Ragged Evening Primrose
Oenothera laciniata
Evening Primrose family (Onagraceae)

Description: This plant is an annual about –2' long that often sprawls across the ground, or it is weakly ascending (particularly near the tips of its branches). Small plants are usually unbranched, while larger plants produce lateral stems occasionally. Each stem is terete, light green, and more or less hairy. Along each stem, there are alternate leaves up to 4" long and 1" across. The leaves are oblong-lanceolate to oblong-oblanceolate and pinnatifid; they are hairy, although less so along their upper surfaces. The middle to upper leaves are sessile, while the lower leaves have short petioles. From the axils of the middle to upper leaves, there develops individual flowers that are sessile. Each flower spans about 1" across when it is fully open, consisting of 4 yellow petals, a narrowly cylindrical calyx (about 2" long) with 4 narrowly triangular lobe-segments at its apex, a narrowly cylindrical ovary/fruit (about 1–1" long), 8 stamens, and a central united style with cross-shaped stigmata. The flowers bloom at night and become closed during the morning. Even though it appears that each flower has a stalk-like pedicel about 3" long, this is actually the narrowly cylindrical calyx and ovary/fruit of the flower. The lobe-segments of the calyx hang downward. The blooming period occurs from late spring to mid-summer and lasts about 1–2 months. Only a few flowers are in bloom at the same time. After pollination of a flower, the entire calyx becomes pale salmon pink and falls off the fruit. The cylindrical fruit (or developing seed capsule) is straight to slightly curved and ascends upward; it is terete, slightly 4-ribbed, and more or less pubescent along its length. This plant reproduces by reseeding itself; the surfaces of the small seeds are pitted.

Cultivation: The preference is full sunlight, mesic to dry conditions, and sandy soil where the ground vegetation is low and sparse. Most growth and development occurs during the cool weather of spring.

Range & Habitat: Ragged Evening Primrose is occasional throughout Illinois (see Distribution Map), where it is native. Habitats include sand prairies, hill prairies, sandy fields and meadows, areas along railroads, roadsides, and waste areas. Usually this wildflower is found in disturbed sandy habitats, although it is occasionally found in barren gravelly areas. It is somewhat weedy.

Faunal Associations: The flowers are pollinated by Sphinx moths and, to a lesser extent, by bumblebees, honeybees, and other long-tongued bees. Small bees and Syrphid flies may also visit the flowers, where they collect or feed on the pollen, but these latter insects are less effective at cross-pollination. Insects that feed on Ragged Evening Primrose and other Oenothera spp. include several aphids, flea beetles, weevils, moths, and other insects (see the Insect Table for a listing of these species). The Mourning Dove has been observed eating the seeds, while the Cottontail Rabbit and White-Tailed Deer often browse on the foliage.

Photographic Location: A sandy meadow at the Heron Boardwalk in Vermilion County, Illinois. Because the photograph was taken during the early morning, the flower and foliage were still covered with dew; the flower is already beginning to close.

Comments: Because the flowers usually bloom at night, Ragged Evening Primrose is a fairly low and inconspicuous plant. These flowers are very similar in appearance to those of Oenothera biennis (Common Evening Primrose) and other species in this genus. It is primarily the pinnatifid shape of the leaves that sets Ragged Evening Primrose apart; they have conspicuous lateral lobes. The leaf-margins of other Oenothera spp. in Illinois are usually less wavy. Another common name of Oenothera laciniata is Cutleaf Evening Primrose.