Oenothera macrocarpa Nutt.

Missouri Evening Primrose


CC = 7
CW = 5
MOC = 40

© SRTurner

Family - Onagraceae

Habit - Perennial forb with a stout, woody, often somewhat branched, vertical rootstock, sometimes producing new shoots from lateral roots.

Stems - Spreading to loosely ascending, one to several, to 60 cm, unbranched or with few to several branches, glabrous to densely pubescent with short, appressed, nonglandular hairs, strongly reddish-to dark purplish-tinged.

Oenothera_macrocarpa_stem.jpg Stem and ovaries of flowers.

© SRTurner

Leaves - Alternate, simple, 4-12 cm long, 4-25 mm wide, lanceolate to broadly elliptic, short-to moderately petiolate, the margins entire to somewhat irregular or wavy or with short, broad, broadly spaced teeth, hairy, the surfaces pubescent with appressed, nonglandular hairs, densely so on young leaves, often less densely so at maturity (but often grayish-tinged, as well as with reddish splotches), the secondary veins usually relatively inconspicuous.

Oenothera_macrocarpa_leaf1.jpg Leaf adaxial.

© SRTurner

Oenothera_macrocarpa_leaf2.jpg Leaf abaxial.

© SRTurner

Oenothera_macrocarpa_pressed_leaves.jpg Pressed leaves.

© DETenaglia

Inflorescences - Axillary flowers, the bracts not differentiated from foliage leaves.

Flowers - Actinomorphic, opening at dusk and usually remaining open into the following morning, the floral tube 95-115 mm long, pubescent with short, appressed, nonglandular hairs and minute, glandular hairs. Sepals 50-65 mm long, glabrous or with dense, appressed, nonglandular hairs, the free tips in bud 8-10 mm long, erect and appressed. Petals 55-65 mm long, 48-64 mm wide, broadly obovate, yellow to bright yellow, not fading or fading to orange. Stamens with the filaments 30-40 mm long, ascending to somewhat S-shaped or curved toward the top of the flower, glabrous at the base, the anthers 17-24 mm long, yellow. Style 55-190 mm long, the stigma deeply 4-lobed, the lobes 7-13 mm long.

Oenothera_macrocarpa_bud.jpg Flower bud opening.

© DETenaglia

Oenothera_macrocarpa_flowers.jpg Flowers.

© SRTurner

Oenothera_macrocarpa_calyx.jpg Calyx.

© SRTurner

Oenothera_macrocarpa_corolla.jpg Corolla.

© SRTurner

Oenothera_macrocarpa_functional.jpg Stamens and anthers (left) and style and stigma (right).

© SRTurner

Fruits - Capsules 52-75 mm long, overall broadly oblong-elliptic to oblong in outline, the main body longitudinally dehiscent, 4-locular, 50-70 mm long, 6-8 mm in diameter, narrowly ellipsoid, not flattened, strongly 4-winged, each wing 18-28 mm wide, flat to somewhat undulate, rounded or truncate at the tip, becoming tan and papery at maturity, tapered abruptly to a sterile, stalklike base 2-6 mm long. Seeds numerous in each locule, arranged in a single row, 3-5 mm long, mostly 1.8-2.3 mm wide, obovoid, the surface grayish brown to dark brown, coarsely wrinkled and usually somewhat corky. Self-incompatible.

Oenothera_macrocarpa_fruit.jpg Fruit.

© SRTurner

Flowering - May - August.

Habitat - Glades, bluffs, rocky prairies, quarries, roadsides, on calcareous substrates.

Origin - Native to U.S.

Lookalikes - None.

Other info. - This is one of the most characteristic of Missouri Ozark species. The giant yellow flowers, red-speckled foliage, and curious winged fruits make it impossible to mistake for anything else. It is found in the southern half of Missouri, except for the region of the Bootheel, where it is apparently absent. It is not a particularly widespread species, with a U.S. distribution largely confined to four states (Missouri, Kansas, Oklahoma, and Texas).

This is a fantastic garden species, with all parts of the plant having an interesting appearance. It grows well from seed and is drought tolerant. It is available through nurseries specializing in native plants and is richly deserving of widespread cultivation. The flowers open at dusk and last only one night. If the next morning is cloudy the flowers will remain open. With age, the large winged fruits detach from the stems and tumble across the landscape, dispersing the seeds.

Missouri plants are referable to ssp. macrocarpa. Three other subspecies are recognized from the same general region of the country, each occupying a slightly different geographical area and habitat type. They are relatively well differentiated by pubescence, leaf features, flower and floral tube size, and size and morphology of the fruits and seeds.

Photographs taken in Eminence, MO.,5-28-03 (DETenaglia); also at Shaw Nature Reserve, Franklin County, MO, 5-19-2006 and 7-1-2006, and at Valley View Glade Natural Area, Jefferson County, MO, 5-18-2010 and 5-24-2014 (SRTurner).