BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus phellos | Willow Oak 



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 [9,30,34].


RAUNKIAER LIFE FORM : 
   Phanerophyte (mesophanerophyte)
   Phanerophyte (megaphanerophyte)


REGENERATION PROCESSES : 
Sexual:  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 [30].  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 [8].

Germination is hypogeal.  The best germination site is moist
well-aerated soil with 1 or more inches (2.5+ cm) of leaf litter [30].
An 8-week submersion in water slightly reduced the germination capacity
of willow oak acorns [20] but not enough to affect the species' ability
to regenerate an area [30].

Early height growth of seedlings is moderate.  On good sites, a seedling
will grow 4.5 feet (1.4 m) in 2 years [30].  Total height growth on a
peat swamp forest site was 4.3 feet (1.3 m) after four growing seasons.
On a wet flat (pocosin) forest site, total height growth was 6.7 feet (2
m) after 8 growing seasons [18].  Although moderately intolerant of
shade, seedlings will persist as long as 30 years under a forest canopy
[30].

Moisture must be available during the entire growing season for best
growth.  However, complete soil saturation during the growing season
inhibits root growth.  Willow oak seedlings averaging 9.8 inches (24.8
cm) in height survived a 60-day period of complete soil saturation, but
height growth was significantly (p < 0.01) reduced and there was some
mortality of secondary roots [14].  Older trees may survive up to 3
years of continuous flooding [13].  However, permanent standing water
kills the root system and eventually the tree [30].

Vegetative:  Willow oak sprouts readily from stumps of smaller trees
[30].


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
[6,30,34].

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 [15]. 

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 and a pH between 4.5 and 5.5.  The most common soils are in the
orders Inceptisols and Alfisols [30].  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 [30,34].

In addition to those species mentioned in Distribution and Occurrence,
overstory associates include red maple (Acer rubrum), cedar elm (Ulmus
crassifolia), eastern cottonwood (Populus deltoides), honeylocust
(Gleditsia triacanthos), persimmon (Diospyros virginiana), Nuttall oak
(Quercus nuttallii), chestnut oak (Q. prinus), and spruce pine (Pinus
glabra).  Shrub and small tree associates include swamp privet
(Forestiera acuminata), roughleaf dogwood (Cornus drummandii), hawthorn
(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.) [7,10,25,30].



SUCCESSIONAL STATUS : 
Facultative Seral Species

Willow oak is shade intolerant and responds well to release [30].

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 (Q. palustris) is found on
similar sites in the northern latitudes of the southern hardwood region
[10].

In the absence of fire, willow oak and laurel oak will expand into
wetland savannas in the Big Thicket area of east Texas and become a "pin
oak flat" [40].


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 [30].

Related categories for Species: Quercus phellos | Willow Oak