most of the winter in the southern parts of the growing range (particularly within USDA Zones 8-9).
Genus name comes from the classical Latin name for oak trees.
Specific epithet means black.
Problems
Water oak is a weak-wooded tree that is susceptible to trunk cankers and rots, all of which makes in vulnerable to limb breakage from wind and winter snow/ice. Oaks in general are susceptible to a large number of diseases, including oak wilt, chestnut blight, shoestring root rot, anthracnose, oak leaf blister, cankers, leaf spots and powdery mildew. Potential insect pests include scale, oak skeletonizer, leaf miner, galls, oak lace bugs, borers, caterpillars and nut weevils.
Uses
A medium oak for moist areas or lowspots. Has been used as a street tree and shade tree, particularly in southern towns and cities.