Oenothera biennis, Evening Primrose, is wildflower native to Michigan and the UP. It is a biennial, but readily reseeds in exposed soil. It can reach 6 feet tall in ideal conditions, but a more typical Upper Peninsula height is 3 feet. Currently and historically used for medicinal purposes and as a food source.
It prefers medium to dry loamy sites, but can tolerate poor gravelly or sandy soils, making it well suited to many difficult areas. Once established, avoid overwatering. In a dense planting or unamended soils, it stands nicely upright with a long stalk, or multiple stalks, of yellow flowers in the second year. Rich soil, shade, or too much space can make it sprawl. Primrose is particularly well suited to naturalizing into meadows. Prefers full to part sun.
The blooms are fragrant and go from early summer until frost, sometimes persisting after the first light frosts! The dry stalks with four-chambered seed compartments spiralling upwards add winter interest to your landscape.
The host-plant value of Evening Primrose cannot be overstated. It is the only host plant for the beautiful pink and yellow Primrose Moth - with a relationship as tightly knit as that of Monarchs and Milkweed. Primrose moths time their adult emergance to conincide with the development of Primrose seed pods, which is their larval food. They lay an egg on a pod and the pink and green caterpillar eats the pod. This will not harm the plant; Primrose will still make plenty of seeds. The pretty adult moths nectar on the flowers, pollinating them, and you may find them sleeping on the plant in the day. It is also a host for the White-lined Sphinx/Hummingbird Moth.
As its name suggests, Evening Primrose flowers open suddenly in the evening, making them of particular use to moths and other nighttime pollinators, but they are open in the day long enough to be of use to butterflies and many kinds of bees. The seeds are important for birds, and flowers are visited by hummingbirds.
The seeds require light to germinate. If you want this plant to reseed vigorously, pull back mulch and control weeds to expose soil until the first-year rosettes are established. This plant seeds prolifically and will spread in areas with exposed soil. Pull the first-year rosettes to control, if necessary. May not be well suited for small or formal plantings, but worth its weight in gold as a habitat plant if you have the space.