Hooker’s Evening Primrose

Oenothera elata

field filled with tall stems and yellow flowers
Santa Inez trailhead | July 2012

Hooker’s evening primrose (Oenothera elata) is a tall, herbaceous plant in the evening primrose family (Onagraceae). It is characterized by its showy bright yellow flowers with four heart-shaped petals and by elongated seedpods that develop below the base of the petals.

As its name implies, Hooker’s evening primrose has nocturnal flowers that open in the evening and wither the following morning. It is primarily pollinated at night by sphinx moth, but may be visited by other insects near dawn and dusk.

Hooker’s evening primrose is native to California. However, it is also found elsewhere in western North America, growing along streams and in moist places in many plant communities.

Other Common Names:

Hairy evening primrose, western evening primrose, marsh evening primrose

Description 2,4,11,26,59

Hooker’s evening primrose is a tall herbaceous plant with one or more upright, unbranched stems, often less than 6 ft. (2 m) long, although there are plants in the East Basin that have reached ten feet (3 m).
Hooker’s evening primrose is usually biennial, completing its life cycle in two growing seasons. The first year, it produces a large fleshy taproot and a basal rosette of leaves. Flowers and fruits are produced during the second year of growth. In our region, it may be a short-lived perennial, flowering for more than one year.
Leaves in the basal rosette are 12 inches (30 cm long), usually widest toward the outer end and acute at the tip. From the basal rosette emerge stout, reddish stems, which are covered with short, soft hairs. Stem leaves look like tongues and are somewhat smaller than those in the rosette. They lack a petiole and clasp the stem directly, growing in a spiral around it.
The main blooming period of Hooker’s evening primrose occurs from ay through September,1 but isolated flowers may be produced throughout the year. They are found singly along the stem, opening sequentially from the bottom upward. Only one to a few flowers are in bloom at any one time. They open at dusk and wither early the following day. Hooker’s evening primrose produces showy yellow flowers that are 3 inches (8 cm) across and turn orange with age. They are radially symmetrical with four heart-shaped petals and four smaller sepals that fold back away from the petals, often fused in pairs. The flowers are bisexual, with eight stamens and one pistil with an X-shaped stigma, that extends beyond the petals and stamens. The ovary is below the flower (it is “inferior”).
The maturing fruits are cylindrical green capsules that turn woody when mature, splitting lengthwise to release tiny angled seeds that ripen from late summer into fall.
yellow flower in the sun

Photo credit: Lea Corkidi | La Orilla trailhead | September

dried out stem

Opened seed pods | Santa Carina | November 2014

red branch with green leaves extending and flower not yet bloomed

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

Distribution 7

Hooker’s evening primrose is native to California but it is found elsewhere in western North America, typically growing in moist areas in a variety of vegetation types below 9500 feet (2950 m). It is also a common plant in disturbed areas along roads.

In the Reserve, Hooker’s evening primrose is often found along the lower trails. A large clump grows in the low area between Santa Inez and Santa Carina trailheads, often accompanied by a small cloud of hungry Goldfinches.

ariel view of conservancy

Classification 2,44

Hooker’s evening primrose is a dicot angiosperm in the Evening Primrose family (Onagraceae), which includes 657 species and 22 genera of trees, shrubs, and herbs.
Plants in this family are characterized by radial, bisexual, showy flowers with parts in multiples of 4 (4 petals, 4 sepals, and 8 stamens).143 Although the common name of the family (Evening Primrose), suggests that plant blooms at night, this applies primarily to members of the genus Oenothera. Other species on the Evening Primrose family in the reserve include Beach Primrose(Camissoniopsis cheiranthifolia), Lewis’ evening-primrose (C. lewsii) and canyon clarkia (Clarkia epilobioides).48
The genus Oenothera has 145 species, which are distinguished by having ovaries and fruits below the flowers (inferior ovaries) and by stigmas in the shape of a cross.
Changing taxonomy has left a long string of synonyms for our species, especially at the subspecies or varietal level.6783 There are three currently recognized subspecies of Oenothera elata but only two occur in California. Ours is ssp hirsutissima, the other is ssp. hookerii. Either subspecies may be called evening primrose or Hooker’s evening primrose.
Alternate Scientific Names:

Oenothera biennis, Oenothera hookeri, Oenothera ornata, Oenothera simsiana

Jepson eFlora Taxon Page
yellow flower with 4 petals

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

close up of yellow flower with 4 double sided petals

Photo credit: Lea Corkidi | La Orilla | September 2014

Two yellow flowers on one stem

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

Ecology

Flowers of Hooker’s evening primrose open at night and have most of the characteristics associated with night-pollination by moths: they are large with nectar glands in the bottom of a deep flower cup, and their reproductive parts extend beyond the petals. The pale flowers of Hooker’s evening primrose are visible to night-pollinators; they are also sweetly scented as an additional guide at night. Pollinators brush against the reproductive structures when they go into the base of the flower after nectar.
Hooker’s evening primrose are often pollinated by hawkmoths, particularly the white-lined sphinx moth (Hyles lineata), and by bees active at dawn and dusk such as the twilight-foraging carpenter bee (Xylocopa tabaniformis) which gathers the pollen rather than nectar.156
This video of an unfurling blossom concludes with a visit by a white-lined sphinx moth.
Another conspicuous night-pollinated flower in the Reserve is the sacred Datura (Datura wrightii), also pollinated by the white-lined Sphinx moth.
The seeds of Hooker’s evening primrose are an important food source for Lesser Goldfinch.
yellow flowers on a stem

Photo credit: Barbara Wallach | Nature Center | May 2013

small green plant with many leaves on ground

La Orilla trailhead | November 2014

Bird hanging on dried out brown branch

Lesser Goldfinch eating seeds | Photo credit: Jo Quinn | San Andres Dr. trailhead | July 2015

Human Uses

Evening primrose has edible leaves, seedpods, and roots.112 Some may object to the mucilaginous texture of the root system, but it is one the few widespread wild root vegetables of the west.34

The seeds of Oenothera elata ssp. hirsutissima produce an oil that is said to reduce inflammation and is used in soaps and pharmaceuticals.83 They can also be a good source of gamma-linoleic acid, an essential oil in high demand in the pharmaceutical and nutritional industries.157, 158
Hooker’s evening primrose is moderately tolerant to salinity, so it has been suggested as an ornamental plant for landscapes irrigated with reclaimed water.159
brown dried out branch

Opened seed pods | Santa Carina | November 2014

field with tall stems and single yellow flower on each

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

yellow flower with 4 petals

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

Interesting Facts

The genus name,Oenothera comes from the greek term meaning wine-scented , and elata comes from the latin word elatus, meaning elevated.

yellow flowers on top of stems

Photo credit: Lea Corkidi | La Orilla | September 2014

close up of yellow flower with 4 petals

Photo credit: Lea Corkidi | La Orilla | September 2014

side view of 4 petal yellow flower

Photo credit: Lea Corkidi | La Orilla trailhead | September 2014

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