Photo by Melody

PlantFiles: Evening Primrose, Dandelion-leaved Sundrop
Oenothera acaulis

Family: Onagraceae (on-uh-GRAY-see-ee) (Info)
Genus: Oenothera (ee-no-THEE-ruh) (Info)
Species: acaulis (a-KAW-liss) (Info)

One vendor has this plant for sale.

2 members have or want this plant for trade.


6-12 in. (15-30 cm)

6-9 in. (15-22 cm)

USDA Zone 5a: to -28.8 C (-20 F)
USDA Zone 5b: to -26.1 C (-15 F)
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)

Sun Exposure:
Sun to Partial Shade

Unknown - Tell us

Bloom Color:
Pale Yellow

Bloom Time:
Mid Summer
Late Summer/Early Fall
Blooms repeatedly


Other details:
Average Water Needs; Water regularly; do not overwater

Soil pH requirements:
Unknown - Tell us

Patent Information:
Unknown - Tell us

Propagation Methods:
From seed; direct sow outdoors in fall

Seed Collecting:
Allow pods to dry on plant; break open to collect seeds

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There are a total of 10 photos.
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7 positives
No neutrals
No negatives

Gardeners' Notes:

Positive John_Riley On Aug 13, 2011, John_Riley from Markham
Canada wrote:

We are in Markham, Ontario, Canada. We have a few of these plants and only now have discovered it's actual name. Thanks for including nine o'clock in the description.
Our stories would be the same as all the others, including gatherings in our yard at dusk. I have a video of the opening if i am able to upload.

Positive rsohps On Aug 13, 2004, rsohps from Murrysville, PA wrote:

Watching these bloom at about 9 pm is like watching time lapse photography. They attract hummingbird moths in the evening. DO NOT mulch. I lost almost all of mine due to mulch. Reliably hardy in Zone 5 near Pittsburgh, since I've had mine for at least 10 years.

Positive cdb On Jul 12, 2004, cdb from Lake Mills, WI wrote:

This plant has been the cause of many evening gatherings in our garden. Bloom time is quite dramatic and we've even been known to cheer as the flowers open! I'll add as a beginning gardener the evening primrose is not difficult to grow.

Positive snowtrillium On Jun 18, 2004, snowtrillium from London
Canada wrote:

To cllect seed from this plant -
In september/October after blooming is finished, look under the leaves at the base of the plant and gather the seed pods.
Dry and store ,or open the pods and sprinkle where wanted.

To transplant seedlings or mature plants-
overcast/rainy day dig and keep as much soil on the root as possible
It will go into severe shock.
Plant and keep shaded untill shock wears off.

Positive ambest On Jun 5, 2004, ambest from Riverside, CA wrote:

This is my second yr. of the beautiful evening primrose. Here in Ca., it opens up around 5p.m., and mine are in partial shade, so they remain open til around noon. This yr. I will be getting lots of seeds, I recommmend this plant to anyone who enjoys beauty and the smell is outstanding. Mine are planted with pink valerian, lavender, morning glories, sea lavender,and pink sage, also pretty white yarrow. It makes a very beautiful and fragrant garden....enjoy!

Positive JenniesWorld On Apr 5, 2004, JenniesWorld from Spencer, WV wrote:

The Evening Primrose, also called Nine-O-Clock in West Virginia, is an intriguing plant. The opening of the flowers at precisely nine p.m. (Daylight Savings Time) is a magical experience. First, the petals begin to tremble, then as the petals begin to seperate the bud is vaselike, but as the petals expand the flower snaps open to reveal a creamy yellow center. The Hummingbird Moths, fairly rare here, thrive on the nectar and they are as fascinating to watch as the flower-bud opening is!
This is the plant from which they extract Evening Primrose Oil, high in bebeficial GLAs.

Positive VeganGurl20 On Nov 18, 2003, VeganGurl20 from Tulsa, OK wrote:

This plant is easy to grow, attractive, and makes lots of beautiful, sweet smelling flowers. I thoroughly enjoy this plant!


This plant has been said to grow in the following regions:

Riverside, California
Chicago, Illinois
Patriot, Indiana
Lincoln Park, Michigan
Akron, New York
Buffalo, New York
Penn Yan, New York
Rochester, New York
Watertown, New York
Cleveland, Ohio
Tulsa, Oklahoma
Philadelphia, Pennsylvania
Trafford, Pennsylvania
Austin, Texas
Sterling, Virginia
Lake Mills, Wisconsin

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