Aster family (Asteraceae)
Description: This native perennial wildflower is ½–1½' tall, sending up one or more unbranched leafy stems from the root system. These stems are erect, ascending, or sprawling; they are light green, tan, or reddish brown, terete, and canescent. Along each stem, there are densely spaced alternate leaves that appear to be whorled (pointing in all directions). Individual leaves are ¾–1½" long and 1/8" across; they are linear in shape, smooth along their margins, stiff, and sessile (or nearly so). The upper surfaces of the leaves are medium to dark green and glabrous, while their lower surfaces are pale green and canescent. Each leaf has a prominent midvein.
The central stem terminates in a small cluster of flowerheads (sometimes only a single flowerhead is produced, but there are usually more). Individual flowerheads are born on unbranched peduncles about ½–2" long (rarely, they are longer). Along each peduncle, there are small bracts up to ¼" long that resemble the leaves, except they are much smaller in size. The daisy-like flowerheads span ¾–1¼" across, consisting of 10-20 ray florets and a similar number of disk florets. The petal-like rays are lavender or pale blue-violet, while the tiny corollas of the disk florets are bright yellow, later becoming orange-red. At the base of each flowerhead, there are 4-5 series of appressed floral bracts. Individual floral bracts are scale-like in appearance and linear-oblong in shape; each of these bracts is medium green along the upper one-half of its length, otherwise it is nearly white. The blooming period occurs from early to mid-fall and lasts about 1 month. Both disk and ray florets produce achenes. The small achenes are bullet-shaped and pubescent; there is a small tuft of hairs at the apex of each achene. For each tuft, the spreading inner hairs are long, while the outer hairs are short. The tufted achenes are distributed by the wind. The root system forms a caudex with fibrous roots; sometimes, spreading rhizomes are produced, from which vegetative offsets can develop.
Cultivation: The preference is full or partial sun, dry-mesic conditions, and an acidic soil that is sandy or rocky. This wildflower can be cultivated in rock gardens.
Range & Habitat: Flax-Leaved Aster is occasional in the northern half of Illinois, while in the southern half of the state it is rare or absent (see Distribution Map). Habitats include upland sand prairies, upland sandy savannas, stabilized sand dunes, open rocky woodlands, rocky wooded slopes, and sandstone glades. This wildflower is found in high quality natural habitats with sparse ground cover. It benefits from occasional wildfires in wooded areas, as this reduces the encroachment of woody vegetation.
Faunal Associations: The nectar and pollen of the flowerheads attract many kinds of insects, including long-tongued bees, short-tongued bees, various flies, butterflies, skippers, and beetles. Several bees are pollinator specialists (oligoleges) of Aster spp. (Asters): Andrena asteris, Andrena asteroides, Andrena hirticincta, Andrena nubecula, Andrena simplex, Andrena solidaginis, and Colletes simulans armata. Some of these bees are also oligoleges of Solidago spp. (Goldenrods). Other insects feed on the leaves, flowers, seeds, plant juices, stalks, or roots of Asters. These species include the plant bug Plagiognathus cuneatus, the leafhopper Macrosteles quadrilineatus, Exema canadensis and other leaf beetles, the long-horned beetle Mecas pergrata, several aphids (mainly Uroleucon spp.), and caterpillars of the butterflies Chlosyne nycteis (Silvery Checkerspot) and Phyciodes tharos (Pearl Crescent). There are also many moth species whose caterpillars feed on Asters (see Moth Table). Among vertebrate animals, the Ruffed Grouse and Wild Turkey eat the leaves and seeds, while the Cottontail Rabbit and White-Tailed Deer browse on the foliage. The White-Footed Mouse and possibly other small rodents also eat the seeds.
Photographic Location: An upland sandy savanna at Hooper Branch Savanna Nature Preserve in Iroquois County, Illinois.
Comments: This wildflower has an elegant appearance. What distinguishes Flax-Leaved Aster from species in the Aster genus are the tufted hairs of its achenes: they consist of a combination of long and short hairs, rather than hairs of uniform length. Nonetheless, it is sometimes referred to as Aster linariifolius because of its similarity to these species in other respects. Flax-Leaved Aster superficially resembles Aster oblongifolius (Aromatic Aster) to some extent, but it has unbranched stems, while the latter species has abundantly branched stems. Because of its short linear leaves, which are arranged in dense pseudo-whorls, Flax-Leaved Aster is relatively easy to identify. Another common name of this species is Stiff-Leaved Aster.