Description: This
native perennial plant is 2-5' tall, branching occasionally. The larger stems
are occasionally reddish, and have lines of white hairs. The alternate leaves
are up to 5½" long and ¾" across, becoming smaller and narrower
as they ascend up the stems. They are lanceolate, narrowly ovate, or linear,
and have smooth margins. Underneath, the leaves are whitish green with a
reticulate network of fine veins that is quite conspicuous. The inflorescence
is large and pyramidal, containing numerous daisy-like composite flowers from
½–1" across. Each flower has 20-30 lavender or light blue ray
florets surrounding numerous yellow disk florets that eventually become reddish
purple. The blooming period occurs from early to mid-fall, and lasts about a
month. There is no noticeable floral scent. The achenes develop with small
tufts of hair, and are dispersed by the wind. The root system is fibrous and
rhizomatous. The Willow Aster often spreads vegetatively to form small to large
colonies.
Cultivation: The
preference is full sun, moist conditions, and fertile loamy soil. Foliar
disease occurs occasionally, which may involve some yellowing of the leaves and
the formation of black spots. This affects primarily the older leaves near the
base of the plant, otherwise the foliage remains attractive. Some standing
water is tolerated if it is temporary.
Range
& Habitat: Willow Aster is widely distributed and occurs in most
counties in Illinois (see
Distribution
Map). It is occasional to locally common. Habitats include moist black soil
prairies, moist meadows along rivers and lakes, thickets, roadside ditches,
abandoned fields, and other poorly drained areas.
Faunal Associations: Many kinds of insects visit the
flowers, including long-tongued bees, short-tongued bees, flies, butterflies,
and skippers. Among the bees, this includes such visitors as honeybees,
bumblebees, Halictine bees, and some Andrenid bees that fly late in the season.
Some Syrphid flies and beetles may feed on the pollen, otherwise these insects
seek nectar; bees also collect pollen for their larvae. The caterpillars of the
butterflies Chlosyne nycteis (Silvery Checkerspot) Phyciodes
tharos (Pearl Crescent) feed on the foliage, as well as the caterpillars of
several species of moths (see
Moth Table). Various insects suck the
juices from this and other asters, including plant bugs, lace bugs, and aphids.
The Wild Turkey eats the foliage and seeds to a limited extent. Deer browse on
this plant occasionally, while rabbits nibble on the foliage of immature
plants.
Photographic
Location: The photographs were taken at Loda Cemetery Prairie in
Iroquois County, Illinois. The lower photograph reveals the underside of the
leaves.
Comments: This is another
attractive aster for autumn bloom, producing abundant flowers. The Willow Aster
can be distinguished from other asters by the conspicuous reticulated pattern
on the lower surface of the leaves. Unlike many woodland asters, the leaves are
always narrow and willow-like, even at the base of the plant, and they lack
serrated edges. The flowers are usually lavender or light blue; sometimes they
are white.