Evening primroses have large cup-shaped flowers that are often fragrant. There's a variety to choose from-different types bloom in shades of yellow, white, or pink. Many plants have flowers that open in the evening rather than the day-thus their common name.
- Common name: Evening primrose
- Botanical name: Oenothera spp.
- Zones: 3 to 9, depending on species
- Size: To 5 feet tall, depending on species
- From: Areas of North and South America
- Family: Onagraceae (fuchsia family)
- Sun: Full sun to partial shade
- Soil: Moist, well-drained soil and full sun. Good drainage is important for the plants-heavy clay soils should be amended before planting.
- Moisture: Some species are drought resistant; others need moisture in times of drought.
- Mulch: It's advantageous to lay a 2- to 3-inch-deep layer of mulch over the soil around the plants. Use winter mulch only after the soil has frozen.
- Pruning: Cut plants back in autumn after freezing temperatures arrive or in spring before plants begin to grow.
- Fertilizer: Fertilizer is generally not necessary in soils that are rich in organic matter. If desired, use a balanced fertilizer in spring.
- Seed: Plant evening primrose seeds in early spring in a cold frame or sheltered spot in the garden.
- Aphids: If plants are attacked by large numbers of very small insects at the tips of the new growth, it's probably aphids. Try repeatedly spraying aphids off plants with a stream of water from the garden hose, encouraging beneficial insects, or applying insecticidal soap or horticultural oil.
- Fungal diseases: Deter them by pruning the plants to encourage good airflow, avoiding wetting the foliage, and mulching the soil around the plants.
- Gray mold: Gray mold starts out as a leaf spot and may develop into fuzzy gray areas on the plant.
- Leaf spot: In summer or autumn, the leaves develop yellow or brown spots with concentric rings around them, forming something of a bull's-eye pattern.
- Powdery mildew: This disease tends to appear in mid- to late summer. The mildew looks like a gray powder covering affected leaves. The leaves gradually drop off.
- Rust: It usually looks like leaf spotting that's followed by small masses of rusty-colored powder forming on the leaves. Infected leaves die by the end of the season.
- Garden Note
- Some species, such as O. macrocarpa, can easily spread through the garden faster than a gardener would like. Take care when planting these vigorous species.
- Oenothera acaulis: Grows to around a foot tall with trumpet-shaped white summertime flowers that open in the evening. Zones 5 to 9.
- Oenothera fruticosa: Grows to around 3 feet tall with brightly colored yellow summertime flowers that open in the morning. Zones 4 to 8. Native to areas of North America.
- Oenothera fruticosa ‘Fireworks': Grows to around 2 feet tall with red stems and brightly colored yellow summertime flowers that open in the morning. Zones 4 to 8.
- Oenothera macrocarpa: Grows to about one foot tall with brightly colored yellow flowers in summer and autumn. Zones 5 to 8. Native to areas of North America.
- Oenothera pallida: Grows to 2 feet tall with white flowers that open at dusk in summer and autumn. Zones 3 to 7. Native to areas of North America.
- Oenothera speciosa: Grows to 1 foot tall with summertime pinkish-white flowers that open in the morning. Zones 5 to 8. Native to areas of North America.
Photo courtesy of Proven Winners