Description:
This tree becomes 50-80' tall at maturity, forming a long straight
trunk up to 3' across and an open crown with ascending branches.
Trunk bark is orange-tinted white to gray and relatively smooth,
although the trunk bark of old trees is more furrowed, rough-textured,
and gray-brown. Branch bark is gray to nearly white and smooth, while
twigs
are light gray to orange-brown and glabrous. Alternate
deciduous leaves about 3-4" long and 2-3½" across occur along the twigs
and young shoots; they are oval in shape and coarsely crenate-dentate
along their margins. There are typically 5-15 large teeth with blunt
tips on each side of the leaf. The upper leaf surface is medium green
and glabrous, while the lower leaf surface is light to medium green and
glabrous to sparsely pubescent. However, young leaves, as they emerge
during the spring, are densely covered with white silky hairs; these
hairs soon fade away as the season progresses. The flattened petioles
are 2-4" long, light green or grayish green, and glabrous to pubescent.
Big-Tooth Aspen is dioecious, developing male (staminate) and female
(pistillate) flowers on separate trees. Male flowers are produced in
drooping catkins about 2-4" long. Each male flower
(about 1/8" or 3 mm. across) has a short disk at its base with about 12
stamens;
each male flower is also accompanied by a bract that is deeply cleft
into narrow ciliate lobes. Female flowers are produced in spreading or
drooping catkins about 1½-3" long. Each female flower (about 1/8" or 3
mm.
across) has a short disk at its base and a conic-lanceoloid ovary. At
the apex of each ovary, there is a pair of stigmata; each stigma is
deeply bifurcated. Each female flower is accompanied by a bract that is
deeply cleft into narrow ciliate lobes. The blooming period occurs
during
mid-spring for 1-2 weeks; the flowers are cross-pollinated by the wind.
Afterwards, the female catkins become slightly longer and the female
flowers are replaced by conic-lanceoloid seed capsules up to ¼" long.
Each of these capsules divides into 2 parts to release several tiny
seeds
that are embedded in tufts of fine white hair. The seeds are
distributed by the wind. The woody root system is shallow and widely
spreading; it often forms clonal trees from underground runners. The
leaves of immature clonal trees tend to be larger in size and less
prominently toothed than those of a mature tree. The deciduous leaves
become pale yellow during the autumn.
Cultivation:
The preference is full sun, moist well-drained conditions, and sandy
loam. However, partial sun, drier conditions, and other soil types are
also tolerated. This tree develops quickly and may live up to 100
years. In some situations, it can spread aggressively by developing
clonal trees from underground runners.
Range
& Habitat:
The native Big-Tooth Aspen occurs occasionally in northern and
east-central
Illinois; elsewhere in the state, it is uncommon or absent. Illinois
lies along the southern range-limit for
this species. Habitats consist of upland woodlands and sandy
woodlands, typical savannas and sandy savannas, disturbed open
woodlands, riverbanks, and abandoned fields. Big-Toothed Aspen is a
pioneer species that prefers disturbed areas that are not too
shady. Mature trees are easily damaged by wildfires because of their
thin bark. Nonetheless, Big-Toothed Aspen can rapidly spread after a
wildfire because clonal trees soon develop from underground
runners.
Faunal
Associations: Big-Toothed Aspen and other
Populus spp. are
hosts to
many kinds of insects. The foliage of these trees is eaten
by caterpillars of the skipper
Erynnis
icelus
(Dreamy Duskywing)
and caterpillars of the butterflies
Limenitis archippus
(Viceroy),
Limenitis arthemis
arthemis (White Admiral),
Limenitis arthemis
astyanax (Red-Spotted Purple), and
Nymphalis vau-album j-album
(Compton
Tortoiseshell). The caterpillars of
Protitame virginalis
(Virgin Moth)
and other moths also feed on these trees (see
Moth Table). Other
insect
feeders include larvae of the sawfly
Trichosoma triangulum,
the leafhoppers
Idiocerus
lunatus and
Kybos
copula, the
plant bug
Tropidosteptes
populi,
Aphis
maculatae (Spotted Poplar Aphid),
Chaitophorus
populifolii (Poplar
Leaf Aphid),
Pterocomma
smithiae (Black Willow Aphid), and
Thecabius
populiconduplifolius (Folded-Leaf Poplar Aphid). The
larvae of several
long-horned beetles bore through the wood of these trees; these species
include
Anoplophora
glabripennis (Asian Long-Horned Beetle),
Oberea
delongi (Poplar-Twig Borer),
Oberea schaumi
(Poplar-Branch Borer),
Saperda calcarata
(Poplar Borer),
and
Saperda
inornata (Poplar-Gall
Saperda). The following leaf beetles have been
observed to feed on
Big-Toothed Aspen:
Chrysomela
crotchi,
Chrysomela
knabi,
Chrysomela
laurentia,
Chrysomela
lineatopunctata,
Chrysomela
scripta,
Crepidodera
populivora,
Crepidodera
solita,
Phratora
purpurea,
Tricholochmaea
decora, and
Zeugophora
scutellaris (see Clark
et al., 2004). Among vertebrate animals, the Ruffed Grouse and Greater
Prairie Chicken feed on the buds and catkins; the buds are also eaten
by the Purple Finch, Fox Squirrel, and Red Squirrel. Twigs and foliage
are a source of food for White-Tailed Deer and Elk; the Cottontail
Rabbit and Meadow Vole gnaw on the bark of saplings and young clonal
sprouts during the winter. When Big-Toothed Aspen grows along rivers,
its bark and wood are a source of food to the Beaver, while its
branches are used as construction material for the lodges and dams of
this animal. As this tree becomes older, it often forms cavities that
are used as nesting habitat by the Red-Breasted Nuthatch, owls, and
woodpeckers, while other birds nest along its branches. Tree squirrels
and other mammals also use the cavities as dens.
Photographic
Location: A deciduous woodland in Fayette County,
Illinois. The
photographs were taken by Keith & Patty Horn (Copyright © 2010).
Comments:
Big-Toothed Aspen is similar to Quaking Aspen (
Populus tremuloides),
except the latter has slightly smaller leaves (2-3" long) with more
abundant smaller teeth (about 25 per side). It also resembles the more
common Eastern Cottonwood (
Populus
deltoides), except the latter has
leaves with truncate bottoms and more abundant smaller teeth. All three
of these species have leaves with flattened petioles, which causes them
to flutter in response to even a weak breeze. With the exception of the
introduced
Populus
nigra italica (Lombardy Poplar), other
Populus spp. in
Illinois
have leaves with round petioles. Occasionally, Big-Toothed Aspen and
Quaking Aspen hybridize, which has been named
Populus × smithii.
This hybrid tends to have leaves with more teeth than those of
Big-Toothed Aspen, but fewer teeth than those of Quaking Aspen.