Oaks Quercus nigra

Water oak is native medium sized fast growing deciduous tree; however, sometimes it is considered an evergreen in the deep south. It is a member of the red oak group. It usually grows to a height of 50 to 80 feet tall and 50 to 70 feet wide. It has a conical to broad, rounded habit with a trunk diameter of 3.5 feet. The water oak is regarded as weaker wooded in comparison to most oaks, and it also has a shorter life span. It may only live 30 to 50 years. It is a member of the Fagaceae or beech family.

The water oak is native to the central and eastern United States.  It is found in forests, flood plains, and along rivers and streams or in sloped areas with drier soils. It is commonly found in the Coastal Plains and Piedmont areas of North Carolina in bottomland forests.

This tree prefers rich, medium to wet acidic soils in full sun. It is adaptable to other soil types and part shade. The water oak transplants easily and adapts well to wet sites. 

The leaves of the water oak are bluish green, spatulate, or variable in shape and may have 0 to 5 lobes. The margins may be entire, or bristle tipped. The male flowers are cylindrical catkins, and the female flowers are short spikes. The fruit is an acorn that has a cup with wooly scales. It requires two growing seasons for the acorns to reach maturity.

The water oak is a risk for breakage from wind or ice. Other oaks such as the red oak, white oak, and swamp white oak have stronger branch structure and should be considered as an alternative. The water oak is similar to the willow oak in tree form and bark description, but the leaves are distinctly different.

The water oak is a great tree for naturalized areas, street tree or shade tree in large areas. It is particularly useful for low spots or moist areas in the landscape.

It is a host plant for the larvae of the Imperial moth (Eacles imperialis), as well as numerous butterflies, including Banded hairstreak (Satyrium calanus), Edward's hairstreak (Satyrium edwardsii), Gray hairstreak (Strymon melinus), White-m hairstreak (Parrhasius malbum), Horace's duskywing (Erynnis horatius), and Juvenalis duskywing (Erynnis juvenalis).

Seasons of Interest:

Bark:  Winter    Foliage:  Summer and Fall       Fruits: Fall

Quick ID Hints:

• brown and smooth bark when the tree is young, gray black, furrowed, and rough with age
• stems are slender, thin, and reddish-brown.
• leaves are bluish- green on surface, paler beneath, spatulate, lanceolate, or variable in shape and may have 0 to 5 lobes.
• alternate leaves with smooth or bristle-tipped margins
• male flowers are drooping catkins, and female flowers appear as short spikes
• fruit is an 1/2 to 1-inch nearly black acorn with a flat, scaled cap that covers about 1/3 of the nut.

Insects, Diseases and Other Plant Problems:  Oaks are susceptible to many diseases. The water oak is susceptible to oak wilt, often with fatal consequences. Other less serious diseases include chestnut blight, shoestring root rot, anthracnose, oak leaf blister, cankers, leaf spots, and powdery mildew. Scale, oak skeletonizer, leaf miners, galls, oak lace bugs, borers, caterpillars and nut weevils are potential insect pests. Chlorosis can occur if the pH level is too high and results in iron deficiency. Limbs are notoriously weak and at risk for breakage particularly in high winds or during winter snow and ice storms. 

VIDEO created by Andy Pulte for “Landscape Plant Identification, Taxonomy and Morphology” a plant identification course offered by the Department of Plant Sciences, University of Tennessee.