Southwest Colorado Wildflowers, Oenothera flava and longissima

Linnaeus named this genus in 1753 using a name given several thousand years ago by Theophrastus to another genus in this family. The meaning of "Oenothera" is not agreed on; Greek gives us both "oenos" for "wine" and "thera" which is variously translated as "to seek", "to imbibe", "to catch", "to hunt". "Thera" could indicate that the plant (really just the root) was used to flavor wine, or the root was used to absorb wine and was then fed to animals to calm them, or the juice of the root was put in wine to seduce, or the root in wine just plain made people happy.

See more yellow Oenotheras and white Oenotheras.

Oenothera flava subspecies flava (Yellow Evening Primrose)
Onagraceae (Evening Primrose Family)

Foothills, montane. Openings, meadows. Spring, summer.
Lizard Head Trail, June 19, 2004.

Oenothera flava flowers are one-and-a half to two inches across and so bright that they always catch attention. The long pink flower tube is usually overlooked. Flowers open late in the day and wilt to a gnarled pink mass (see center and bottom of picture) early the next day. Oenothera flava likes moist areas and it grows there with an abundance of dark green, wavy-edged leaves.

Marcus Jones collected the first specimen of this plant in 1894 in Utah and the plant was first named Oenothera triloba variety ecristata by Aven Nelson in 1895. It was renamed Oenothera flava in 1927 by Albert Garrett. "Flava" is Latin for "yellow".

Oenothera flava subspecies flava (Yellow Evening Primrose)
Onagraceae (Evening Primrose Family)

Foothills, montane. Openings, meadows. Spring, summer.
Navajo Lake Trail, July 11, 2005.

Oenothera longissima (Bridges Evening Primrose)
Onagraceae (Evening Primrose Family)

Semi-desert. Washes, roadsides, sand. Summer, fall.
Hunter Canyon, Utah, September 26, 2005 and Comb Ridge, Utah, October 19, 2016.

Oenothera longissima grabs and holds your attention with its large and brilliant yellow flowers, with its size -- commonly four-to-six feet tall and sometimes to 10 feet, and certainly with its striking four-to six inch long hypanthium, the tube formed by the fusion of the bases of the stamens, petals, and sepals. (In the photograph at left, the hypanthium is the long tube just below each flower.) But at the same time it is easy to pass by Oenothera longissima because it often grows with other thick vegetation and because its leaves are quite Willow-like it is easy to mistake it for one of the many Willows in our area. Of course, once it flowers, the resemblance to Willows is gone.

Look for Oenothera longissima in sandy washes and other riparian areas and even in wet depressions on slick rock, as in this late season photograph:

Oenothera longissima

O. elata is similar to O. longissima. The flowers of each species are about the same size so a good way to distinguish between the two species is to observe the relative size of the flowers to the hypanthium in each species. The sepals and petals of O. elata are about the same length as the hypanthium; the sepals and petals of O. longissima are about the same size as those of O. elata but the hypanthium is typically two-to-three times as long. Also, as the range maps for each species indicate, O. elata is far more widely distributed than O. longissima, and although the elevational ranges of the two species does overlap, O. elata is also found at higher elevations along forest roads.

In 1911 Per Axel Rydberg was the first to collect this plant for science. He found it in the Natural Bridges area of Utah (hence, "Bridges Evening Primrose") and he named and described it in 1913.

Oenothera longissima (Bridges Evening Primrose)
Onagraceae (Evening Primrose Family)

Semi-desert. Washes, roadsides, sand. Summer, fall.
Hunter Canyon, Utah, September 26, 2005.

The large, showy, yellow flowers and the very long hypanthiums are diagnostic.

Oenothera longissima (Bridges Evening Primrose)
Onagraceae (Evening Primrose Family)

Semi-desert. Washes, roadsides, sand. Summer, fall.
Near Bluff, Utah, September 2, 2007.

In the photographs above, you can see that Oenothera longissima has widely spaced stem leaves, but as shown at left, basal leaves are massed.

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Oenothera flava

Range map for Oenothera longissima