Aster family (Asteraceae)
Description: This perennial plant is 1-2' tall, branching frequently to create a bushy appearance. The slender stems are rather stiff and slightly pubescent; the lower stems turn brown and become slightly woody during the fall. The alternate leaves are up to 2" long and ½" across, becoming smaller as they ascend the stems; they are typically one-half the maximum size or a little less. They are linear to linear-oblong, slightly pubescent, and smooth along the slightly ciliate margins. These leaves are rather densely crowded along the stems (particularly the upper stems) and sessile.
The compound flowers are daisy-like and about 1–1¼" across. Each compound flower consists of about 20-35 blue-violet or purple ray florets that surround numerous disk florets that are yellow or amber. These disk florets later become reddish purple. Each compound flower is subtended by spreading linear bracts that resemble the upper leaves. The blooming period occurs during the fall and lasts about 1-2 months; a robust plant will be covered with flowerheads. There is no noticeable floral scent, although the crushed foliage and flowerheads have a balsam-like aroma. Aromatic Aster is one of the last wildflowers to bloom prior to heavy frost. The achenes have small tufts of light brown hair and are distributed by the wind. The root system is fibrous and rhizomatous; older plants often have a short caudex. There can be significant variability in the characteristics of plants across different locations.
Cultivation: The preference is full sun and dry conditions, although an average moisture level is tolerated if the site is well-drained. Poor, rocky soil with open terrain is preferred; a high pH is tolerated. Some of the lower leaves may wither away before the plants begin to bloom, but the foliage usually remains quite attractive. At moist fertile sites, this plant has trouble competing against tall aggressive plants, unless such neighbors are selectively weeded out.
Range & Habitat: The native Aromatic Aster occurs primarily in northern Illinois, the hilly sections of southern Illinois, and in areas bordering the Mississippi and Illinois rivers (see Distribution Map). It is generally an uncommon plant, although locally common at a few exceptional sites. Habitats include mesic to dry gravel prairies, dolomite prairies, gravelly hill prairies, limestone glades, and rocky bluffs along major rivers.
Faunal Associations: Many insects visit the flowers, including long-tongued bees, short-tongued bees, small to medium-sized butterflies, and skippers. These insects seek nectar primarily, although the bees also collect pollen. Many kinds of insects feed on the foliage and other parts of asters, including the caterpillars of the butterfly Chlosyne nycteis (Silvery Checkerspot) and many moth species (see Moth Table). The Wild Turkey and possibly other upland gamebirds eat the seeds and foliage to a limited extent. Mammalian herbivores occasionally eat the foliage of asters, even though their food value is low.
Photographic Location: The above photographs were taken in the wildflower garden of the webmaster in Urbana, Illinois.
Comments: This aster has attractive flowers and is fairly easy to cultivate in a sunny rock garden and similar areas. Aromatic Aster can be distinguished from other asters (Symphyotrichum spp.) by the number of ray florets per flowerhead (greater than 20), the size of its flowerheads (usually about 1" across or slightly more), and the spreading linear bracts underneath each flowerhead. The leaves are shorter and more narrow than those of many other Aster spp., and they release a pleasant aroma when crushed. In general habit, Aromatic Aster has denser foliage and a bushier habit than other asters, which are usually more tall and lanky. In mass-market horticulture, some plants that are labeled 'Aromatic Aster' appear to be hybrids of Aromatic Aster and Symphyotrichum novae-angliae (New England Aster). These cultivated plants tend to be larger in size and have larger lower leaves; their flowerheads are slightly larger and more double than those of Aromatic Aster.