Evening Primrose family (Onagraceae)
Description: This herbaceous perennial plant is 1-4' tall, branching occasionally. The stems are square or round, and usually pubescent where new growth occurs, becoming glabrous with age. The hairless leaves are opposite or alternate along the stems, sessile or with short petioles, and up to 4" long and ½" across. They are narrowly lanceolate in shape, and sometimes have purple veins or spots. There are 4-8 teeth per centimeter along the margin of each leaf.
From the upper axils of some of the upper leaves, there appears a single flower with a long calyx tube on a short stalk (peduncle). This calyx tube is pubescent and more or less erect, terminating in 4 lanceolate sepals that often tinted purple or pink. These sepals are a little shorter than the petals. The 4 notched petals are white or light pink, and span about 1/3" across. At the throat of the flower, there is a prominent pistil that is often knobby at the end, which is surrounded by several stamens. These flowers bloom for about a month during late summer or early fall. The calyx tube matures into an elongated seed capsule, which splits open to release a multitude of tiny seeds with small tufts of reddish brown hair. These seeds are distributed by the wind. The root system is fibrous and produces rhizomes, which enables this plant to spread vegetatively.
Cultivation: The preference is full sun to light shade, and wet to moist conditions. The soil should contain lots of organic material to retain moisture. The foliage is rather fragile and can become damaged easily. This plant tolerates occasional flooding, and prefers rather cool conditions.
Range & Habitat: The native Cinnamon Willow-Herb occurs occasionally in northern and central Illinois, but it is uncommon or absent in the southern section of the state. Its range extends further to the south than other Epilobium spp., which are usually restricted to northern Illinois. Habitats include poorly drained areas of black soil prairies, moist woodlands, woodland borders, and various kinds of wetlands, including marshes, bogs, fens, seeps, and edges of ponds, rivers, or drainage ditches. The Willow Herbs are pioneer species that thrive on some kind of disturbance, such as fire.
Faunal Associations: The flowers probably attract bees and flower flies, which seek nectar and pollen. The caterpillars of various moths eat the foliage of Willow-Herbs, including Hyles lineata (White-Lined Sphinx), Eudryas unio (Pearly Wood Nymph), Anticlea multiferata (Many-Lined Carpet), and Scythris magnabella (Scythridid Moth sp.). The seeds are too small to be of much interest to birds. The foliage is non-toxic and occasionally eaten by mammalian herbivores, but it has low food value.
Photographic Location: A poorly drained area of prairie in Meadowbrook Park, Urbana, Illinois.
Comments: The flowers are rather small-sized, but they are often produced in abundance on large plants. The most distinctive characteristic of Cinnamon Willow-Herb is the reddish brown coloration of the tufts of hair on the seeds, which is responsible for the common name of this plant. Other Epilobium spp. have tufts of hair that are white or faded brown or grey. Cinnamon Willow-Herb also has serrated leaves with 4-8 teeth per centimeter, while other Willow-Herbs have leaves with either smooth edges or fewer teeth per centimeter. An unusual characteristic of the Willow-Herbs is the long calyx-tube of the flowers, which occurs behind the petals, and eventually becomes an elongated seed capsule. It looks like a flowering stalk (peduncle), but it is actually part of the flower where the ovaries are contained. In some members of the Mustard family and miscellaneous other plants, an elongated seed capsule develops in front of the petals. This is one way to determine whether the plant in front of you is a Willow-Herb, or a quite different species of plant.