White Ash
Fraxinus americana
Olive family (Oleaceae)
Description:
This
tree is 50-100' tall at maturity, forming a long stout
trunk and a
variable crown: in open areas, the crown is ovoid, in forested areas
the crown is more narrow and slightly pyramidal. The trunk bark is
light to dark gray and deeply furrowed, forming interweaving
diamond-shaped patterns; the thick ridges are flat-topped. Bark of
branches and twigs are gray to grayish brown and smooth; young twigs
often have a whitish bloom. Lichens are often abundant on the bark of
the trunk and larger branches. Young shoots are green, terete, and
usually hairless. Pairs of opposite compound leaves develop along these
shoots. Individual leaves are 8-15" long and odd-pinnate with 5-9
leaflets (usually there are 7 leaflets). The petiole and rachis of each
compound leaf are light green and usually hairless. The petiole scars
on the twigs are shaped like the letter 'U' or a narrow crescent moon.
Individual leaflets
are 2½-5" long and about one-half as much across; they are elliptic,
lanceolate-ovate, or ovate with margins that are smooth to slightly
serrated. Each leaflet has a short petiolule (basal stalklet). The
upper leaflet surface is medium green and hairless, while the lower
surface is pale green to whitish green and usually hairless. Trees with
pubescent shoots, petioles, rachises, and leaflet lower sides can be
referred to as Fraxinus
americana biltmoreana (Biltmore Ash), while the
more common typical variety is hairless. The flowers bloom
during the
spring before the leaves develop. Because White Ash is dioecious,
individual trees have either all male (staminate) flowers or all female
(pistillate) flowers. Male flowers occur in tight clusters along
2nd-year twigs. Individual male flowers are less than 1/8" (3 mm.)
across,
consisting of a tiny tubular calyx and 2 stamens. They vary in color
from yellowish green to greenish purple. Female flowers occur in small
panicles on 2nd-year twigs. They are less than 1/8" (3 mm.) across,
consisting
of a tiny tubular calyx and a pistil with a single style. Neither male
flowers nor female flowers have corollas. The flowers are
cross-pollinated by the wind.
Afterwards, male flowers soon wither
away, while fertile female flowers are transformed into one-seeded
samaras, which hang from drooping panicles. Individual samaras are
about 1½" long, consisting of a seed body and elongated membranous
wing. The seed body is more round in cross-section than
flattened, while the
narrow membranous wing does not extend much beyond the lateral margins
of the
seed body. Immature samaras are green to reddish green, while mature
samaras are light to dark brown. They usually remain on the tree into
the fall or winter before being distributed by the wind. The woody root
system is moderately deep and spreads widely; it usually has both a
taproot and major lateral roots. The deciduous leaves become reddish
purple or yellow during the fall."
Cultivation:
White Ash prefers partial to full sun, moist to dry-mesic conditions,
and a
deep loamy soil that is high in nitrogen and calcium. Small saplings
can tolerate more shade than mature trees. This tree is vulnerable to
the disease complex, Ash Yellows, which is potentially fatal. It is
also somewhat sensitive to ozone, sulfur dioxide, and other forms of air pollution.
Range
& Habitat: The native White Ash is
fairly common in most areas of Illinois, except the NW section of the
state, where it is occasional (see Distribution
Map). Habitats include
floodplain woodlands (in better-drained areas), upland woodlands, edges
of shaded gravelly seeps, high riverbanks, limestone glades, and
city parks. This tree can be found in both disturbed wooded areas and
old-growth deciduous forests. Sometimes White Ash is cultivated as a
landscape tree.
Faunal
Associations: White Ash and other native Fraxinus spp.
(ashes)
are host plants of many species of insects, which feed on the leaves,
wood, and other parts of these trees. The caterpillars of Papilio glaucus
(Tiger Swallowtail) sometimes feed on the leaves; the
caterpillars of Ennomos
magnaria (Notched-Winged Geometer), Sphinx chersis
(Great Ash Sphinx), and other moths also feed on the leaves and
other parts of ashes (see Moth Table. The
larvae of several
long-horned beetles (Cerambycidae), metallic wood-boring beetles
(Buprestidae), and bark beetles (Scolytidae) bore through the
wood or bark (see Wood-Boring Beetle Table).
One wood-boring species,
Agrilus planipennis (Emerald Ash Borer), which has been
accidentally introduced from abroad into the
Midwest, is usually fatal to the native ash trees that it
infests. Other insect feeders include the leaf beetles Capraita circumdata
and Trichaltica
scabricula,
the larvae of Tethida
barda (Black-Headed
Ash Sawfly) and Tomostethus
multicinctus (Brown-Headed Ash Sawfly), Lepidosaphes ulmi
(Oystershell
Scale) and other scale insects, Prociphilus
fraxinifolii (Woolly Ash Aphid), Tropidosteptes
amoenus (Ash Plant Bug) and several other plant bugs
(see Plant Bug Table),
the larvae of Dasineura
fraxinifolia and Dasineura
pellex
(Ash Bullet Gall Midge), and Leptoypha
mutica (Fringetree Lace Bug). Vertebrate animals also make
use of
ash trees. The seeds are eaten by such birds as the Wood Duck, Wild
Turkey, Bobwhite, Cardinal, Pine Grosbeak, Evening Grosbeak, and Purple
Finch. The Fox Squirrel, Red Squirrel, White-Footed Mouse, and Woodland
Deer Mouse also eat the seeds, while the White-Tailed Deer and cattle
browse on leaves and twigs. Because older trees of White Ash often form
cavities, they provide good nesting habitat for various birds and tree
squirrels; this includes such birds as the Red-Bellied Woodpecker,
Red-Headed Woodpecker, Pileated Woodpecker, Wood Duck, White-Breasted
Nuthatch, and various owls.
Photographic
Location: Along a riverbank near Busey Woods in Urbana,
Illinois.
Comments: Because the wood of White Ash is strong,
flexible, and shock-resistant,
it is highly regarded and used in the construction of furniture,
doors, cabinets, veneer, railroad ties, wood paneling on antique cars,
boats, tool handles, baseball bats, archery bows, canoe paddles,
snowshoes, polo sticks, tennis rackets, and other wooden items.
White Ash can be distinguished from another common species, Fraxinus pennsylvanica
(Green Ash or Red Ash) by the shape of its petiole scars
on the twigs (like a narrow crescent moon or letter 'U'), the pale
lower surface of its leaflets, and the structure of its
samaras: the winged membrane of each samara does not extend much
beyond the lateral margins of the seed body. In
contrast, Fraxinus
pennsylvanica (Green Ash or Red Ash) has petiole scars
that are shaped
like a half-circle or wide crescent moon, and the winged membrane of
its samaras extends to at least the middle of the seed body's lateral
margins. Other technical characters, such as the cross-sectional shape
of the twigs and the presence or absence of petiolules, can be used to
distinguish White Ash from other Fraxinus
spp. (ashes) in Illinois.