Aster family (Asteraceae)
Description: This native annual plant is 2-8' tall and little branched, except at the top near the inflorescence. The central stem is round and largely hairless, with fine vertical lines that are dark green. The alternate leaves are up to 8" long and 3" across. They are lanceolate, ovate, or oblanceolate, often with pinnate lobes. The upper surface of the leaves is glabrous or has scattered white hairs, while the margins are coarsely serrated or dentate. The lower leaves have short petioles, while the smaller upper leaves are sessile.
The upper stems terminate in panicles of flowerheads. A flowerhead consists of numerous tubular disk florets, which are enclosed by green bracts that are smooth and linear. Sometimes these bracts assume a purplish appearance. The corollas of the disk florets, which are barely visible above the bracts, are white. The outer florets are fertile and pistillate, while the inner florets are hermaphroditic or sterile. The flowerheads are about ¾" long and ¼" across; they are slightly wider at the base, where there may be some outer bracts that are very short and linear. The blooming period occurs during late summer or early fall for about a month. There is no floral scent, although the foliage has a rank smell. The achenes develop with tufts of soft white hair; they are dispersed by the wind. The root system is shallow and fibrous.
Cultivation: The preference is light shade to full sun, and moist conditions. The size of a plant can vary considerably depending on the fertility of the soil and the amount of available moisture. The soil should have sufficient organic material to retain moisture; some gravelly material is apparently acceptable as this plant often grows along railroad tracks.
Range & Habitat: Pilewort occurs in most counties of Illinois and is a common plant (see Distribution Map). Habitats include moist black soil prairies, rocky open woodlands, thickets, savannas, gravelly seeps, edges of marshes, remnant bogs, areas along ditches and railroads, and urban waste areas. This plant prefers disturbed areas, especially where fire has occurred. In prairies, it is found primarily near wetlands or moist areas with some woody vegetation.
Faunal Associations: Primarily wasps visit the flowers for nectar, including Paper wasps, Hornets, Eumenine wasps, and Spider wasps. Other insect visitors include long-tongued bees, short-tongued bees, and Tachinid flies. Mammalian herbivores leave this plant alone because of the bitterness and rank smell of the foliage.
Photographic Location: The photographs were taken along a railroad near Champaign, Illinois.
Comments: Another common name for this plant is Fireweed. The flowers of this plant are not very showy, and it is rather weedy in habit. The flowers are in bloom in the upper photograph, believe it or not. Pilewort has a distinctive appearance because of the flowers and can't be confused with any other species.