Oenothera triloba
stemless evening primrose
Overview
Oenothera triloba is a stemless biennial or short-lived perennial of the evening-primrose family, native to the central United States. It forms a flat basal rosette of deeply lobed, dandelion-like leaves 2-6 inches (5-15 cm) high and 8-16 inches (20-40 cm) across, pressed close to the ground. Lacking an upright stem, the pale yellow four-petaled flowers open directly in the center of the rosette. Each bloom is 1-2 inches (2.5-5 cm) wide on a long floral tube, opening in late afternoon and evening with a light fragrance that draws night-flying moths, then fading by the next midday. Flowering runs through spring. The flowers give way to hard, four-winged woody capsules that sit in the rosette and persist after the leaves die. O. triloba grows on dry prairies, limestone glades, and rocky or gravelly open ground, and needs sharp drainage and full sun. It is short-lived and depends on self-sown seed to renew, and it fades quickly in rich, moist, or shaded soil.
Native Range
Native to the central United States, from Nebraska and Kansas south through Oklahoma and Texas, with scattered populations eastward and into northern Mexico. It grows on dry prairies, rocky glades, pastures, and disturbed open ground.Suggested Uses
Grown in rock gardens, dry native plantings, and prairie restorations on lean, gravelly soil. The evening flowers support night-flying moths. The persistent winged capsules are used in dried arrangements.How to Identify
Appearance
Size & Dimensions
Height2" - 6"
Width/Spread8" - 1'4"
Bloom Information
Flowers open through spring, mainly April to June. Each pale yellow bloom opens in late afternoon or evening, releases a light scent, and closes by the following midday. Night-flying moths are the main pollinators.
Detailed Descriptions
Foliage Description
greenGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Plants need full sun and dry, sharply drained rocky or sandy soil. Water is needed only to start young rosettes, after which the plant tolerates heat and drought. Hardiness runs from about USDA zone 4 to zone 8, and the rosette overwinters through frost. Rich, moist, or shaded soil rots the crown and shortens the plant's already brief life. No fertilizer is needed on lean ground. Because it is short-lived, leaving some capsules to shed seed keeps a stand going.Pruning
No pruning is required. Old flower capsules and dead leaves can be cleared once the rosette declines. Leaving a few capsules to ripen maintains self-sown replacements.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summer
Container Growing
✓ Suitable for container growing
Minimum container size: 2 gallons