Iron Oak

Quercus stellata is often identified by its commonly cross-shaped leaf form, particularly in the eastern part of its range. All individuals and populations do not express this characteristic, however. Moreover, Q . stellata has broad overlap with Q . margaretta and even with some forms of the blackjack oak, Q . marilandica , one of its most common associates. The thick yellowish twigs with indument of stellate hairs and the dense harsh stellate hairs on the abaxial leaf surface are better diagnostic characteristics when variation includes leaf forms that are not obviously cruciform.

Native Americans used Quercus stellata medicinally for indigestion, chronic dysentery, mouth sores, chapped skin, hoarseness, and milky urine, as an antiseptic, and as a wash for fever and chills (D. E. Moerman 1986).

Putative hybrids are known with Quercus marilandica , Q . alba , and various other white oaks. Quercus stellata is also one of the few oaks that appears to produce hybrids with species in the live oak group, although obvious intermediates are rarely encountered. Nothospecies names based on putative hybrids involving Q . stellata include: Q . × stelloides E. J. Palmer (= Q . prinoides × Q . stellata ), Q . × mahloni E. J. Palmer (as Q . sinuata var. breviloba × Q . stellata ), Q . × pseudomargaretta Trelease (= Q . margaretta × Q . stellata ), Q . × sterretti Trelease (= Q . lyrata × Q . stellata ), Q . × macnabiana Sudworth (= Q . sinuata × Q . stellata ), Q . × guadalupensis Sargent (= Q . sinuata × Q . stellata ), Q . × fernowi Trelease (= Q . alba × Q . stellata ), and Q . × bernardensis W. Wolf (= Q . montana × Q . stellata ).

Trees , deciduous, to 20(-30) m. Bark light gray, scaly. Twigs yellowish or grayish, (2-)3-5 mm diam., densely stellate-pubescent. Buds reddish brown, ovoid, to 4 mm, apex obtuse or acute, sparsely pubescent. Leaves: petiole 3-15(-30) mm. Leaf blade obovate to narrowly obovate, elliptic or obtriangular, 40-150(-200) × 20-100(-120) mm, rather stiff and hard, base rounded-attenuate to cordate, sometimes cuneate, margins shallowly to deeply lobed, lobes rounded or spatulate, usually distal 2 lobes divergent at right angles to midrib in cruciform pattern, secondary veins 3-5 on each side, apex broadly rounded; surfaces abaxially yellowish green, with crowded yellowish glandular hairs and scattered minute, 6-8-rayed, appressed or semi-appressed stellate hairs, not velvety to touch, adaxially dark or yellowish green, dull or glossy, sparsely stellate, often somewhat sandpapery with harsh hairs. Acorns 1-3, subsessile or on peduncle to 6(-40) mm; cup deeply saucer-shaped, proximally rounded or constricted, 7-12(-18) mm deep × (7-)10-15(-25) mm wide, enclosing 1/4-2/3 nut, scales tightly appressed, finely grayish pubescent; nut light brown, ovoid or globose, 10-20 × 8-12(-20) mm, glabrous or finely puberulent. Cotyledons distinct.

Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va.

Flowering spring.

Usually on xeric sites, dry gravelly and sandy ridges and uplands, dry clays, prairies and limestone hills, woodlands and deciduous forests; 0-750m.

Quercus minor (Marshall) Sargent; Q. obtusiloba Michaux

Quercus stellata is an oak in the white oak group. It is a small tree, typically 10–15 m tall and 30–60 cm trunk diameter, though occasional specimens reach 30 m tall and 140 cm diameter. It is native to the eastern United States, from Connecticut in the northeast, to central Texas in the southwest. It is one of the most common oaks in the southern part of the eastern prairies, such as in the Cross Timbers. Quercus stellata is often identified by its commonly cross-shaped leaf form, particularly in the eastern part of its range. All individuals and populations do not express this characteristic, however. Moreover, Q . stellata has broad overlap with Q . margaretta and even with some forms of the blackjack oak, Q . marilandica, one of its most common associates. The thick yellowish twigs with indument of stellate hairs and the dense harsh stellate hairs on the abaxial leaf surface are better diagnostic characteristics when variation includes leaf forms that are not obviously cruciform.

More info for the terms: forest, fuel, surface fire

Post oak in a savanna is more likely to be killed by surface fires than
post oak in a forest because of the grass fuel load in the savanna. In a
March surface fire in a central Oklahoma savanna, most post oaks smaller
than 1.6 inches (4 cm) in d.b.h. were top-killed and some trees up to
3.5 inches (9 cm) in d.b.h. were top-killed or severely damaged. In the
adjacent post oak-blackjack oak forest, however, few woody stems larger
than 1 inch (2.5 cm) were top-killed [24].

In a post oak-eastern redcedar community, post oak is likely to be
killed by fire because the eastern redcedar is highly flammable and
fires tend to be hot. In a severe fire in a post oak-eastern redcedar
community in the Wichita Mountains of Oklahoma, 92 percent of all trees
(post oak, blackjack oak, and eastern redcedar) greater than 3 inches
(7.6 cm) in d.b.h. were top-killed and only 13.5 percent of the post
oaks and blackjack oaks sprouted. In the adjacent post oak-blackjack
oak forest, only 66 percent of trees greater than 3 inches (7.6 cm) were
top-killed by the fire and 70 percent sprouted [40].

post oak
Delta post oak
iron oak
cross oak
dwarf post oak
runner oak
scrubby post oak
Boynton post oak
Drummond post oak
bottomland post oak
bottom-land post oak
Mississippi Valley oak
yellow oak

More info for the term: tree

Post oak is a long-lived, native, deciduous tree with a crown of
horizontal branches. The varieties are distinguished by leaf shape,
acorn size, growth form, and site preferences. The typical variety
usually grows 50 to 60 feet (15.2-18.3 m) in height and 12 to 24 inches
(30-61 cm) in d.b.h. It rarely exceeds 100 feet (30.5 m) in height and
48 inches (122 cm) in d.b.h. [47]. In the drier areas of its range
(Texas), post oak is typically only 30 to 40 feet (9-12 m) tall and 15
to 18 inches (38-46 cm) in d.b.h. Post oak is slow growing and lives
300 to 400 years [24,47]. Seedlings have especially thick taproots.
Most roots develop above underlying clay horizons [47].

Delta post oak is generally larger than the typical variety, growing to
about 100 feet (30 m) in height [13,46].

More info for the term: tree

Post oak is widespread in the eastern and central United States from
southeastern Massachusetts, Rhode Island, southern Connecticut, and
extreme southeastern New York; south to central Florida; and west to
southeastern Kansas, western Oklahoma, and central Texas. In the
Midwest, it grows as far north as southeastern Iowa, central Illinois,
and southern Indiana. It is an abundant tree in coastal plains and the
Piedmont and extends into the lower slopes of the Appalachian Mountains
[47].

Delta post oak occurs in bottomlands in eastern Texas and in the
Mississippi River valley in western Mississippi, southeastern Arkansas,
and Louisiana [47].

More info for the terms: fire regime, forest, fuel, fuel moisture, litter, root collar, surface fire, tree, xeric

Post oak is moderately resistant to fire [5]. It is less tolerant than
blackjack oak, about as tolerant as black oak [5,21], and slightly more
tolerant than southern red oak [3]. The basal bark on mature trees is
medium thick, and stands of post oak are moderately open [5]. Smaller
trees are easily killed by fire, but sprout vigorously from the root
collar [55].

If fire is frequent in pine-oak-hickory associations, post oak is an
important constituent because fire provides an opportunity for invasion
by this more fire-resistant oak. If fire is infrequent or absent, post
oak also is absent [28].

In xeric sandhill communities of post oak, blackjack oak, and bluejack
oak, grass and other fuels are rare and fires are only occasional. When
fires do reach these communities, some mature trees may be killed, but
they sprout and the community is maintained [54].

In a study investigating the temperature of a surface fire as it moved
from the surrounding grasslands to the area beneath a single post oak,
the temperature increased sharply from the canopy edge to the midcanopy
position because the increase in fuel load was not accompanied by a
concomitant increase in fuel moisture percentage. The temperature then
decreased from the midcanopy to the base of the tree, despite continued
increase in fuel load and a slight decrease in fuel moisture. This
decline in temperature was presumably caused by the bole of the tree,
which stopped the leading edge of the fire [16].

Under historic FIRE REGIMES, a savanna is maintained because after a hot
surface fire grass grows back faster than the woody sprouts. In the
absence of fire, the woody canopy spreads and the grass dies back. If
fire returns, post oaks are likely to survive because the reduction in
grass fuel results in a much cooler fire. In a fire in central
Oklahoma, all savanna litter burned whereas only 45 percent of the
litter in the adjacent forest burned [24].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the terms: fire suppression, forest, fuel, prescribed fire, tree

Many present-day post oak-blackjack oak stands were former savannas. In
the Wichita Forest Reserve in Oklahoma, the average age of stands
coincides with the advent of fire suppression in the reserve [10].
Forests may not revert back to savannas with prescribed burning because
post oak-blackjack oak forests are resistant to effects of fire once the
canopy closes and the grass fuel load is reduced [24]. Fire, in
conjunction with herbicides, may be effective at eliminating post oak
[48].

Prescribed fires are used to maintain grasslands. Repeat summer fires
are effective at controlling woody species because they are hotter than
winter fires, and belowground carbohydrate reserves are lowest in the
summer [18]. Post oak growing within a pine forest can also be
controlled with prescribed fire [3,53].

Equations for the estimation of fire-caused mortality have been
developed for post oak. In order to predict mortality, a manager needs
to know the tree d.b.h, the height of bark blackening, the width of bark
blackening 1 foot above the ground, and the season of fire. The
equations should only be applied to trees between 3 and 16 inches
(7.6-40.6 cm) in d.b.h. [31].

More info on this topic.

More info for the term: phanerophyte

Phanerophyte

More info for the terms: mesic, serpentine soils

Post oak occurs primarily on dry uplands with southerly or westerly
exposures [47] but may occur on terraces of smaller streams in
well-drained soil [23]. Post oak is common to about 2,950 feet (900 m)
in elevation throughout its range and rare to about 4,920 feet (1,500 m)
in the southern Appalachian Mountains [13,47].

The soils are usually shallow, well-drained, coarse-textured, and
deficient in nutrients and organic matter. It commonly grows in
serpentine soils [56,58]. Post oak is often restricted to sites where a
heavy clay subsurface layer is within 1 foot (0.3 m) of the surface or
bedrock is within 2 to 3 feet (0.6-0.9 m) of the surface [25]. It may
grow in shallow sand overlying beds of clay or gravel, but the typical
variety of post oak appears to be restricted from deep sands [35]. Post
oak grows on drier clayhills that formerly supported longleaf pine
(Pinus palustris) [36].

Post oak occurs on sites too dry for white oak and southern red oak (Q.
falcata) [38], but on slightly more mesic sites than blackjack oak [11]
or eastern redcedar (Juniperus virginiana) [17]. Generally, excessive
soil moisture and inundation cause high mortality or severe stress to
post oak [6]; however, it dominates some flatwoods in southern Indiana
that are moist in the winter [9].

Delta post oak occurs in rich, moist bottomlands, usually on the highest
first bottom ridges and terraces. Soils are fine, sandy loam [13,47].

In addition to those species mentioned in Distribution and Occurrence,
less common overstory associates of post oak include hickories (Carya
spp.), southern red oak, scarlet oak, bluejack oak, live oak, shingle
oak (Q. imbricaria), chinkapin oak (Q. muehlenbergii), bluejack oak,
Shumard oak (Q. shumardii), blackgum (Nyssa sylvatica), sourwood
(Oxydendrum arboreum), red maple (Acer rubrum), winged elm (Ulmus
alata), hackberry (Celtis occidentalis), and dogwood (Cornus spp.) [47].

Overstory associates of Delta post oak include green ash (Fraxinus
pennsylvanica), white ash (F. americana), white oak, water oak,
blackgum, sweetgum (Liquidambar styraciflua), American elm (Ulmus
americana), winged elm, American hornbeam (Carpinus caroliniana),
American sycamore (Platanus occidentalis), black willow (Salix nigra),
and hickories [46,47].

More info on this topic.

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

40 Post oak - blackjack oak
43 Bear oak
44 Chestnut oak
45 Pitch pine
46 Eastern redcedar
51 White pine - chestnut oak
52 White oak - black oak - northern red oak
53 White oak
68 Mesquite
69 Sand pine
70 Longleaf pine
71 Longleaf pine - scrub oak
72 Southern scrub oak
75 Shortleaf pine
76 Shortleaf pine - oak
78 Virginia pine - oak
79 Virginia pine
80 Loblolly pine - shortleaf pine
81 Loblolly pine
82 Loblolly pine - hardwood
83 Longleaf pine - slash pine
84 Slash pine
91 Swamp chestnut oak - cherrybark oak
110 Black oak

More info on this topic.

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
FRES15 Oak - hickory
FRES16 Oak - gum - cypress
FRES32 Texas savanna
FRES39 Prairie

More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: forest

K082 Mosaic of K074 and K100
K083 Cedar glades
K084 Cross Timbers
K089 Black Belt
K100 Oak - hickory forest
K104 Appalachian oak forest
K110 Northeastern oak - pine forest
K111 Oak - hickory - pine forest
K112 Southern mixed forest
K113 Southern floodplain forest
K115 Sand pine scrub

More info for the terms: low-severity fire, top-kill

In general, small post oaks are top-killed by low-severity fire, and
more severe fires top-kill larger trees and may kill rootstocks as well.

Growing-season fires tend to be more detrimental to post oak than
dormant-season fires. In Texas, a winter head fire top-killed 20 percent
of a post oak and southern red oak understory; a late winter fire
top-killed just over 40 percent; a spring fire top-killed just under 40
percent; and a late summer fire top-killed 55 percent. Winter fires
killed on average less than 2 percent of rootstocks; summer fires killed
on average less than 10 percent. The top-kill was substantially greater
for oaks between 0.6 and 2.5 inches (1.5-6.4 cm) in diameter than those
between 2.6 and 4.5 inches (6.5-11.4 cm) in diameter. Diameter was
measured 6 inches (15.2 cm) above the ground line [15].

More info for the term: cover

Post oak provides cover and habitat for birds and mammals. Cavities
provide nest and den sites, and leaves are used for nest construction.
The acorns are an important food source for wildlife including
white-tailed deer, wild turkey, and squirrels and other rodents [47].

The tannin in leaves, buds, and acorns is toxic to sheep, cattle, and
goats [47].

More info for the terms: codominant, forest, natural, tree

Post oak occurs as a dominant tree in savannas and in forests adjacent
to grasslands. It forms pure stands or mixed stands with blackjack oak
(Quercus marilandica) in the prairie transition area of central Oklahoma
and Texas, where the eastern deciduous forests grade into the drier
western grasslands [43,47].

The following published classifications list post oak as a dominant or
codominant species:

Forest vegetation of the lower Alabama Piedmont [22]
The natural communities of South Carolina [37]
Forest vegetation of the Big thicket, southeast Texas [33]
Eastern Deciduous Forest [52]
Old-growth forests within the Piedmont of South Carolina [25]
The natural forests of Maryland: an explanation of the vegetation map of
Maryland [56]

More info for the term: tree

Tree

More info for the terms: competition, hardwood

Post oak is susceptible to most insects and diseases that attack eastern
oak species. Chestnut blight fungus (Cryphonectria parasitica) attacks
post oak throughout most of its range [47].

Gypsy moth (Lymantria dispar), which has defoliated and killed
northeastern oak species, showed 17 percent survival in feeding trials
using post oak. This exotic moth has been spreading southward from New
England and, if not contained, could become a problem for post oak
[34].

Hardwood competition in pine plantations and hardwood expansion into
grasslands are often controlled with herbicides. Tebuthiuron and
triclopyr are extremely effective on post oak in grasslands of the Cross
Timbers area of Oklahoma [48].

Post oak acorns contain 5.2 percent crude fat, 37.9 percent total
carbohydrates, 3.8 percent total protein, 0.08 percent phosphorus, 0.25
percent calcium, and 0.06 percent magnesium [2].

AL AR CT DE FL GA IA IL IN KS
KY LA MA MD MS MO NC NJ NY OH
OK PA RI SC TN TX VA WV

More info for the term: tree

Post oak is used as a shade tree and its bark is used for decorative and
protective mulch in landscaping [47].

Among 12 southeastern oak species, post oak ranked third in preference
to the fox squirrel [39]. Acorns of white oak group species are
generally more palatable than black oak group acorns [45].

More info on this topic.

Post oak flowers from March to June depending on elevation and latitude.
Flowers appear at the same time as leaves. Acorns mature in one growing
season and drop soon after ripening from September through November.
Acorns exhibit no dormancy and germinate soon after dropping [47].

More info for the terms: density, fire frequency, forest, frequency, hardwood, root crown

If top-killed by fire, post oak up to 10 inches (25 cm) in d.b.h. sprout
vigorously from the root crown [47].

Because of sprouting, fire tends to increase the number of understory
post oak stems. Eight annual winter fires in Tennessee resulted in
2,000 stems per acre (4,940/ha) compared to 1,220 stems per acre
(3,010/ha) in the unburned control [49]. If the high fire frequency
continues, however, the stem density may decrease as root systems are
killed. In a study on the Santee Experimental Forest in South Carolina,
43 years of periodic winter and summer low-severity fires and annual
winter and summer low-severity fires reduced the number of hardwood
stems (including post oak) between 1 and 5 inches (2.6-12.5) in d.b.h.
However, the number of stems less than 1 inch (2.5 cm) in d.b.h.
increased slightly under all treatments except annual summer fires.
Root systems were weakened and eventually killed by annual burning
during the growing season [53].

Fire wounds on surviving trees allow entry of fungi which can cause
heart rot decay [50].

Tree with adventitious-bud root crown/root sucker

More info for the terms: hypogeal, litter, monoecious, root crown, seed, tree

Sexual: Post oak is monoecious. Seed production begins when the tree
is about 25 years old. Good crops occur at 2- to 3-year intervals.
Post oak does not produce as many acorns as white oak, blackjack oak,
black oak (Quercus velutina), or scarlet oak (Q. coccinea) [47].

Acorns germinate in autumn soon after falling. Germination is hypogeal.
The ideal seedbed is moist soil covered with 1 inch (2.5 cm) or more of
leaf litter. Height and diameter growth are slow; 10 year d.b.h. growth
generally averages less than 2 inches (5 cm). Post oak usually grows
more slowly than any associated trees except blackjack oak [47].
Average annual height growth of seedlings in Missouri during a 6 year
period was 2.5 inches (6.4 cm) [29].

Seedlings are resistant to drought but not to flooding [47]. Post oak
seedlings were more drought tolerant than white oak, black oak, or
northern red oak (Q. rubra), primarily because of greater drought
tolerance of leaf and root cells [57].

Vegetative: Trees up to 10 inches (25 cm) in d.b.h. sprout prolifically
from the root crown after being top-killed. Post oak tends to have
fewer sprouts per clump than black, chestnut, white, or scarlet oaks
[47]. Post oak sprouts grow faster than seedlings [29]. In the Cross
Timbers area of Oklahoma, post oak often occurs in small clusters of two
to six trees. These clusters may represent a single individual because
the species occasionally reproduces vegetatively from roots, especially
under moisture stress [8].

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

14 Great Plains

More info on this topic.

More info for the terms: association, climax, codominant, competition, forest, xeric

Post oak is intolerant of shade and competition. Because of slow growth
it is often overtopped by other species, including most oaks. It
persists and becomes dominant on poor sites because of its drought
resistance [47]. Delta post oak is moderately intolerant of shade [41].

Post oak is common in the understory of pine (Pinus spp.)-hardwood
forests. In the absence of fire, post oak may become dominant depending
on site conditions and competition from associated species [19]. In an
upland longleaf pine forest in the west Gulf Coastal Plain, post oak,
along with blackjack oak, bluejack oak, and black hickory (Carya
texana), became codominant and eventually replaced longleaf pine [4].

Post oak will expand into adjacent prairies in the absence of fire [47].
The post oak-blackjack oak association may be an edaphic climax on dry
sites [14].

Some of the most xeric sites of the South Carolina Piedmont are occupied
by old-growth communities of post oak, black oak, and Blue Ridge blueberry
(Vaccinium vacillans). Although the community appears to be in steady
state, it may evolve into a hickory-dominated community in the absence
of fire [25].

Quercus boyntonii Beadle
Quercus mississippiensis Ashe
Quercus similis Ashe
Quercus drummondii Liebm.
Quercus stellata var. boyntonii (Beadle) Sarg.
Quercus stellata var. mississippiensis (Ashe) Little
Quercus stellata var. similis (Ashe) Sudw.

The currently accepted scientific name of post oak is Quercus stellata
Wangenh. [30,47]. Post oak has been placed within the subgenus
Lepidobalanus, or white oak group [59].

The following varieties are recognized [30]:

Quercus stellata var. paludosa Sarg., Delta post oak
Quercus stellata var. stellata, post oak

Identification of post oak is difficult because of its many growth
forms. At times, local populations have been given species or varietal
status. A rhizomatous dwarf post oak that grows near Lufkin, Texas, is
called Boynton post oak (Q. boyntonii). Drummond post oak, which grows
in deep sands of Texas, is thought to be a hybrid between post oak and
sand post oak (Q. margaretta) [46]. It has also been considered a species (Q.
drummondii) by some authors [13,46].

Post oak hybridizes with the following species [30]:

x Q. alba (white oak): Q. X fernowii Trel.
x Q. bicolor (swamp white oak): Q. X substellata Trel.
x Q. durandii (Durand oak): Q. X macnabiana Sudw.
x Q. havardii (Havard oak)
x Q. lyrata (overcup oak): Q. X sterrettii Trel.
x Q. macrocarpa (bur oak): Q. X guadalupensis Sarg.
x Q. minima (dwarf live oak): Q. X neo-tharpii A. Camus
x Q. mohriana (Mohr oak)
x Q. prinoides (dwarf chinkapin oak): Q. X stelloides Palmer
x Q. prinus (chestnut oak): Q. X bernardiensis W. Wolf
x Q. virginiana (live oak): Q. X harbisonii Sarg.

Post oak is planted for soil stabilization on dry, sloping, stony sites,
which are unsuitable for other species [47].

More info for the term: natural

Post oak is not a preferred timber species [44]. It is difficult to
grade because of insect damage, and natural pruning and growth are slow
[41]. The wood is very durable and classified as moderately to very
resistant to decay. It is used for railroad ties, mine timbers,
flooring, siding, lathing, planks, construction timbers, and fence posts
(hence its name) [47]. Wood of Delta post oak is of better quality than
that of the typical variety, but it has a distinct yellow-tan cast which
requires separate handling as veneer. Otherwise, Delta post oak wood
has broad utility [41].

In the Northern Forest Region, post oak is found in the forest cover type White Pine-Chestnut Oak (Society of American Foresters Type 51) (4). On dry ridges and upper slopes its other associates are scarlet, white, and black oaks (Quercus coccinea, Q. alba, and Q. uelutina), hickories (Carya spp.), and pines (Pinus spp.).

In the Central Forest Region, post oak is most abundant in Post Oak-Blackjack Oak (Type 40). It extends over a wide area from eastern Kansas south to Texas and east to the Atlantic Coastal Plain. On heavier, clay soils a post oak variant of this type is found, and in the Texas "Cross Timbers" area and in Oklahoma, a post oak savanna. Along with other oaks, post oak is a common associate in several other cover types: Bear Oak (Type 43), Chestnut Oak (Type 44), White Oak-Black Oak-Northern Red Oak (Type 52), White Oak (Type 53), Black Oak (Type 110), Pitch Pine (Type 45), and Eastern Redcedar (Type 46).

In the Southern Forest Region, sand post oak is a chief hardwood component of Sand Pine (Type 69). Sand post oak and post oak grow on drier sites of Longleaf Pine (Type 70) and in Southern Scrub Oak (Type 72). Post oak is a common associate in Longleaf Pine-Slash Pine (Type 83), Shortleaf Pine (Type 75), Virginia Pine (Type 79), Loblolly Pine (Type 81), and Loblolly Pine-Shortleaf Pine (Type 80), and on better drained sites of Slash Pine (Type 84). In the oak-pine types post oak is a common associate in Shortleaf Pine-Oak (Type 76), Virginia Pine-Oak (Type 78), and the Loblolly Pine-Hardwood (Type 82); sand oak is an important component of Longleaf Pine-Scrub Oak (Type 71).

Delta post oak is found in Swamp Chestnut Oak-Cherrybark Oak (Type 91). In Mesquite (Type 68) of east central Texas, post oak appears in mixture with mesquite (Prosopis spp.).

The most common hardwoods associated with typical post oak are blackjack oak (Quercus marilandica), black oak, and the hickories. Less common associates include southern red oak (Q. falcata), white oak, scarlet oak, chestnut oak (Q. prinus), shingle oak (Q. imbricaria), live oak (Q. uirginiana), chinkapin oak (Q. muehlenbergii), bluejack oak (Q. incana), Shumard oak (Q. shumardii), blackgum (Nyssa sylvatica), sourwood (Oxydendrum arboreum), red maple (Acer rubrum), winged elm (Ulmus alata), hackberry (Celtis occidentalis), chinkapin (Castanea spp.), and dogwood (Cornus spp.). Coniferous associates are eastern redcedar (Juniperus virginiana), shortleaf pine (Pinus echinata), Virginia pine (P. virginiana), pitch pine (P. rigida), loblolly pine (P. taeda), and occasionally longleaf and slash pines (P. palustris and P elliottii). At higher elevations eastern white pine (P. strobus) and hemlock (Tsuga spp.) are sometimes associates.

Delta post oak is commonly associated with cherrybark oak (Quercus falcata var. pagodifolia), water oak (Q. nigra), willow oak (Q. phellos), swamp chestnut oak (Q. michauxii), white oak, sweetgum (Liquidambar styraciflua), blackgum, American elm (Ulmus americana), winged elm, white ash (Fraxinus americana), hickories, and loblolly pine.

In the South, where post oak is a major component in many stands, the following small trees are common associates: shining sumac (Rhus copallina), smooth sumac (R. glabra), gum bumelia (Bumelia lanuginosa), hawthorns (Crataegus spp.), yaupon (Ilex vomitoria), possumhaw (J. decidua), redbud (Cercis canadensis), and rusty blackhaw (Viburnum rufidulum).

The range of post oak reaches from the humid East to semiarid portions of Oklahoma and Texas. Within this region, average annual precipitation varies from more than 1520 mm (60 in) in west Florida and parts of Louisiana to less than 560 mm (22 in) in central Texas. Annual snowfall varies from 760 cm (30 in) in southeastern Iowa to a trace in Florida (15).

Mean annual temperatures vary from 10' C (50' F) in southern New England and southeastern Iowa to 22' C (72' F) in central Florida. January temperatures average from -6' C (22' F) in southeastern Iowa to 17' C (62' F) in Florida; in July they range from 23' C (73' F) in southern New England to 290 C (85' F) in Texas. Temperature extremes of -11' C (12' F) in Kansas, Oklahoma, and Texas and -400 C (-40' F) in central Missouri have been recorded.

From northwest to southeast the average frost-free period increases from 165 to 300 days, 60 to 90 percent, respectively, of the annual precipitation occurring during this period.

Post oak is susceptible to most insects, diseases, and pollutants that present a threat to other oaks. Regeneration efforts are hampered by acorns being destroyed by weevils. Insect defoliators, leafrollers, tent caterpillars, Gypsy moth, sawfly, leaf miners, and skeletonizers may cause growth losses, and when repeated, may cause mortality (14). The foliage also is susceptible to at tacks by aphids, lace bugs, various scales, gall wasps, and mites. The trunk, twigs, and roots may be damaged by carpenterworms, borers, beetles, twig pruners, white grubs, and cicadas (locusts). Some of these cause defects that render the wood unfit for many commercial purposes (1).

Chestnut blight fungus (Cryphonectria parasitica) causes many defects as well as mortality to post oak throughout its range (8). The tree also is subject to oak wilt (Ceratocystis fagacearum), a vascular disease prevalent mostly north of the 35th parallel, but not to the same degree as on red oaks. Soil-inhabiting fungi may cause heavy seedling mortality by damping off. Powdery mildews stunt and deform nursery seedlings.

Many fungi produce spots, blotches, blisters, and blights on the foliage. They rarely cause real damage but are unsightly.

Decay fungi cause cankers, rots, and discoloration of the upper and lower stem, as well as of the roots. The Texas root rot (Phymatotrichum ormnivorum) attacks mainly oaks planted on old farm fields or in subdivisions (14).

Several species of mistletoe are often found on branches and trunks of post oak. Infected branches may be stunted and eventually die. Trees usually are not killed.

Nonpoint source pollutants near large cities cause twigs of many oaks to die back, or kill the trees. The specific diagnosis is usually difficult. Sulfur dioxide, fluoride, ammonia, and some herbicides have been identified as probable agents.

Post oak is monoecious; staminate and pistillate flowers are on the same tree in separate catkins (aments). Flowers appear at the same time as the leaves. Flowering usually begins in March in the South and extends through May further north. Staminate flowers are borne in pendant catkins 5 to 10 cm (2 to 4 in) long. The calyx is yellow, pubescent, and five-lobed; the lobes are acute and laciniately segmented, with four to six stamens and pubescent anthers. Pistillate catkins are short-stalked or sessile and inconspicuous; the scales of the involucre are broadly ovate and hairy with red, short, enlarged stigmas (18).

The acorns mature in one growing season and drop soon after ripening, from September through November. Late freezes after the start of flowering and leafing may cause seed crop failures. The acorns are sessile or short-stalked, borne solitary, in pairs, or clustered; acorns are oval or ovoid-oblong, broad at the base, 13 to 19 mm (0.5 to 0.75 in) long, striate, set in a cup one-third to one-half its length. The cup is bowl-shaped, pale, and often pubescent within. Externally it is hoary-tomentose. The scales of the cup are reddish brown, rounded or acute at the apex, and closely appressed (18).

The great variation in post oak and its tendency to hybridize creates a number of varieties and hybrids. The following hybrids with Quercus stellata have been recognized (10): Q. alba (Q. x fernowii Ti-el.); Q. bicolor (Q. x substellata Trel.); Q. durandii (Q. x macnabiana Sudw.); Q. havardii (unnamed); Q. lyrata (Q. x sterrettii Trel.); Q. macrocarpa (Q. x guadalupensis Sarg.); Q. minima (Q. x neo-tharpii A. Camus); Q. mohriana (unnamed); Q. prinoides (Q. x stelloides Palmer); Q. prinus (Q. x bernardiensis W. Wolf); Q. virginiana (Q. x harbisonii Sarg.).

In the Southeast, mature post oaks are from 15.2 to 18.3 m (50 to 60 ft) tall and from 30 to 61 cm (12 to 24 in) in d.b.h. Maximum height rarely exceeds 30 m (100 ft), and diameters exceeding 122 cm (48 in) are uncommon. In the extreme western part of its range, mature trees are seldom larger than 9 to 12 in (30 to 40 ft) tall and 38 to 46 cm (15 to 18 in) in d.b.h. Height and diameter growth for post oak are usually slower than for any of the associated trees except blackjack oak ' Ten-year diameter growth generally averages less than 5 cm (2 in), and in central Oklahoma it may be only 13 mm (0.5 in).

Diameter growth of individual post oaks averaging 17 cm (6.7 in) in d.b.h. was stimulated when most of the stand was removed to favor forage production in Robertson County, TX (12). Post oak stands were thinned from an average of 14.9 m²/ha (65 ft² /acre) basal area to 8.9, 6.0, and 3.0 m²/ha (39, 26, and 13 ft² /acre). In the two ensuing growing seasons, average annual diameter growth for the heaviest thinning was twice that of the uncut check plots (3.6 mm. compared to 1.8 mm, excluding bark, or 0.14 in compared to 0.07 in).

Average post oak stands in east Texas contain a volume of about 47.2 m³/ha (7.5 cords or 675 ft³/acre). In an Oklahoma woodland, typical of the dry upland post oak type, post oaks 30 cm (12 in) in d.b.h. and larger made up 64 percent of the sawtimber volume (Doyle rule) in a stand averaging nearly 28.0 m³/ha (2,000 fbm/acre). The average post oak contained 0.4 m' (70 fbm).

Post oak is intolerant of competition and is classed as intolerant of shade. Because of its slow height growth it often is overtopped by other trees, including most other oaks. On poor sites, however, post oak tends to persist and become dominant because it is more drought resistant than many of its associates (12).

Post oak seedlings have especially thick taproots, usually exceeding the shoot diameter; but overall root development is less than that of northern red (Quercus rubra), scarlet, white, and blackjack oak (12). Although post oak seedlings do become established on sites having a tight clay subsoil, their growth is slow and most roots develop above the underlying clay (3). Post oak seedlings were found to be the most drought resistant of four Missouri oaks, primarily because of the greater drought tolerance of their leaf and root cells (13). In Alabama, post oak was the least tolerant of flooding of all species tested (6).

In common with many other oaks, post oak begins to bear acorns when it is about 25 years old. Good acorn crops are produced at 2- to 3-year intervals; although at several locations in Missouri over a 6-year period, post oak consistently averaged only 200 seeds per tree per year while white, blackjack, black, and scarlet oaks of the same size on the same site bore from 500 to 2,400 acorns per tree. Isolated trees in open fields in east Texas consistently produced well. Elsewhere in Texas, trees less than 15 cm (6 in) in d.b.h. had no acorns (12).

The number of post oak acorns per kilogram averages 838 (380/lb) but may range from 441 to 1,340 (200 to 608/lb) (17).

In a sampling of post oak acorn yields from 736 trees for 18 years (1950-67) in western Louisiana and eastern Texas, the average number of fresh acorns per kilogram was 476 (216/lb) with 39 percent moisture content (5). Mast yield increased linearly with increasing bole size. Expected acorn yield was 1.6 kg (3.6 lb) from trees 30.5 cm (12 in) in d.b.h., and 3.6 kg (8.0 lb) from trees 50.8 cm (20 in) in d.b.h. The percentage of acorn-producing trees also increased with increasing d.b.h. from 42 percent on 15.2 cm (6 in) trees to 76 percent on 55.9 cm (22 in) trees. Expected acorn yield rose from 0.9 kg (2 lb) on trees with a 3.0 ni (10 ft) crown diameter to 5.5 kg (12.1 lb) on trees with a 6.1 m (20 ft) crown diameter. Average acorn yield per tree over the 18-year observation period varied from a low 0.03 kg (0.07 lb) in 1962 to a high 4.4 kg (9.7 lb) in 1965.

Post oak acorns germinate in the autumn soon after dropping. They do not exhibit dormancy. Germination is hypogeal. The best seedbed is a moist soil covered with 2.5 cm (I in) or more of leaf litter.

Post oak grows on a variety of sites and soils. Its range coincides mostly with that of the Utisols but also includes some Alfisols in the western portion of its distribution. Typically, it grows on dry sites. Rocky outcrops, ridges, and upper slopes with southerly or westerly exposures are common.

Soils are generally well drained, sandy, coarse textured, deficient in nutrients, and low in organic matter. The surface soil is generally thin but post oak, and especially the scrubby sand post oak, grows on deep sandy, gravelly soils.

Delta post oak grows in fine sandy loam soils on the highest first-bottom ridges in terraces. There is seldom standing water, but the site may be wet due to slow drainage.

Post oak is a valuable contributor to wildlife food and cover. Acorns provide high energy food during fall and winter and are considered important in the diet of wild turkey, white-tailed deer, squirrels, and many other rodents. When acorns are available animals fatten quickly, go through the winter in good condition, and are most likely to produce healthy young (7). Leaves are used for nest building by birds, squirrels, and raccoons (11). Cavities provide nests and dens for various birds and mammals.

Considered a beautiful shade tree for parks, post oak is often used in urban forestry. It is also planted for soil stabilization on dry, sloping, stony sites where few other trees will grow. It develops an attractive crown with strong horizontal branches. Large trees are difficult to transplant and do not tolerate compaction or removal of soil in developments (19).

The wood of post oak, commercially called white oak, is classified as moderately to very resistant to decay (16). It is used for railroad ties, lathing, siding, planks, construction timbers, mine timbers, trim molding, stair risers and treads, flooring (its highest volume finished products), fenceposts, pulp, veneer, particle boards, and fuel. The bark provides tannin, decorative and protective mulch in landscaping, and fuel.

The tannin in oak leaves, buds, and acorns is toxic to cattle, sheep, and goats. Oak poisoning is a problem in the Southwest where annual livestock losses costing more than $10 million have been estimated. Poisoning occurs more frequently in drought years when other forage is in short supply. The most dangerous season is during the sprouting of new foliage, a period of about 4 weeks in March and April (9).

Post oaks up to 25 cm (10 in) in d.b.h. sprout prolifically after being cut or burned. Along the southwestern margins of its range, post oak spreads rapidly into former grasslands after periodic prairie fires were stopped, and much of this extension appears to be of sprout origin. In one study in which potted seedlings were deprived of moisture until the aboveground parts died, two to three times as many post oaks sprouted after normal moisture was restored than did white, blackjack, northern red, or scarlet oaks (12).

In a comparison of the sprouting habits of five oaks, post oak had more one-stem clumps and fewer sprouts per clump on the average than did black oak, chestnut oak, white oak, or scarlet oak. This characteristic would be important in culture by coppice except that post oak grows more slowly than the others.

Fagaceae -- Beech family

John J. Stransky

Post oak (Quercus stellata), sometimes called iron oak, is a medium-sized tree abundant throughout the Southeastern and South Central United States where it forms pure stands in the prairie transition area. This slow-growing oak typically occupies rocky or sandy ridges and dry woodlands with a variety of soils and is considered drought resistant. The wood is very durable in contact with soil and used widely for fenceposts, hence, the name. Due to varying leaf shapes and acorn sizes, several varieties of post oak have been recognized-sand post oak (Q. stellata var. margaretta (Ashe) Sarg.), and Delta post oak (Quercus stellata var. paludosa Sarg.) are included here.

The range of post oak extends from southeastern Massachusetts, Rhode Island, southern Connecticut and extreme southeastern New York (including Long Island); west to southeastern Pennsylvania and West Virginia, central Ohio, southern Indiana, central Illinois, southeastern Iowa and Missouri; south to eastern Kansas, western Oklahoma, northwestern and central Texas; and east to central Florida (10).

It is a large and abundant tree in the southern Coastal Plain, the Piedmont, and the lower slopes of the Appalachians. It is common in the southwest and grows in pure stands in the prairie transition region of central Oklahoma and Texas known as the "Cross Timbers" (2).

Sand post oak (Quercus stellata var. margaretta (Ashe) Sarg.) ranges from southeastern Virginia, west to Missouri and eastern Oklahoma, south to central Texas, and east to central Florida. Delta post oak (Q. stellata var. paludosa Sarg.) is found in bottom lands of the Mississippi River in western Mississippi, southeast Arkansas, and Louisiana, and west to east Texas (10).


-The native range of post oak.

Quercus stellata, the post oak or iron oak, is a North American species of oak in the white oak section. It is a slow-growing oak that lives in dry areas on the edges of fields, tops of ridges also grows in poor soils, and is resistant to rot, fire, and drought. Interbreeding occurs among white oaks, thus many hybrid species combinations occur.

The species is native to the eastern and central United States, and found along the east coast from Massachusetts to Florida, and as far inland as Nebraska. It is identifiable by the rounded cross-like shape formed by the leaf lobes and hairy underside of the leaves.