Prairie Sundrops (Oenothera pilosella)
- Family: Evening Primrose (Onagraceae)
- Flowering: May-July.
- Field Marks: This species has a 4-sided ovary, a 4-sided capsule, large yellow flowers, and spreading hairs on the sepals.
- Habitat: Fallow fields, wet prairies, roadside ditches.
- Habit: Perennial herb with fibrous roots.
- Stems: Erect, sometimes branched, with spreading hairs, up to 2 feet tall.
- Leaves: Alternate, simple, lanceolate to elliptic, pointed at the tip, tapering to the base, with minute teeth or toothless, hairy, up to 4 inches long, up to 1 1/2 inches broad.
- Flowers: Several in terminal clusters, bright yellow, showy, up to 2 1/2 inches across.
- Sepals: 4, green, hairy, up to 3/4 inch long, united below to form a long tube.
- Petals: 4, yellow, free from each other, up to 1 1/4 inches long.
- Stamens: 8.
- Pistils: Ovary inferior; stigmas 4.
- Fruits: Capsules 4-angled, usually hairy, up to 2/3 inch long.
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