Description:
This perennial wildflower consists of a rosette of basal leaves during
the spring that spans about 6-12" across. The blades of the basal
leaves are up to 8" long and 6" across; they are cordate to
oval-cordate in shape and crenate-serrate along their margins. The
upper surface of these blades is medium green and hairless to
short-hairy, while the lower surface is pale green and hairy along the
major veins. The petioles of the basal leaves are up to 6" long, light
green, and usually hairy. During the summer, unbranched or sparingly
branched stems with alternate leaves are produced, while the basal
leaves wither away. These stems are light green to pale reddish green,
terete, and variably hairy: usually the lower stems are hairless, while
the upper stems are short-hairy. The blades of alternate leaves are up
to 4" long and 3" across; they are mostly cordate with margins that are
serrate or crenate-serrate. Some of the upper leaf blades may be ovate
in shape. The upper surface of these blades is medium green and
hairless to short-hairy, while the lower surface is pale green and
hairy along the major veins. The petioles of the alternate leaves are
up to 3" long and they are often winged, particularly where the
petioles join the stem.
The upper central stem of each plant (and any
upper lateral stems) terminates in a flat-headed panicle (corymb) of
flowerheads spanning 3-8" across. Individual flowerheads are ½-1¼"
across, consisting of 8-20 ray florets that surround numerous disk
florets. The petal-like corollas of the ray florets are lavender or
white. The tubular corollas of the disk florets are initially
pale
yellow or yellow, but they later become orange-red, dark red, or brown.
The tubular corolla of each disk floret has 5 slightly spreading lobes
at its apex. At the base of each flowerhead, there are numerous floral
bracts (phyllaries) that are arranged in 4-6 series; they are appressed
and overlapping. Individual floral bracts are more or less oblong
in shape and mostly green, except for the narrow white margins along
their sides; they are short-pubescent and occasionally ciliate along
their margins. The tips of these bracts are usually blunt; less often,
they are somewhat pointed. The peduncles and pedicels of the panicle
are light green, relatively stout, and covered with short glandular
hairs. At the base of each branch of the panicle, there is usually a
single leafy bract up to 1½" long
that is broadly oblong or broadly elliptic; these bracts
are sessile.
The blooming period occurs from
late summer to early fall and lasts about 1-1½ months. During the
autumn, both ray and disk florets are replaced by small bullet-shaped
achenes; each achene has a tuft of tawny hairs at its apex. The achenes
are distributed by the wind. The root system is fibrous and
long-rhizomatous; on older plants, a small caudex sometimes develops.
This wildflower often forms clonal colonies by means of the spreading
rhizomes.
Cultivation:
The preference is partial sun to medium
shade, moist to dry-mesic conditions, and soil consisting of rich
loam or sandy loam.
Range
& Habitat: The native Big-Leaved
Aster is found only in the northeast section of Illinois, where it is
rare. This species is more common in areas that lie
to the north or east of the state. Habitats consist of beech-maple
woodlands, sandy oak woodlands, sandy oak savannas, elevated areas
(hummocks) in swamps, stabilized sand dunes where oak trees are
dominant, and woodland borders. Usually, Big-Leaved Aster occupies
high-quality natural areas that are more or less mesic (neither too dry
nor too wet) and relatively little-disturbed by human activities.
Faunal
Associations: The nectar and pollen of the flowers attract
a large
variety of insects, including long-tongued bees, short-tongued bees,
wasps, flies, butterflies, beetles, and plant bugs. An oligolectic
Andrenid bee,
Andrena
hirticincta, has been observed visiting the
flowerheads of Big-Leaved Aster (see Graenicher). Other insects feed on
the foliage and flowers, suck plant juices, or bore through the
stems and roots of this aster and others. Examples of such insect
feeders include caterpillars of the butterflies
Chlosyne nycteis
(Silvery Checkerspot) and
Phyciodes
tharos (Pearl Crescent); also the caterpillars of
Carmenta
corni (Aster Borer Moth),
Cucullia asteroides
(The Asteroid),
Schinia
arcigera (Arcigera Flower
Moth), and other moths feed on asters (see
Moth Table). Other
insects
feeders include the larvae of
Calycomyza
humeralis (Aster Leafminer
Fly), several aphids (mostly
Uroleucon
spp.),
Macrosteles
quadrilineatus (Aster Leafhopper), the lace bugs
Corythucha marmorata
and
Galeata spinifrons,
the leaf beetles
Exema
canadensis and
Ophraella
pilosa, the plant bug
Plagiognathus
cuneatus, and others (see
Insect
Table for a more complete listing of species). Some
vertebrate animals
use asters as a food source. The Ruffed Grouse and Wild Turkey eat the
seeds and foliage, while the White-Tailed Deer and Cottontail Rabbit
sometimes browse on the foliage. The foliage is also
edible to cattle, sheep, and other domesticated farm animals.
Photographic
Location: The
photograph of the basal leaves was taken at a deciduous woodland in NW
Ohio, while the photographs of the flowerheads were taken at a woodland
border and a sandy oak savanna in the Indiana Dunes State
Park, NW Indiana.
Comments:
Sometimes Big-Leaved Aster is referred to as
Aster macrophyllus.
The large basal leaves of this aster are very
conspicuous during the spring. During the autumn, Big-Leaved Aster
resembles many other woodland asters and it is more difficult to
identify. However, it can be distinguished from similar species by the
appearance of its floral bracts (phyllaries), the presence of
short glandular hairs on its peduncles and pedicels (a 10x hand lens
may be required), and the flat-headed characteristic of its panicles.
Most asters have elongated panicles of flowerheads that are not
flat-headed. A species that is not found in Illinois,
Eurybia
divaricata (White Wood Aster), shares this flat-headed
characteristic
with Big-Leaved Aster and its leaves have a similar shape.
However, White Wood Aster has flowerheads with fewer ray florets (about
5-10), its peduncles and pedicels usually have non-glandular hairs,
and its basal leaves are smaller in size.