J. A. Vozzo
Water oak (Quercus nigra), sometimes called possum oak or spotted oak, is commonly found along southeastern watercourses and lowlands on silty clay and loamy soils. This medium-sized rapid-growing tree is often abundant as second growth on cutover lands. It is also planted widely as a street and shade tree in southern communities.
Quercus nigra L.
Wet pine savannas (SPS-RF, WLPS, VWLPS).
Occasional. Apr; Sep–Nov (of second year). Thornhill 203, 207, 282, 362 (NCSC). Specimens seen in the vicinity: Sandy Run [Neck]: Wilbur 55257 (DUKE!); Sandy Run [Patterson]: Taggart SARU 212 (WNC!). [= RAB, FNA, Weakley]
Regularity: Regularly occurring
Jersey and Delaware to southern Florida and west to eastern Texas. It
occurs north along the Mississippi Valley to southeastern Oklahoma,
Arkansas, Missouri, and southwestern Tennessee .
Occurrence in North America
OK SC TN TX VA
-The native range of water oak.
Water oak is a medium-sized tree with glabrous twigs, membranous leaves,
and a straight, slender trunk. On a good site, water oak can reach 105
feet (32 m) in height and attain 6.5 feet (2 m) in d.b.h. It is
semievergreen in warmer parts of its range but completely deciduous in
other areas [10,43]. Water oak has a shallow, spreading rooting habit
Water oak grows on levees, high ridges, and elevated margins of swamps,
rivers, and hydric hammocks which flood deeply and frequently but drain
rapidly because of relief [6,12,20,37,49]. Water oak will also grow on
uplands to about 1,000 feet (300 m) in elevation where soils remain
moist . Water oak grows well on better drained silty clay or loamy
soils and poorly on poorly drained clay soils. It grows primarily on
Water oak is weakly to moderately tolerant of seasonal flooding. It can
survive up to several months of flooded soil, but mortality is high if
this is a yearly occurrence. Generally, water oak is tolerant of
several weeks of flooding each growing season [3,7].
In addition to overstory associates mentioned in SAF cover types, common
associates of water oak include Nuttall oak (Quercus nuttallii), white
oak (Q. alba), American beech (Fagus grandifolia), pecan (Carya
illinoensis), winged elm (Ulmus alata), blackgum (Nyssa sylvatica),
white ash (Fraxinus americana), yellow-poplar (Liriodendron tulipifera),
southern magnolia (Magnolia grandiflora), flowering dogwood (Cornus
florida), rough-leaf dogwood (C. drummondii), honeylocust (Gleditsia
triacanthos), Carolina laurelcherry (Prunus caroliniana), hawthorn
(Crataegus spp.), American hornbeam (Carpinus caroliniana), swamp privet
(Forestiera acuminata), spruce pine (Pinus glabra) .
Key Plant Community Associations
Water oak occurs primarily in bottomland forests. The following
published classifications list water oak as a dominant species:
The natural communities of South Carolina 
Forest vegetation of the lower Alabama Piedmont 
Eastern deciduous forest 
Forest associations in the uplands of the lower Gulf Coastal Plain 
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the terms: hardwood, swamp
70 Longleaf pine
74 Cabbage palmetto
80 Loblolly pine - shortleaf pine
81 Loblolly pine
82 Loblolly pine - hardwood
83 Longleaf pine - slash pine
84 Slash pine
85 Slash pine - hardwood
88 Willow oak - water oak - diamondleaf oak
89 Live oak
91 Swamp chestnut oak - cherrybark oak
92 Sweetgum - willow oak
93 Sugarberry - American elm - green ash
94 Sycamore - sweetgum - American elm
104 Sweetbay - swamp tupelo - redbay
111 South Florida slash pine
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES12 Longleaf - slash pine
FRES13 Loblolly - shortleaf pine
FRES14 Oak - pine
FRES16 Oak - gum - cypress
FRES17 Elm - ash - cottonwood
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K098 Northern floodplain forest
K111 Oak - hickory - pine forest
K112 Southern mixed forest
K113 Southern floodplain forest
Soils and Topography
Associated Forest Cover
Water oak is classified as a bottom-land forest cover type Willow Oak-Water Oak-Diarnondleaf Oak (Society of American Foresters Type 88) (6). It is also an associated species in Live Oak (Type 89) and Sweetbay-Swamp Tupelo-Redbay (Type 104).
Diseases and Parasites
Fire Management Considerations
Hardwoods growing within a pine forest are often controlled with
prescribed fire. Water oaks up to 3 inches (7.6 cm) in d.b.h. are
top-killed and sprouts kept small and controllable with prescribed
winter fires. Summer fires are also effective but are more detrimental
to the wildlife food supply . Herbicides combined with fire can be
used to eradicate larger water oaks .
Because water oak leaves and habitat are often moist, fuels should be
allowed to dry at least 3 weeks following a rain of 0.5 inch (1.3 cm) or
more. Some fires will not carry even under ideal conditions of less
than 4 percent fuel moisture, 20 to 30 percent relative humidity, and 2
miles (3.2 km) per hour winds within the stand .
Burning has only a slight effect on the quality of water oak browse. In
one study, protein was slightly higher and phosphoric acid slightly
lower on burned plots than on unburned plots .
Plant Response to Fire
Water oak, including seedlings, sprout from the root collar if
top-killed by fire. Larger water oaks that survive fire but have fire
scars are extremely susceptible to butt and heart rot . After being
fire scarred, the average rate of spread of rot in water oak is 1.25
feet (0.4 m) per decade .
Immediate Effect of Fire
Water oak is easily damaged by fire . Low-severity surface fires
top-kill water oak less than 3 to 4 inches (7.6-10.2 cm) in d.b.h. The
bark of larger trees is thick enough to protect the cambium from
low-severity fires and the buds are above the heat of the fire. In a
study on the Santee Experimental Forest in South Carolina, periodic
winter and summer low-severity fires and annual winter low-severity
fires were effective at reducing the number of hardwood stems (including
water oak) between 1 and 5 inches (2.6-12.5 cm) in d.b.h. Annual summer
fires also reduced the number of stems in that size class, as well as
nearly eliminating all stems less than 1 inch (2.5 cm) in d.b.h. Root
systems were weakened and eventually killed by burning during the
growing season .
The mean time in seconds for water oak cambium to reach the lethal
temperature of 140 degrees Fahrenheit (60 deg C) when a standardized
flame was applied to living bark was 30.2 seconds for 0.2 inch-thick
(0.5 cm) bark, 61 seconds for 0.3 inch-thick (0.8 cm) bark, and 136
seconds for 0.4 inch-thick (1 cm) bark .
Water oak has relatively thin bark compared to other oaks  and is
easily top-killed by even light fire. It survives fire by sprouting
from the root crown . Water oak's moist habitat and proximity to
water discourages fire entry. Water oak leaves and other fuel along
waterways are often moist and difficult to burn . Water oak is
excluded from upslope forests by periodic summer burning .
Based on flame applied directly to living bark, water oak is less
resistant to fire than pine, southern magnolia, and sweet bay; of
more-or-less equal resistance as red maple (Acer rubrum), flowering
dogwood, water tupelo (Nyssa aquatica), and river birch (Betula nigra);
and more resistant than sweetgum, American holly (Ilex opaca), and black
cherry (Prunus serotina) .
More info for the terms: climax, hardwood
Facultative Seral Species
Water oak is intolerant to semi-intolerant of shade [19,34,50]. It
germinates in shade but requires moderate light for development.
Because of slow early growth, water oak does not compete well .
Water oak is a frequent early hardwood invader . In the absence of
fire, it invades and eventually succeeds pine forests . On
fine-textured loess soils that retain moisture, water oak will colonize
old abandoned fields if a seed source is nearby . As a hardwood
forest matures, water oak will stabilize or decline in abundance .
Water oak is generally considered a subclimax or transitional species
[19,32,50]. Because of its weak to moderate tolerance of seasonal
flooding, however, water oak may form a topographic climax on ridges
elevated less than 5 feet (1.5 m) above floodplains [13,32,34].
Seed production and dissemination: Water oak is monoecious. It bears
seed by age 20, and production is good on alternate years. The heavy
acorns are disseminated by gravity, water, and animals  such as blue
jays and ground squirrels, which cache acorns in the soil [8,21,44].
Germination and seedling development: Seed viability is high.
Germination is hypogeal and occurs in the spring following maturation.
Because of a generally late spring emergence, seedling mortality from
flooding is low. The seedlings do not tolerate prolonged submergence.
Because of the large seed, young seedlings have high initial
survivorship regardless of available light, drought stress, or
herbivory. Seedlings require abundant moisture for the entire growing
Under favorable conditions, water oak may grow 24 inches (60 cm) a
year . Water oak seedlings suppressed by shade, however, grew only
1.9 inches (4.7 cm) per year in a study along the Neches River in east
Texas . A suppressed individual will grow epicormic branches 
Vegetative reproduction: If top-killed, water oak of all ages will
sprout fairly efficiently from the root crown [38,45,50].
Growth Form (according to Raunkiær Life-form classification)
Reaction to Competition
Water oak is easily injured by fire and even a light burn kills stems of seedlings. Survivors are extremely susceptible to butt rot.
Life History and Behavior
Water oak staminate and pistillate flowers develop shortly before or at
the same time as new leaves. Acorns mature in September of the second
year and are dispersed from September through November [3,50].
Seedlings require abundant moisture the entire growing season but do not tolerate prolonged submersion. Under optimum conditions water oak grows at a rate of 60 cm (24 in) per year for the first 25 years (7).
Seed Production and Dissemination
Flowering and Fruiting
Flowers are easily killed by late frosts after leaf buds open. The trees then defoliate and develop new leaves but do not generate a second crop of flowers.
Growth and Yield
Molecular Biology and Genetics
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
on impervious or dry terrace soils . Trunk borers (Enaphalodes spp.
and Prionoxystus spp.) and leaf hoppers (Erythroneura spp.) attack water
oak along with root rot (Ganoderma curtisiicone) and cone rusts
(Cronartium spp.). Although not seriously harmed itself, water oak is
an extremely susceptible host to the alternate stage of fusiform rust
(Cronartium quercuum f. sp. fusiforme), a serious disease of southern
pines . Trunk canker and heart rot are caused by a variety of
organisms. Water oak is also parasitized by mistletoe (Phoradendron
Water oak is highly susceptible to air pollution, especially sulfur
dioxide. Flowers are easily killed by late frosts .
Water oak has great potential for fiber production on sites to which it
is specifically adapted. Pine does poorly on many of these sites and
could be replaced with water oak . Clearcutting followed by
planting or direct seeding is the best method to establish hardwood
forests . Competing vegetation and destruction of acorns by
squirrels and chipmunks are the biggest problems associated with direct
seeding. Moisture is a major limiting factor for water oak regeneration
. Collection, storage, stratification, and viability testing of
water oak acorns are detailed .
Nutria uproot and eat seedlings. Translucent plastic tubes placed
around newly planted seedlings were effective in protecting seedlings
from nutria in Louisiana .
Herbicides such as 2,4,5-T, picloram, and glyphosate can be used to
control water oak in pine plantations [31,50].
Relevance to Humans and Ecosystems
Other uses and values
Value for rehabilitation of disturbed sites
Water oak is frequently used to restore bottomland hardwood forests in
the Southeast on land that was previously cleared for agriculture or
pine plantations. Both direct seeding and planting methods work well
Water oak performed well when planted on fill slopes in Decatur County,
Tennessee. After 45 years, water oak averaged 96 feet (29.3 m) in
height, 15 inches (38 cm) in d.b.h., and had an average stocking of 96
trees per acre (237 trees/ha) . Water oak planted on
canal-excavated material along the Tennessee-Tombigbee Waterway had
intermediate survival (greater than 40 percent) and a mean growth of
44.7 inches (113.60 cm) in 5 years .
Importance to Livestock and Wildlife
Water oak provides cover, food, and habitat for wildlife. Cavity
nesters such as the red-bellied woodpecker, great crested flycatcher,
and hairy woodpecker nest in water oak snags . A tall midstory of
water oak within a pine forest provides habitat for the southern flying
Water oak acorns are eaten by many animals including squirrels,
chipmunks, waterfowl, blue jay, wild turkey, and northern bobwhite
[8,48]. Blue jays and squirrels cache acorns in the fall and return to
eat them in the winter [8,21,44]. Acorns of the black oak group are an
especially important food source in the winter because those of the
white oak group germinate soon after falling and, therefore, are
unavailable [41,44]. Deer browse water oak .
Wood Products Value
but on poor sites the wood is knotty, mineral stained, and often insect
damaged . Water oak veneer is used as plywood for fruit and
vegetable containers .
fiber, and 21.1 percent crude fat which makes them high in energy. They
are low in nitrogen and phosphorus .
limits palatability . In feeding trials to test acorn preference of
fox squirrels, water oak ranked sixth in preference among the 12
southeastern acorn species tested .
Quercus nigra, the water oak, is an oak in the red oak group (Quercus sect. Lobatae), native to the southeastern United States, from southern Delaware and south to the coastal areas of Maryland, Virginia, the piedmont of North Carolina, all of South Carolina, most of Georgia (with the exception of the Appalachian Mountains), all of Alabama, Mississippi, central Florida, and westward to Louisiana and eastern Texas. From there, northward to southeastern Missouri including Arkansas, eastern Oklahoma, parts of Tennessee, and extreme southwestern Kentucky. It occurs in lowlands and up to 450 m (1500 ft) altitude.
It is a medium-sized deciduous tree, growing to 30 m (100 ft) tall with a trunk up to 1 m (3 ft) in diameter. Young trees have a smooth, brown bark that becomes gray-black with rough scaly ridges as the tree matures. The leaves are alternate, simple and tardily deciduous, only falling well into winter; they are 3–12 cm (1–5 in) long and 2–6 cm (1/2–2 in) broad, variable in shape, most commonly shaped like a spatula being broad and rounded at the top and narrow and wedged at the base. The margins vary usually being smooth to shallowly lobed, with a bristle at the apex and lobe tips. The tree is easy to identify by the leaves, which have a lobe that looks as if a drop of water is hanging from the end of the leaf. The top of each leaf is a dull green to bluish green and the bottom is a paler bluish-green. On the bottom portion of the leaves, rusty colored hairs run along the veins. The acorns are arranged singly or in pairs, 10–14 mm (1/3-1/2 in) long and broad, with a shallow cupule; they mature about 18 months after pollination in fall of second year.
Water oak serves the same ecological role as weeping willow and other wetland trees. It is adapted to wet, swampy areas, such as along ponds and stream banks, but can also tolerate well-drained sites and even heavy, compacted soils. It grows in sandy soils, red clays, and old fields to the borders of swamps, streams, to bottomlands. Due to its ability to grow and reproduce quickly, the water oak is often the most abundant species in a stand of trees. The tree is relatively short-lived compared to other oaks and may live only 60 to 80 years. It does not compete well and does not tolerate even light shade. Water oak is frequently used to restore bottomland hardwood forests on land that was previously cleared for agriculture or pine plantations. Minimum age for flowering and fruiting is 20 years and the tree produces heavy crops of acorns nearly every year. Water oak is not recommended as an ornamental due to being short-lived, disease-prone, and extremely messy.
Hybrids of water oak are known with southern red oak (Quercus falcata), bluejack oak (Quercus incana), turkey oak (Quercus laevis), blackjack oak (Quercus marilandica), willow oak (Quercus phellos), Shumard oak (Quercus shumardii), and black oak (Quercus velutina)
Water oak acorns are an important food for white-tailed deer, eastern gray squirrel, raccoon, wild turkey, mallard, wood duck, and bobwhite quail. In winter, deer will browse the buds and young twigs.
Uses and history
Water oak has been used for timber and for fuel by people in the southern states since the 17th century. The wood is generally sold as "red oak", mixed with the wood from other red oaks.
Other names include spotted oak, duck oak, punk oak, orange oak or possum oak.
|Wikimedia Commons has media related to Quercus nigra.|
- Flora of North America: Quercus nigra
- C.Michael Hogan Ed. 2011. Quercus nigra. Encyclopedia of Life. Contributor Missouri Botanical Gardens
- USDA Forest Service
- Germplasm Resources Information Network: Quercus nigra
Trees with 3-lobed leaves with attenuate bases have been recognized as Quercus nigra var. tridentifera Sargent.
Quercus nigra reportedly hybridizes with Q . falcata (= Q . × garlandensis E. J. Palmer), Q . incana , Q . laevis (= Q . × walteriana Ashe), Q . marilandica (= Q . × sterilis Trelease), Q . phellos (= Q . × capesii W. Wolf), Q . shumardii (= Q . × neopalmeri Sudworth), and Q . velutina ( Q . × demarei Ashe). In addition, D. M. Hunt (1989) cited evidence of hybridization also with Q . arkansana , Q . georgiana , Q . hemisphaerica , Q . laurifolia , Q . myrtifolia , Q . palustris , Q . rubra , and Q . texana.
Names and Taxonomy
[25,50]. It has been placed within the subgenus Erythrobalanus or black
oak group. There are no recognized varieties, subspecies, or forms.
Water oak hybridizes with the following species [25,50]:
x Q. falcata (southern red oak) = Q. X garlandensis Palmer
x Q. incana (bluejack oak) = Q. X caduca Trel.
x Q. laevis (turkey oak) = Q. X walteriana Ashe
x Q. marilandica (blackjack oak) = Q. X sterilis Trel.
x Q. phellos (willow oak) = Q. X capesii W. Wolf
x Q. shumardii (Shumard oak) = Q. X neopalmeri Sudw.
x Q. velutina (black oak) = Q. X demarei Ashe
Quercus microcarpa Small
Quercus nigra var. heterophylla (Ait.) Ashe
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