Description:
This small single-trunked tree is typically 10–30' tall in the wild,
although in cultivation it may become 30–50' tall. The crown of this
tree is usually as broad as it is across in open areas and densely
branched, while in more shaded areas the crown becomes more open and
elongated. However, small trees that are stunted from rocky barren
ground often have a crown that is irregularly shaped and open. The
trunk is up to 1' across and short; it is covered with nearly black
coarse bark that is irregularly furrowed or blocky. The smaller
branches and older twigs are more gray and smooth; they tend to be
short and craggy. Young twigs are light brown with short brown
pubescence toward their tips; the conical or bluntly conical buds are
also light brown with short brown pubescence.
Alternate leaves
occur along young twigs; they are 3–7" long, 2½–6" across, and obovate
or obovate-obconic in outline with 3–5 shallow lobes along their
outer margins. The lobes of the leaves taper to tips that are obtusely
angled,
shallowly rounded, or bluntly square-shaped; each lobe has an exserted
vein. The leaf base is narrowly rounded to wedge-shaped, while the leaf
margins are
irregularly undulate or slightly curved where the shallow lobes don't
occur. The upper leaf surface is dark green, shiny, and sparsely
covered with short brown pubescence that is stellate (star-shaped). The
lower leaf surface is light-medium green, dull, and moderately covered
with short brown pubescence that is stellate. Such brownish pubescence
is especially common along the lower sides of leaf veins. The petioles
are 3–12 mm. (up to ½") long; they are greenish white or pale yellow,
and glabrous or with short brown pubescence. Like other oaks, this oak
is monoecious with male (staminate) and female (pistillate) florets
occurring on the same tree. The male florets are distributed along
drooping greenish
yellow catkins up to 5" long; each male floret (less than 3 mm. in
size) has about 6 stamens, a short calyx with 4-6 lobes, and
early-deciduous bractlets. The
female florets are nearly sessile on the twigs; each female floret
(less than 3 mm. in size) consists of an ovary with 2-3 styles,
a calyx with 4-6 lobes, and several surrounding bractlets.
The blooming
period occurs from mid- to late-spring, lasting about 1–2 weeks.
Cross-pollination of the florets is by wind. Afterwards, fertile female
florets slowly develop into nearly sessile acorns that are solitary or
in clusters of 2–3. These acorns take 2 years to develop and they don't
become mature until autumn of the following year. Individual acorns are
about ¾" long and ½" across, consisting of a rather deep cup with light
brown pubescent scales and an ovoid nut that is smooth-sided, light
to medium brown, and pointed at its apex. The cup extends along
one-third to one-half of the
length of the acorn and partially overlaps the nut. The interior of the
nut is nearly white, meaty, and somewhat bitter. The woody root system
of this
tree produces a deep taproot with more shallow lateral roots. This tree
reproduces by reseeding itself. During autumn, the leaves become dull
yellow to red before turning brown; they have a tendency to persist on
this tree during the winter.
Cultivation:
The
preference is full
sun, dry-mesic to dry conditions, and barren ground containing sand,
gravel, clay, and/or rocky material. This tree grows slowly and can
live up to 200 years.
Range
&
Habitat: Blackjack Oak (Quercus marilandica) is
native to southern and west-central Illinois, where it is occasional
(see
Distribution
Map).
Elsewhere within the state, it does not occur as a wild tree. Illinois
lies along the northern range-limit of this tree; it occurs primarily
in the southeast and southern plains area of the USA. Habitats include
upland rocky woodlands, rocky outcrops, thinly wooded bluffs, upland
sandy woodlands, upland sandy savannas, sandstone glades, limestone
glades, shale glades, edges of sandy prairies, and abandoned fields.
Blackjack Oak typically occurs in drier areas of oak-hickory woodlands
and savannas; in sandy areas of Illinois, it often occurs with Black
Oak (Quercus velutina). Blackjack Oak is often top-killed by
wildfires, but it can resprout from its roots. In Illinois, it is
usually found in higher quality natural areas.
Faunal
Associations: Like other oaks, Blackjack Oak (Quercus
marilandica) is a
food plant of many insects. Examples of insects that are known to feed
on this oak include leaf beetles (Metachroma laevicolle, Xanthonia
striata), nut-feeding larvae of weevils (Curculio humeralis, Curculio
longidens), aphids (Myzocallis punctatus), armored scales (Melanapis
obscura), leaf-mining larvae of moths (Nepticula quercipulchella), and
leafhoppers (Eratoneura spp.). In particular, Blackjack Oak is a
preferred host plant of the leafhoppers
Eratoneura havana,
Eratoneura
marilandicae, and
Eratoneura
tenuitas (Clark et al., 2004; Gibson,
1985; Hottes & Frison, 1931; ScaleNet, 2014; Needham et al.,
1928;
Dmitriev & Dietrich, 2010). Other insects that feed on this and
other oaks include the larvae of wood-boring beetles (Buprestidae,
Cerambycidae), the larvae of bark beetles (Scolytidae), treehoppers
(Membracidae), the larvae of sawflies (Tenthredinidae), the larvae of
skippers (Hesperiidae), the larvae of Hairstreak butterflies
(Lycaenidae), walkingsticks (Diapheromeridae, Pseudophasmatidae), and
the larvae of hundreds of moths (Geometridae, Noctuidae, Saturniidae,
etc.).
Among vertebrate animals, the relatively small acorns of this
tree are eaten by such birds as the American Crow, Blue Jay, Tufted
Titmouse, Bobwhite Quail, Wild Turkey, Greater Prairie Chicken,
Ring-necked Pheasant, Red-headed Woodpecker, Red-bellied Woodpecker,
and Passenger Pigeon (now extinct). Mammals that feed on the acorns
include the Gray Fox, American Black Bear, White-tailed Deer, Raccoon,
Eastern Gray Squirrel, Fox Squirrel, Prairie Vole, and White-footed
Mouse (DeGraaf, 2002; Martin et al., 1951/1961). This small tree
provides good cover for birds, mammals, and other wildlife.
Photographic
Location: A sandy savanna and edge of an upland sand
prairie at the
Sand Prairie & Scrub Oak Nature Preserve in Mason County,
Illinois.
Comments:
With the exception of the Dwarf Chinkapin Oak (Quercus prinoides), this
is the smallest oak in Illinois. Blackjack Oak is rarely cultivated,
but it is able to adapt to harsh dry environments of various kinds.
This oak can be easily identified by its small size, the unusual shape
to its leaves, and the short brown pubescence on its young twigs and
leaves (especially the undersides of the latter). This oak is known to
hybridize with many other oaks species in the Red Oak/Black Oak group,
and such hybrids are common, causing irregularities in the shape of its
leaves. The purest strain of Blackjack Oak has leaves with only 3-5
lobes and those lobes are obtusely pointed, rather than rounded. When
this oak hybridizes with other oaks, such as Post Oak (Quercus
stellata) or Black Oak (Quercus velutina), the leaves will have more
rounded and abundant lobes. The photograph of the leaves for the hybrid
Bush's Oak (Quercus marilandica × Quercus velutina, Quercus × bushii)
shows what such leaves look like.