Oenothera, Evening Primrose

Ilona Erwin

Oenothera, Prairie Beauty

Evening primrose is the name for a number of pretty flowering plants in the Oenothera genus, belonging to the Onagraceae family of plants. Related in this family are the Gauras, Fuchsias, and Clarkias -as well as the different Oenotheras.

As you might guess from the name, Evening Primrose flowers are open in the evening and mornings, sometimes midday when the skies are cloudy.

Oenothera that flower in the day are known as Sundrops, while those that open late in the day and close the next morning are called Evening Primroses.

Garden Worthy Primroses

O. speciosa

Oenothera speciosa, the pink evening primrose
Also known as the Mexican primrose, this is a perennial flower which is native to a large part of the United States. The beautiful dawn pink flowers have a sunny yellow center and are low to medium growing plants, to between 8- 24 inches. Native to prairies and savannas of the lower Midwest states, they like well drained soils and sunny exposures. Hardy Zones 5 – 9. There are named varieties of this popular garden plant.
Oenothera fruticosa, Sundrops
This produces a sunny bright yellow spot in the garden. Hardy to Zone 4. Long bloom that starts in late June/early July.
Oenothera biennis, the common evening primrose
When found in their native tall grass prairie environment this reach native biennial plant can be 8′ tall. It is more like four feet in your garden. Attractive yellow flowers grow with willow like foliage that is a soft olive green color. A biennial flower, like the name indicates.

Others worth looking into:

  • Oenothera acaulis, with white flowers Zone 5 hardy
  • Oenothera pallida, pale flowers, hardy to Zone 3, 2′ tall
  • Oenothera macrocarpa, 1′ tall, similar to O.fruticasa
Many Evening Primroses have a lovely fragrance

The look

evening primrose

evening primrose closup

Large four petaled flowers in wide bowl shape, the stamens have a distinctive cross shape. They can be a shade of yellow or sometimes pink, their green stems and leaves are often tinged red along the edges.

How to grow

Either buy plants or seeds, to plant in the spring.

photo by N. Houlihan

Golden Sundrops

Evening primroses are easy to grow from seeds which are sown in situsown directly into the ground. Perennial types of Oenothera can be divided in spring for new plants. They generally like full sun. There are annual and perennial types, and a wide range of heights. Usually yellow, the pink O. speciosa is a most beautiful sweet pink color. The leaves are lanceolate and relatively inconsequential to the flowers.

They like disturbed ground, and not too much competition from other plants. Rabbits and groundhogs like to eat them, and that was the likely demise of my own stand of pink primroses.

I grew some O.biennis long ago and remember how long it took to germinate. What I know now is that the seeds could use some help through stratification and light to break their dormancy.

Some types, like O. speciosa, may be invasive

Use and Companions

Oenothera biennis

evening primroses

These are plants for meadows, prairies and wild gardens, although the more compact types such as O. fruticosa and O. speciosa look good in borders, mid to front locations. They make a good solid drift of colorful flowers. The biennial Evening primrose is more rangy and looks best mixed into more substantial foliage. Try it among stands of iris, which be done blooming.

Pretty with the harmonizing colors and contrasting bloom forms of daylilies and heleniums, all of which bloom midseason.

Sunny flower beds, xeriscape gardens, and on slopes are good places to plant Oenotheras. Native to the USA, this makes them ideal for those who wish to grow plant natives in their landscape.

  • Known as a a primary colonizer, able to rapidly exploit patches of bare ground, but doesn’t compete well in an established plantings.(more about plant succession)
  • The evening primrose plant Oenothera biennis is a biennialits life cycle takes two years. Use them similarly to foxgloves and sweet williams (all of which are biennials).
  • O.specisoa and Oenothera fruticosa are perennials

Fun Facts

The family name ‘Onagraceae‘ means food of the “onager” or as we know them -wild Asian donkeys.Oenothera means “wine-scented or scenting”.

“The modern name Oenothera was given by Linnaeus and said to be derived from the Greek “Oenothera” for “wine-scenting” (Bailey, 1953; and Bailey, 1958) ”

Evening Primroses can be eaten in salads or as a root vegetable. Evening primrose oil is often used as a medicial or herbal supplement.

“That the petals do emit light on a dark night is not fanciful; still it is not due to a property of giving out spontaneous light (phosphorescence), but to a process of storing up sunlight during the day, and retaining it at night–a property identical with that exhibited by hepar sulphuris calcarea (calcined oyster shells), and the sulphides of barium and strontium.” ~ Millspaugh, American Medicinal Plants

Common O. biennis seeds are enjoyed by goldfinches.

During the Evening Primrose’s flowering season the flowers open at the rate of 2-4 per day, with a ‘zone of flowering’ gradually moving up the stem as the season progresses.

Some garden Oenathera are native to the US, some to Europe, and others seems to have questions as to which place can claim origination.

O. biennis seeds live for 39–40 years or longer in soil.

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Ilona Erwin, author

Meet the Author

Ilona Erwin

I started working on this website beginning in 1998, when it was part of Ilona's Reflecting Pool. Since then I've branched out into a number of online endeavors and work at writing lots of content for my sites. "Ilona's Garden" remains my primary site and is dedicated to home gardener's success.