Showy Evening Primrose Seeds (Oenothera speciosa). In spite of its common name this naturalized specie can keep you guessing. In southern areas of Canada, flowers will open in the day while in more northern areas the flowers open very late in the day. Their fragrance is most noticeable in the evening. The flowers themselves start white then mature to pink, are about 5 cm (2") across and appear in profusion on upright 45 cm (18") stems. This primrose thrives in hot, dry soils in full sun and will readily reseed itself. Blooms tend to be largest in spring and then usually get smaller as the temperature goes up in summer. Showy Evening Primrose is suitable for use in sunny rock gardens and low borders in formal gardens.