Crooked Run Valley
willow oak (Quercus phellos)
swamp willow oak
SCIENTIFIC SYNONYMS: There are no scientific synonyms for
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The currently accepted scientific name of willow oak is
Quercus phellos L. It has been placed within the black (red) oak group.
There are no recognized varieties, subspecies, or forms. Willow oak
hybridizes with the following species: black oak, southern red oak, bear
oak, blackjack oak, water oak, pin oak, northern red oak, Shumard oak,
and bluejack oak.
NATIVE STATUS: Native, United States.
GENERAL BOTANICAL CHARACTERISTICS: Willow oak is a
large, deciduous, graceful tree with a straight, tall, slender trunk and
willowlike leaves. The leaves are 5 to 8 times as long as wide, with no
lobes or undulations. This species is long-lived and shows moderately
rapid growth on good sites. It reaches 80 to 120 feet (24-37 m) in height
and 40 or more inches (100+ cm) in d.b.h. On alluvial soils, the feeder
roots are concentrated in the aerated layer above the saturated zone.
Roots do not penetrate the zone of free-standing water.
REGENERATION PROCESSES: Willow oak is monoecious. Acorn
production begins when the tree is about 20 years old. This species
produces a good acorn crop nearly every year. Dissemination is by
animals and water. Blue jays transport and cache acorns up to several
kilometers from the collection tree. Blue jays seem to prefer species
with small to medium-sized acorns, such as willow oak. The best
germination site is moist well-aerated soil with 1 or more inches (2.5+ cm)
of leaf litter.
Early height growth of seedlings is moderate. On good sites, a seedling
will grow 4.5 feet (1.4 m) in 2 years. Although moderately intolerant of
shade, seedlings will persist as long as 30 years under a forest canopy.
Moisture must be available during the entire growing season for best
growth. However, complete soil saturation during the growing season
inhibits root growth. Permanent standing water kills the root system
and eventually the tree.
Willow oak sprouts readily from stumps of smaller trees.
SITE CHARACTERISTICS: Willow oak grows primarily on floodplain
sites that are commonly flooded in the winter and spring, but only briefly
during the growing season. This species usually grows on ridges and high
flats of first bottoms which are the areas surrounding swamps and major
rivers which flood deeply and frequently, but drain rapidly because of relief.
It also grows along minor streams and on ridges, flats, and sloughs of second
bottoms which flood infrequently. It rarely occurs on uplands. Willow oak
is found in the forests on North Carolina's outer barrier islands, but it is
rarely encountered on South Carolina's outer barriers. Willow oak grows
best in moist alluvial soils that are deep, uncompacted, and relatively
undisturbed. The best soil is medium-textured, silty or loamy, and has at
least 2 percent organic material. The ideal depth of the water table during
the growing season is 2 to 6 feet (0.6-1.8 m). A water table less than 1 foot
(0.3m) or more than 10 feet (3 m) below the ground surface is unsuitable
for willow oak.
Overstory associates include red maple (Acer rubrum), cedar elm
(Ulmus crassifolia), eastern cottonwood (Populus deltoides), honey-
locust (Gleditsia triacanthos), persimmon (Diospyros virginiana) Nuttall
oak (Quercus nuttallii), chestnut oak (Quercus prinus), and spruce pine
(Pinus glabra). Shrub and small tree associates include swamp privet
(Forestiera acuminata), roughleaf dogwood (Cornus drummandii), haw-
thorn (Crataegus spp.), American hornbeam (Carpinus caroliniana), and
red mulberry (Morus rubra). Vines include Alabama supplejack
(Berchemia scandens), greenbrier (Smilax spp.), poison-ivy (Rhus radicans), peppervine (Ampelopsis arborea), trumpet-creeper (Campsis radicans),
crossvine (Anisostichus capriolata), and grape (Vitis spp.).
SUCCESSIONAL STATUS: Willow oak is shade intolerant and
responds well to release. The willow oak-water oak-laurel oak forest
cover type may represent a topographic or edaphic climax on terrace
flats and poorly drained flatwoods. These stands, known as "pin oak flats"
with very little vegetation growing beneath the oaks and water standing
much of the year, may be entirely willow oak. True pin oak (Quercus
palustris) is found on similar sites in the northern latitudes of the southern
SEASONAL DEVELOPMENT: Flowering takes place between
February and May, usually a week before the leaf buds open. Acorns
mature between August and October of their second year. Seeds
germinate the spring after seedfall.
GENERAL DISTRIBUTION: Willow oak occurs on the Atlantic and
Gulf coastal plains from New Jersey and southeastern Pennsylvania to
Georgia and northern Florida; west to east Texas; and north in the
Mississippi River valley to southeastern Oklahoma, Arkansas, southeastern
Missouri, southern Illinois, western and southern Kentucky, and eastern
Tennessee. Willow oak is absent from peninsular Florida and southeastern
SKY MEADOWS DISTRIBUTION:
Tree specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
A single specimen of willow oak occurs at the entrance booth of the park.
HABITAT TYPES AND PLANT COMMUNITIES: Willow oak is
commonly found in transitional communities between swamps and upland
mesic forests. The willow oak-water oak-laurel oak (Quercus laurifolia)
forest cover type is located topographically between the swamp chestnut
oak (Quercus michauxii) -cherrybark oak (Quercus falcata var. pagodi-
folia) type on the higher, better drained sites and the overcup oak (Quercus
lyrata) -water hickory (Carya aquatica) type on the lower, more poorly
drained sites. Within the willow oak-water oak-laurel oak type, willow oak
is generally located between laurel oak on the more poorly drained sites and
water oak on the better drained sites.
IMPORTANCE AND USES: The consistent and abundant acorn crops
of willow oak are an important food source for wildlife including waterfowl,
wild turkey, blue jays, red-headed and red-bellied woodpeckers, flickers,
grackles, white-tailed deer, fox and gray squirrels, and other small rodents.
It produces a large acorn crop almost every year. 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. Willow oak is considered good browse for white-tailed deer.
Willow oak is used for restoration of the wetter sites of bottomland
hardwood forests and for rehabilitation of disturbed areas. It is also a
good species to plant along margins of fluctuating-level reservoirs.
Willow oak is an important source of lumber and pulp. It has good pulp
characteristics and can be harvested when quite young.
This species is used widely as a shade tree and ornamental. It transplants