Germination temperature
About 20-30 °C (68-86 °F).
Flower growing guide
Common evening primrose is a biennial whose fragrant yellow flowers open in the evening. Its tiny seed needs light to germinate, so it must be sown on the surface, not buried.
About 20-30 °C (68-86 °F).
Surface sow; do not cover.
About 15-20 days, usually within four weeks.
Needs light to germinate.
Optional: 3-4 weeks of stratification can improve germination.
Either; transplant while plants are young rosettes.
The seed is extremely small. Mix it with a little dry sand before sowing so it spreads evenly instead of falling in clumps.
Not needed.
Optional. Kansas State University recommends stratifying seed for three to four weeks to improve germination; other seed-starting guidance sows it without treatment. A practical method is to sow onto moist compost and keep the covered tray in a refrigerator for three to four weeks before moving it into warmth and light.
Not needed. Seed this small is hard to handle when wet; sow it dry onto moist compost.
The University of Alaska seed chart gives 20-30 °C (68-86 °F) for evening primrose. Laboratory work on Oenothera biennis found germination is induced best at about 32 °C (90 °F), with less light needed as temperature rises from 16 °C to 32 °C (61-90 °F). Warm conditions therefore suit it.
Sow on the surface and press the seed gently into the compost without covering it.
A fine, free-draining seed compost. In the garden it grows best on well-drained soil and tolerates low fertility.
Keep the surface constantly moist; uncovered seed dries out quickly. Water from below or mist, and cover the tray with clear plastic or glass, which lets light through.
Evening primrose seed is light-requiring: germination is controlled by phytochrome, the plant's light sensor, and seed that is buried or kept dark stays dormant. Buried seed can stay dormant in the soil for many years and sprout when the ground is dug and the seed is brought back to the light.
About 15-20 days in the Alaska chart; the USDA plant guide says seed usually germinates within four weeks.
Thin or prick out seedlings early and transplant them while they are still small rosettes; the plant forms a taproot. Space them at least 30 cm (12 in) apart, with 60-90 cm (2-3 ft) between rows.
In the first season the plant forms a flat rosette of leaves close to the ground. A few plants may flower in late summer of the first year.
In the second year it sends up tall, branched flowering stems and flowers from mid-summer into autumn, then dies after setting seed.
Cause: seed was covered with soil or sown too deep, so it had no light. Fix: resow on the surface and only press it in.
Cause: the dust-fine seed was sown unevenly. Fix: mix seed with sand before sowing and thin seedlings early.
Cause: root diseases in wet soil, or cold injury, between the first and second year. Fix: plant on well-drained soil or raised beds and sow a few extra plants.
Cause: this is normal. The flowers are partly closed by day, open in the evening and last one to two days. Fix: none needed; enjoy them at dusk.
Full sun gives the most flowers, though it tolerates partial shade. Evening primrose suits wildflower patches, borders and dry, sunny banks.
Because it is a biennial, sow every year for flowers every year. In India it grows most naturally in the hills, where it can be sown in spring or summer to flower the following year. In the plains, flowering after one season is less predictable; give plants a cool winter in the rosette stage and avoid waterlogged monsoon soil.
Evening primrose self-sows freely and has become invasive in many parts of the world. Cut the flower stems before the capsules split if you do not want seedlings everywhere.
Seed is ripe when the capsules begin to split. Cut the stems into a paper bag and shake out the seed.
Sow evening primrose for fragrant yellow flowers that open at dusk.
Yes. Germination is triggered by light, so sow on the surface of moist compost and do not cover the seed.
It is a biennial. Most plants form only a leafy rosette in the first season and flower in the second, though a few may bloom late in the first year.
It is optional. Three to four weeks of moist chilling can improve germination, but fresh seed sown on the surface in warmth and light also germinates.