|O.speciosa, a perennial with rosettes close to the ground, mid-green, lance-shaped leaves 1-2 inches long. The delicately fragrant white primroses, sometimes turning to pink, open in the daylight hours, blooming from June to August. Best planted in spring among other full sun plants. You should divide the clumps every 3 years to encourage them to flower. Evening Primroses are excellent perennials for weekend gardeners, since they are simple to grow, with almost no pests or problems.