Prairie Sundrops
Oenothera pilosella
Evening Primrose family (Onagraceae)

Description: This herbaceous perennial plant is up to 2' tall and sometimes bushy. The stems are covered with conspicuous white hairs. The sessile alternate leaves are up to 3" long and 1" wide, lanceolate or ovate, with smooth to slightly dentate margins. They are pubescent on both the upper and lower surfaces. The inflorescence at the top of the plant consists of a short cluster of flowers or hairy buds. These flowers are bright yellow and individually about 2" across. Each one has four large petals, large showy stamens, and fine white or transparent lines that radiate outward from the center of the flower. These lines function as nectar guides, and are more visible to insects than humans in the ultraviolet spectrum. The blooming period occurs during late spring or early summer and lasts about a month. The flowers bloom during the day and have a pleasant fragrance. The seeds are without tufts of hairs, while the root system is highly rhizomatous. In disturbed areas, colonies of plants are readily formed. The new growth during early spring and older foliage during the fall often acquire reddish tints.

Cultivation: The preference is full sun, moist conditions, and a loamy soil with high organic content. This plant develops quickly during the spring and flowers readily. Later in the year, it becomes dormant and less attractive in appearance, but can tolerate some drought. This plant is easy to grow if it is not too dry, and can spread aggressively.

Range & Habitat: The native Prairie Sundrops occurs occasionally in the majority of counties in Illinois; it is uncommon or absent in central and NW Illinois (see Distribution Map). Habitats include moist to mesic black soil prairies, edges of pothole marshes, abandoned pastures, and prairie remnants along railroads.

Faunal Associations: The flowers are pollinated primarily by long-tongued bees, butterflies, and skippers. Halictid bees and Syrphid flies often visit the flowers, but they are attracted by the abundant pollen and cannot be considered very effective at pollination. Among the long-tongued bees, are such visitors as Little Carpenter bees and large Leaf-Cutting bees, which suck nectar or collect pollen. The foliage is eaten occasionally by rabbits, and probably other mammalian herbivores.

Photographic Location: The photographs were taken at the webmaster's wildflower garden in Urbana, Illinois.

Comments: This lovely plant should be grown more often. During the 19th century, this was a more popular garden plant, but it has since passed from favor and is not widely available. Prairie Sundrops resembles Oenothera fruticosa, but differs from the latter by its hairy leaves. The latter species has a range that lies east and south of Illinois, and is widely available through horticultural sources.