Sky Blue Aster
Aster family (Asteraceae)
Description: This native perennial plant is 1½3' tall, and largely unbranched except at the inflorescence. The central stem is light green and largely hairless. Near the base of the plant, are basal leaves with long narrow petioles. These basal leaves are about 3" long and 1½" across, cordate or broadly oval, and largely hairless. Their petioles are about 1½" long and finely pubescent, while their margins are smooth, or nearly so. As the leaves alternate upward along the stem, they become greatly reduced in size and more narrow. These upper leaves are narrowly lanceolate, narrowly elliptical, or linear; they are sessile against the stem.
The inflorescence is a large panicle of compound flowers that are daisy-like in appearance; this large inflorescence has a tendency to droop over somewhat. The compound flowers are about ½" across or slightly larger. They consist of about 10-25 lavender or light blue ray florets, which surround numerous disk florets that are initially yellow, but later turn red or brown. The compound flowers are subtended by numerous bracts that are ciliate and form small green diamonds. The blooming period occurs from late summer to fall, and lasts about 1-2 months. Later, achenes develop with small tufts of hair, which are dispersed by the wind. The root system is fibrous and rhizomatous; older plants may develop a short caudex.
Cultivation: The preference is full or partial sun and mesic to dry conditions. This plant is rather indifferent to soil characteristics, and can flourish in soil that loamy, sandy, rocky, or contains clay. This plant is easy to grow and drought resistant; the lower leaves are occasionally marred by powdery mildew and other foliar diseases.
Range & Habitat: Sky Blue Aster occurs occasionally in the northern and western halves of Illinois, but is uncommon or absent elsewhere (see Distribution Map). Habitats include mesic to dry black soil prairies, rocky upland woods, savannas, woodland borders, sandy meadows, limestone glades, clay banks, and areas along roadsides.
Faunal Associations: The flowers attract various insects, including small bees, flies, small to medium-sized butterflies, skippers, and wasps. Among these, Green Metallic bees and other Halictid bees are especially common visitors of the flowers, where they seek nectar or pollen. The caterpillars of the butterfly Chlosyne nycteis (Silvery Checkerspot) and several species of moth feed on this and other asters (see Moth Table). The Wild Turkey and been observed feeding on the foliage and seeds of asters to a limited extent. Many mammalian herbivores occasionally eat this plant, even though it has low food value, including rabbits, deer, groundhogs, and livestock.
Photographic Location: The photographs were taken at the webmaster's wildflower garden in Urbana, Illinois.
Comments: For the size of the plant, the inflorescence of Sky Blue Aster is rather large and showy. This species of aster closely resembles Aster shortii (Short's Aster), even though the latter is a woodland species. However, the upper leaves of Short's Aster are often cordate, rather than narrowly lanceolate or linear, and its flowers are slightly larger in size. Another similar species, Aster laevis (Smooth Blue Aster), doesn't have any cordate or broadly oval leaves at the base of the plant, unlike Sky Blue Aster, and the flowers of the former species tend to be slightly larger in size as well. In distinguishing the different species of asters, it is often useful to consider the shape of the leaves (especially the basal leaves), and the presence or absence of fine hairs on the foliage and stems. Another scientific name for this plant is Aster azureus.