Sky-blue aster has blue, daisylike flower heads with yellow to reddish centers in clusters above arrowhead-shaped foliage. These 2- to 3-foot-tall perennials bloom from late summer to mid-fall. They are successful in rock gardens, native gardens, cottage gardens, beds, and borders with full sun and moist to dry soils. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region and current research.
Size and method of spreading:
At maturity, sky-blue aster reaches 2 to 3 feet tall and 1 ½ to 2 feet wide. The plants form clumps by producing offsets from underground stem structures (rhizomes) and by self-seeding.
Native geographic location and habitat: (include C-value if appropriate)
The native range of sky-blue aster includes the Eastern and Central United States. C Value: 8.
Attracts birds or pollinators:
Sky-blue aster flowers attract various bee species, beetles, butterflies, and skippers. The seeds are eaten by birds such as the ruffed grouse, tree sparrow, and wild turkey.
Leaf description:
The leaves of sky-blue aster occur around the base of the plant (basal leaves) and alternate up the stems. The basal leaves and the leaves on the lower portions of the stems are shaped like arrowheads (cuneate). As they ascend the stem, the leaves will be reduced in size and the stalks (petioles) will shorten. The uppermost leaves can be stalkless (sessile). Narrow margins, or wings, are present near the tips of the petioles. Both the upper and lower surfaces of the leaves are covered with short, stiff hairs (pubescent) that give the leaves a rough texture. The edges of the leaves are smooth (entire) or have very small teeth spaced widely apart (serrate).
Flower description:
Sky-blue aster flower heads are daisylike composites of 10 to 25 blue, petallike ray flowers and a center of 15 to 28 yellow disk flowers that mature to a reddish color. These composite flower heads are between one-half to three-quarters of an inch in diameter and occur in branched clusters (panicles) at the terminal ends of the upper stems. Surrounding the bases of the flower heads are four to six layers of diamond-shaped, leaflike structures (bracts) that are mostly green with purple tips.
Fruit description:
The fruit of sky-blue asters resembles dandelion fruit, with a small, dry fruit (achenes) that has long tufts of hair on the tips.
Plant Care:
Maintaining good air circulation can reduce foliar issues with powdery mildew. Deadheading spent flower heads can help reduce self-seeding.
List of pests, diseases, and tolerances:
Sky-blue aster is prone to issues with powdery mildew. Some pests that can cause damage to sky-blue aster plants include aphids, larvae of aster borer moth and other moths, larvae of aster leafminer fly, aster leafhopper, Blatchley’s walking stick, butterfly larvae, fruit fly larvae, goldenrod lace bug, grasshoppers, mealybugs, larvae of papery blister gall midge, plant bugs, and the larvae of tumbling flower beetles. Mammalian herbivores such as deer and rabbits forage for the foliage of sky-blue aster. This species is tolerant of rocky, sandy, or clay soils as long as they are well-drained. The species is also tolerant of drought and dry soils.
