Swamp Aster
Symphyotrichum puniceum puniceum
Aster family (Asteraceae)

Description: This perennial wildflower is 1–6' tall, branching occasionally along the upper half of its length. The rather stout stems are light green to reddish purple (often the latter), terete to slightly grooved, and evenly covered with stiff spreading hairs. The alternate leaves are up to 6" long and 1" across, becoming gradually smaller along the upper half of each plant; they are narrowly lanceolate to lanceolate with poorly defined remote teeth along their margins. The leaves are yellowish green, medium green, or purple (sometimes the latter color during the fall); they are usually glabrous, except for some hairs along the central veins of their lower sides. Most leaves clasp the stems, although some of the smaller upper leaves are sessile.


The central stem terminates in a panicle of flowerheads; some lateral stems may produce smaller panicles of flowerheads. The branches of each panicle are ascending and usually hairy. Along these branches, there are linear-lanceolate leafy bracts up to 1" long. The outer branches terminate in flowerheads about –1" across, consisting of 30-50 ray florets and a similar number of central disk florets. The petal-like rays are usually lavender, pale blue-violet, or purple (less often white); they are widely spreading and very slender. The tubular disk florets are 5-lobed; they are initially yellow, but later become dull red. At the base of each flowerhead, there are several overlapping bracts that are linear in shape, green, and hairless; they are rather loosely assembled around the base of the flowerhead and slightly spreading. The blooming period occurs from late summer into the fall and lasts about 2 months. Both disk and ray florets are fertile. The florets are replaced by bullet-shaped achenes about 1.5 mm. long that have small tufts of white hair; they are distributed by the wind. The root system is fibrous and short-rhizomatous, sometimes forming a small caudex on older plants.

Cultivation: The preference is full or partial sun and wet to moist conditions. The soil should contain some organic material to retain moisture and it should be reasonably fertile. Sometimes, the leaves become diseased and rather battered in appearance by the end of the year; the lower leaves may turn brown and fall off in response to droughty conditions. The size of individual plants can be highly variable.

Range & Habitat: The native Swamp Aster is occasional in the northern half of Illinois, while in the southern half of the state it is uncommon or absent. Habitats include soggy thickets along streams, open swamps, fens and calcareous seeps, sedge meadows, and other wetlands. Swamp Aster is often found in higher quality wetlands where the native flora is still intact. It is primarily a boreal species that is found around the Great Lakes and other cool areas.

Faunal Associations: The nectar and pollen of the flowerheads attract a wide variety of insects, including honeybees, bumblebees, other miscellaneous bees, various wasps, bee flies and other miscellaneous flies, and various butterflies, skippers, and moths. The oligolectic bees, Andrena asteris and Andrena hirticincta, suck nectar and collect pollen from the flowerheads of Swamp Aster. Other insects feed on the foliage, suck plant juices, bore through the stalks and roots, or gnaw on the flowers and developing seeds of Symphyotrichum spp. (asters). These species include Microrhopala xerene and other leaf beetles, several aphids (mostly Uroleucon spp.), the stinkbug Trichopepla semivittata, the leafhopper Macrosteles quadrilineatus, the plant bug Plagiognathus cuneatus, Poecilocapsus lineatus (Four-Lined Plant Bug), Lygus lineolaris (Tarnished Plant Bug), and the larvae of Calycomyza humeralis (Aster Leafminer Fly). In addition to these insects, a large number of moth caterpillars feed on asters (see the Moth Table for a listing of these species), as do the caterpillars of the butterflies Chlosyne nycteis (Silvery Checkerspot) and Phyciodes tharos (Pearl Crescent). Among vertebrate animals, the Wild Turkey eats the seeds and leaves occasionally, while the White-Tailed Deer and Cottontail Rabbit browse on the foliage.

Photographic Location: A low area along a pond at Weaver Park in Urbana, Illinois.


Comments: Except for Symphyotrichum novae-angliae (New England Aster), Swamp Aster has larger flowerheads than other Symphyotrichum spp. (asters) in Illinois and its flowerheads usually have more rays (about 30-50). It is a pretty hefty plant that is about as tall as New England Aster. This latter species has glandular hairs along its stems and its leaves are less shiny than those of Swamp Aster. Swamp Aster is divided into two varieties or subspecies: the typical variety/subspecies has evenly hairy purple stems, while variety/subspecies firmus (or lucidulous) has light green stems that are either hairless or the hairs are arranged in lines; sometimes the color of the stems is not reliable in making this distinction. The rhizomes of the typical variety/subspecies are supposed to be short, while the rhizomes of variety/subspecies firmus (or lucidulous) are supposed to be long. Some authors (e.g., Mohlenbrock, 2014), divide Swamp Aster into two separate species: Symphyotrichum puniceum and Symphyotrichum firmum. They have a similar distribution and are about equally common in Illinois. The preceding descriptive information and photos apply to Symphyotrichum puniceum puniceum. A scientific synonym of Swamp Aster is Aster puniceus.

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