It’s fitting that the ‘speciosa’ in the botanical name of this plant (Oenothera speciosa) translates to “showy.” The lovely white to pale pink blossoms feature four overlapping petals and grow between 1 1/2 and 3 inches in size. They catch the attention of gardeners everywhere but must be planted selectively, as they have a tendency to multiply and overtake cultivated land. Pink evening primrose has a moderate growth rate and is usually planted in late summer or early fall. Pink evening primrose will reproduce through self-seeding and runners (called stolons), so this is something to be aware of. Pink evening primrose is generally recommended for landscapes where you need a soft, abundant ground cover. They also make a great addition to a wildflower patch. However, they can be very challenging to use in manicured gardens and will require vigilance against spreading.
Light
Pink evening primrose is adaptable to different amounts of light, depending on your objectives for this plant. If you’re looking for a showy, flowering plant, then you’ll need to plant this perennial in full sun. If you want a dense, quickly growing ground cover, then pink evening primrose does just fine in full shade, though it will not flower. Instead, you’ll have branching green leaves that are about 1 to 3 inches long.
Soil
Plant pink evening primrose in loose, well-draining soil for best results. It does fine in rocky, sandy, or clay soil types. While many other flowering plant species thrive in rich soil, pink evening primrose actually prefers poor soil. This makes it a good option if you have an inhospitable spot in your garden or yard that you’d like to cultivate.
Water
A moderate consumer of water, pink evening primrose blooms best when it receives a steady supply of water. In the first year, it’s recommended that you water this plant weekly to help it thrive, but moving forward, available rainfall is generally sufficient. Because it is a drought-tolerant species, you won’t need to worry much if rainfall is spotty or inconsistent. However, keep in mind that a water shortage may cause this plant to go dormant and cease bloom production. If you want to keep it active all summer long, then supplement any rainfall shortage with weekly or bi-weekly watering. To avoid overwatering, let the soil dry in between watering sessions. Too much water can lead to a variety of problems, including root decay, fungal problems for foliage, and discolored leaves.
Temperature and Humidity
Pink evening primrose has proven itself adaptable to various climates by naturalizing in 28 of the lower 48 states. This plant is reliably hardy in USDA zones 5 to 8 but may survive in zones 4 and 9, as well. They tend to grow best in temperate to warm climates. They can withstand heat better than cold temperatures.
Fertilizer
Given that pink evening primrose does best in poor soil, it’s generally not advantageous to fertilize this plant species. The extra nutrients are of little value to this flower that seems to enjoy neglect more than nurturing.
Types of Evening Primrose
Pink evening primrose, has several popular named cultivars:
‘Alba’ is a white-flowered variety.‘Golden Summer’ has very attractive golden foliage.‘Twilight’ has pink flowers with unusual purple variegated leaves.
In addition, the Oenothera genus has many similar species with different flower colors, often identified by their native region or preferred habitat. Among those that are sometimes cultivated as garden plants:
Mexican evening primrose (O. berlandieri): This species is native to the Southwest and West Coast. Very similar to O. speciosa, it is somewhat less aggressive than that plant. Two excellent cultivars are ‘Siskiyou’, with 2-inch pink blossoms, and ‘Woodside White’, a white cultivar, It is hardy in zones 6 to 8.Narrowleaf evening primrose (O. fruticosa): Also called sundrops, this species is native to eastern North America and produces bright yellow flowers in late spring. It is hardy in zones 3 to 9 and has several named cultivars, including ‘Lady Brookeborough’.Ozark sundrops (O. macrocarpa): This species has very large yellow flowers, up to 5 inches across. Two worthy cultivars include ‘Greencourt Lemon’ and ‘Lemon Drop. This species is hardy in zones 4 to 7. Common evening primrose (O. biennis): This biennial is native to the central and eastern U.S. and produced lemon yellow flowers in its second year. It is hardy in zones 4 to 9.
Pruning
No pruning is required for the health of the plant, but shearing them back after flowering may reduce the self-seeding that causes the plant to spread so aggressively. Pinching back the spent flowers may also prompt a longer bloom period.
Propagating Pink Evening Primrose
If you wish to multiply pink evening primrose plants, you’ll have no difficulties—they are easily propagated through root division, by rooting cuttings, or by collecting and sowing seeds. The easiest way is by simply digging up and transplanting the offshoot plants that are produced when underground stolons take root and sprout above ground. Here’s how to do it:
How to Grow Evening Primrose From Seed
This plant will readily sprout if you collect seeds from the spent flowers and direct sow them in loosened soil. Fall is the best time to scatter seeds. It is also quite easy to identify self-seed volunteers that sprout up around the parent plant in spring and transplant them into new locations.
Overwintering
When grown within its recognized hardiness range, pink evening primrose does not require any protection against winter cold. But you should withhold water and let the plants go somewhat dry during the late fall and winter, as they dislike sitting in damp soil during cool weather. You may want to cut back and destroy the old flower heads and stems to prevent volunteer seedlings from sprouting up in the spring.
Common Pests and Plant Diseases
Pink evening primrose has no notable pest enemies, but it can be prone to root rot fungus if planted in soil that is consistently wet or if it is overwatered. Plants that develop root rot should be removed. Fungal leaf spots or powdery mildew can also be occasional problems in humid conditions but are rarely serious.
How to Get Pink Evening Primrose to Bloom
All that’s required for pink evening primrose to enjoy its typical long bloom period from summer into fall is for them to get plenty of direct sunlight. A full six hours or more of direct sunlight will create the best flower display. Individual blossoms are short-lived, but the plant continues to rebloom for months. Extended drought can reduce flowering, so keep the plants adequately watered during dry periods.
Common Problems With Pink Evening Primrose
The most often cited complaint with this plant is from gardeners who start out with great admiration for this plant, then become disillusioned as the reality sets in: Pink evening primrose planted in rich, well-draining soil can become a weedy marauder against which you are constantly battling to prevent it from conquering nearby territory. All too often, gardeners eventually resort to carefully applied broad-spectrum herbicides to beat back the plant’s invasion. Pink evening primrose is best reserved for large areas of poor, rocky soil where it can naturalize to become the attractive but weedy ground cover it wants to be.
The seeds of the evening primrose plant are frequently harvested as a natural source of Omega-6 fatty acids—but birds love them too, so you’ll have competition for gathering them.
