|O.elata subspecies hookeri, is an upright perennial or biennial, blooming in masses of pale yellow primroses that turn to orange-red, opening at dusk. Leaves are lance-shaped in a mid-green. 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.