Water Oak

Quercus nigra L.

Description

Water oak is a member of the beech family (Fagaceae) and is a deciduous tree with a spreading, rounded open canopy that can spread 60-70 feet wide ¹.  It can reach between 60 to 80 feet in height with a drink ¹. The trunk is reddish-brown color, is brown and smooth when the tree is young, and changes to a gray-black color as it matures ¹.  While a fast growing tree, it may live only 30 to 50 years ¹².  Leaves are entire with three shallow lobes and small, sometimes indistinct, bristles ¹.  Leaf blades are 2-4 inches in length, with a green and shiny upper surface and paler green lower surface ¹.  In the fall, the leaves change to a yellow color ¹. Its unisexual flowers occur on the same tree in the spring with a yellow-brown male catkins and indistinct female flowers.  Its brown acorns  take 2 years to mature ⁵.  Acorns are one-half inch with a cap covering 1/3 or less of its length ¹.

Mature trunk of water oak.  B. Hubick, Maryland Biodiversity Project ⁶

Leaves of water oak.  K. Schultz, Maryland Biodiversity Project⁶

Male flowers in catkins of water oak. J. Brighton, Maryland Biodiversity Project ⁶

Acorns of water oak.  J. Brighton, Maryland Biodiversity Project ⁶

Distribution

This tree is found along the Coastal Plain in the southeastern United States from New Jersey to northern Florida and east to Texas Oklahoma and Arkansas ⁴.  In Maryland these trees can typically be found in the lower Eastern Shore⁶. They can survive in an urban environment, and are often seen as highway medians or on streets where there are no sidewalks ¹.  They are sensitive to sulfur dioxide pollution ⁴. 

Natural range of water oak ¹⁰

Wildlife Importance

The acorns produced by the water oak serve as a good food source for wildlife ¹.  Many animals such as raccoon, mice, wild turkey, and white-tailed deer all eat its acorns ².  Water oak can also provide a habitat for smaller cavity-nesting animals such as red-bellied woodpeckers and squirrels ⁴. Water oak is a larval host for a variety of butterflies and moths, including Horace’s Duskywing, White M Hairstreak, and Northern Hairstreak ¹¹.

Economic Importance

Timber, fuel, and a plywood for fruits and vegetable containers are some of the ways that water oak can be used for economic gain ³. Water oak can also be used to treat ailments such as diarrhea, eczema or canker sores ⁸.  The root system of the water oak can also stabilize the soil to prevent erosion ⁹. This is economically beneficial, because erosion has a negative impact on farm production ⁹.  

Threats

Water oak is a very sensitive tree, that is vulnerable to illness, and pests ⁴. Their numbers have unfortunately been declining due to negative human interactions ².  This includes actions like row-cropping or extensive clearing ².  Water oak does not compete well with other species for nutrients needed to grow ³.  It is also easily injured by fire and susceptible to butt rot ³.

Interesting Facts

• Water oak is susceptible to air pollution ⁴. This is especially tricky since these plants are found in high human traffic areas with a lot of air pollution. 
• If a water oak seedling does not get adequate sunlight it grows 1.9 inches a year ⁴.  This is atypical, as they can grow 24 inches or more a year– even under unfavorable conditions ⁴. 
• Water oak can also be referred to as “pin oak” in Texas because it shares many similarities with  true pin oak (Quercus palustris) ⁵. Only the leave shape of both species differ ⁵.
• The Water oak was often used by native Americans for food and medicine ¹².
• The fruits and leaves are slightly poisonous to humans until the tannins are leached or boiled out ¹².

References

1. University of Florida Extension: Quercus nigra
2. Missouri Department of Conservation: Water oak
3. USDA Forest Service Silvics, Vol. 2, hardwoods: Quercus nigra
4. USDA Forest Service Fire Effects Information System: Quercus nigra
5. Trees of Texas: Water oak
6. Maryland Biodiversity Project:  Water oak
7. Flora of North America:  Quercus nigra
8. Peace Health:  Oak
9. Washington State University Extension, Shore Stewards:  Using plants & trees for stability
10. Wikipedia: Quercus nigra
11. Lady Bird Johnson Wildflower Center: Quercus nigra
12. North Carolina State Extension: Quercus nigra

 

Contributed byT. Rhamdeow and L.  Vanderbeek 

Towson University Glen Arboretum