Description: This native perennial plant is 2-3½' tall and little branched, except near the inflorescence. It is initially erect, but often leans over as a result of the heavy inflorescence. The stems are usually green with lines of white hairs; sometimes they are dull purplish red. The alternate leaves are up to 3½" long and 2" across, becoming smaller as they ascend the stems. These leaves are cordate in shape and serrate along the margins. Their petioles are up to 1" long and conspicuously winged. The upper surface of these leaves is nearly hairless or covered with sparse short hairs, while the lower surface is glabrous, except for a few hairs along the major veins.
The upper stems terminate in large
panicles of compound flowers. These panicles are usually longer than they are
wide; they are pyramidal or oblong, rather than flat-topped. Each compound
flower is up to ½" across, consisting of about 8-18 lavender or light
blue ray florets and a similar number of disk florets. The disk florets are
initially cream or light yellow, but become reddish purple with maturity. The
floral bracts are narrowly lanceolate, appressed together or slightly
spreading, and have dark green tips that are more or less diamond-shaped.
Sometimes the tips of the floral bracts assume a reddish tint in bright
sunlight. The blooming period occurs from late summer to the fall and lasts
about 2 months. The achenes have small tufts of hair and are distributed by the
wind. The root system consists of a caudex and rhizomes. This plants spreads
vegetatively and by reseeding itself.
Cultivation: The preference is partial sun and
average to dry conditions. Soil that is loamy or slightly rocky is acceptable.
The leaves have a tendency to become ragged-looking and turn yellowish green
when they are exposed to bright sunlight. Sometimes powdery mildew attacks the
leaves during the late summer or fall.
Range &
Habitat: The Arrow-Leaved Aster is common in most areas of Illinois,
except some counties in the south central area of the state. Habitats include
open upland woodlands, particularly where old oaks occur, woodland edges,
savannas, rocky glades, and meadows in woodland areas. It tolerates disturbance
to some extent.
Faunal Associations:
The compound flowers attract many kinds of insects, including long-tongued
bees, short-tongued bees, Syrphid flies, bee flies, and occasionally
butterflies or skippers. The caterpillars of the butterfly Chlosyne
nycteis (Silvery Checkerspot) feeds on the foliage of aster, as do the
caterpillars of several species of moths. The Wild Turkey eats the seeds and
young foliage to a limited extent. Various mammalian herbivores occasionally
eat the foliage of both immature and mature plants, including deer, rabbits,
groundhogs, and livestock.
Photographic
Location: Crystal Lake Park in Urbana, Illinois, where this species
is rather common.
Comments: The
Arrow-Leaved Aster is one of many woodland asters with light blue flowers. The
leaves are sometimes rather coarse, but the large panicles of flowers are
showy. This species has a similar appearance to Aster drummondii
(Drummond's Aster) and Aster cordifolius (Blue Wood Aster), which occur
in similar habitats. Drummond's Aster has stems and leaves that are evenly
pubescent, while the Arrow-Leaved Aster has lines of hairs on its stems and its
leaves are sparsely hairly or nearly glabrous; otherwise, these two species are
nearly identical to each other. The Blue Wood Aster has leaves with slender
petioles, while the Arrow-Leaved Aster has leaves with petioles that are
conspicuously winged. Sometimes the latter is assigned the scientific name
Aster cordifolius sagittifolius.