Evening Primrose

There are several species of evening primroses, (Oenothera), that are native to North America and they are often listed in wildflower books.  But in Michigan the evening primrose tribe is most likely to be found in gardens  and so it will be listed here as a garden plant.  Most gardeners can grow the evening primroses; they are hardy to at least zone 4.  Domesticated evening primroses bloom over a long period and are very easy to grow.  They are often used as filler in perennial beds.

The name evening primrose is confusing, as common names can be, because Oenothera are not related to the true primrose family and many species stay open in the daytime as well.  Oenothera missouriensis is commonly called Sundrops or Missouri primrose.  It is a compact plant with 5 inch yellow flowers that stay open during the day.  The other evening primrose commonly found in Michigan gardens is the Showy evening primrose or Oenothera speciosa, which gets about 30 inches tall with pretty light pink flowers.

Two other varieties of evening primrose may turn up in gardens. The common evening primrose, Oenothera biennis, which is a rangy plant that can get up to 5 feet high in good conditions, has small yellow flowers that do open in the evening. The prairie evening primrose, Oenothera albicaulis, has white flowers.

The cutleaf evening primrose, ( Oenothera laciniata), is a weed of nursery pots and sometimes in fields.  It forms a rosette of lobed, deeply cut leaves with a prominent white vein.  It blooms close to the ground with yellow or reddish small flowers and is not a suitable garden subject.

Description of garden varieties

The leaves of most evening primrose are narrow ovals with a toothed edge.  Stems are reddish, with small hairs. Plants may branch near the top. Plants grow higher through the summer, putting out new clusters of flowers.

Evening primrose flowers open in clusters at the top of the plant.  Each flower has 4 petals and a slightly glossy look.  The showy evening primrose has darker pink veins on the light pink flowers. Flowers are lightly fragrant. The flower size ranges from 1-5 inches wide.

Care of evening primroses

Primroses thrive in dry sunny, places but will also grow in partial shade. They will grow even in poor soil, but it must be well drained.  Gardeners will generally buy plants but evening primroses can be started from seed. Seed actually germinates quite well outside, sow it in midsummer and it will bloom the second year. They are bi-annual or short lived perennials but will spread generously for you by seed.  Many gardeners get their evening primrose plants from other gardeners who need to thin them out after a few years.

Evening primroses are easy garden plants; they don’t require fertilization in all but the poorest soils and have few pests and diseases.  Taken alone they don’t make much of a statement in the border; they should be planted in generous groups.  Showy evening primrose in particular makes quite a show when planted in large drifts. If they are in a spot they like evening primroses will bloom for much of the summer. 

Occasionally the prolific evening primroses will be found where they have escaped the garden, usually in dry, sunny meadows.  In Michigan wild primroses are generally the yellow common evening primrose.  They are sometimes included in wildflower seed mixes.

Herbal use

Native American women chewed the seeds of common evening primrose for menstrual pain, PMS symptoms and other “woman” problems, including breast pain. The seeds are sometimes ground for herbal remedies.  In recent years the extracted oil of evening primrose seeds is being studied for a whole slew of reasons, pain relief and heart health are a few, and it is used in cosmetics for its supposed anti-aging properties.

Be careful using evening primrose oil as it can cause stomach upset and diarrhea and some people have serious allergic reactions to it.