Evening Primrose family (Onagraceae)
Description: This perennial plant is 2-5' tall, and is either unbranched or sparsely branched. The smooth stems are round or somewhat angular; they often become reddish in the sun near the inflorescence. The willow-like hairless leaves are up to 5" long and ¾" across. They are narrowly lanceolate or linear, with margins that are smooth or slightly serrated (widely spaced), and are sessile or with short petioles. The central stem and upper side stems each terminate in an elongated raceme of showy flowers, about 3-8" long. These flowers range in color from pink to magenta, depending on the local ecotype.
Each flower is about 1" across, consisting of 4 petals and 4 sepals. The petals are narrow at the base, but become broad and rounded toward their tips. The sepals are long and narrow; they are usually a darker color than the petals. In the center of the flower, there are up to 8 long white filaments with large magenta anthers; these anthers eventually shrivel and turn brown. The pedicels of the flowers are rather long and colored magenta. The blooming period occurs primarily from early to late summer, and lasts about a month. There is no floral scent. The flowers quickly wither away, and are replaced by seedpods that are long and narrow. These seedpods split into multiple sections, beginning at their tips (each section curling backward), and release a multitude of tiny seeds with small tufts of white hair. These seeds are readily dispersed by the wind, and can travel a considerable distance. The root system is fibrous and rhizomatous, which enables this plant to form colonies.
Cultivation: The preference is full or partial sun, moist conditions, and cool to warm temperatures. This plant becomes dormant during hot summer weather. The soil should contain abundant organic matter, with or without sand. A low pH is tolerated, if not preferred. This plant is fairly easy to grow, even under conditions that are not entirely suitable for it, but it has difficulty competing with plants that are better adapted to hot, dry summer weather. Foliar disease is not troublesome; however, the stems are easily broken. In warmer areas with a long growing season, Fireweed will bloom during early summer, while in cooler, boreal areas, it tends to bloom later in the summer.
Range & Habitat: The native Fireweed is a rare plant that occurs in only a few counties of NE and north central Illinois (see Distribution Map). It is more common further to the north in Wisconsin. Habitats include moist sedge meadows, woodland borders, damp ravines, sandy marshes near dunes, remnant bogs, and areas where trees and brush have been removed by fire. This plant is confined to cooler areas of Illinois where the climate has been made more moderate by the influence of the Great Lakes. It is not really a plant of the open prairies, but can be found sometimes in moist meadows. Fire stimulates the germination of this plant's seeds and helps to eliminate competitors, hence the common name.
Faunal Associations: Primarily long-tongued bees visit the flowers for pollen and nectar, including bumblebees and leafcutting bees (Megachile spp.). Smaller short-tongued bees and Syrphid flies also visit the flowers, but they seek pollen and are probably less effective at pollination (personal observations, Mitchell (1960/1962). Other insects feed on the foliage, sap, and other parts of Fireweed (Chamerion angustifolium), including such species as Altica tombacina (a flea beetle), Bromius obscurus (a leaf beetle), leaf-mining larvae of Mompha communis (a Momphid moth), larvae of Hyles lineata (White-lined Sphinx) and Hyles galii (Galium Sphinx), nymphs of Aphrophora gelida (Boreal Spittlebug), Aphis oenotherae (Evening Primrose Aphid), Aphis salicariae (Dogwood-Fireweed Aphid), and Aphis varians (Currant-Fireweed Aphid); see Clark et al. (2004), Needham et al. (1928), Wagner (2005), Marshall (2006), Robinson & Bradley (1965), and Blackman & Eastop (2013). Many of these insects are found north of Illinois where Fireweed is more common. The seeds of this plant are too small to be of much interest to birds. The foliage is palatable to various mammalian herbivores, but it has relatively low food value.
Photographic Location: The photographs were taken at the webmaster's wildflower garden in Urbana, Illinois.
Comments: Fireweed (Chamerion angustifolium) is attractive while in bloom, but it becomes ragged in appearance afterwards. This plant can't be confused with most willow-herb species (Epilobium spp.) because of their much smaller flowers. However, its flowers are similar in size to those of Hairy Fireweed (Epilobium hirsutum), which is not native to Illinois. This latter plant has spreading hairs that are soft and long, while Fireweed (Chamerion angustifolium) is hairless. A scientific synonym of this plant is Epilobium angustifolium.