Mexican evening primrose (Oenothera speciosa), also known as pink evening primrose, is an 8- to 24-inch tall perennial flower that is cold hardy in USDA zones 5 to 9. Late spring to late summer, Mexican evening primrose will produce fragrant pink blooms with yellow centers. You can plant Mexican evening primrose seeds outdoors in the spring, or anytime summer to fall. Plant container Mexican evening primrose in the spring.
Choose a full-sun, well-drained location to plant Mexican evening primrose. The plant will spread, so choose a location where spreading is welcome, like on a hillside. This perennial will grow in most soil conditions, sandy to some clay, and will even grow in rock gardens.
Break up the surface of the ground down to 2 to 3 inches using a hoe or three-prong rake if planting seed. The soil can be worked deeper if desired. Water the worked soil lightly so seeds will adhere. If planting container Mexican evening primrose, use a spade to dig a hole down and across twice the height and width of the container to loosen the soil. Space container plants 24 inches apart.
Spread the seeds on the moist soil. When the sprouts appear in less than two weeks, gently pull out weaker sprouts. When planting from a container, remove the plant from the container. Back fill the hole as needed so top of the plant is at ground level.
Water newly planted Mexican evening primrose every seven to 10 days during the first growing season if there is no rainfall. From the second year on, rainfall alone should provide this drought-tolerant plant with sufficient water.
Dig up the plant every three years and divide the root ball into two sections (divisions). The division can be planted elsewhere to expand the Mexican evening primrose flower bed.