The Genus Oenothera
Evening Primroses, Sundrops, Gaura
Family: Onagraceae
The genus Oenothera includes a bunch of popular plants in our region. There are 167 species in total in the Americas. They have been introduced all over the world now. They are herbaceous annuals and perennials (we only talk about the perennials here). Almost all of them are nocturnal flowering—opening in the late afternoon/early evening and blooming all night until late morning. Many have wonderful frangrances. This genus is important to moths as nectar sources and as larval hosts.
Evening primroses are favorite plant foods for tortoises.
The genus name Oenothera comes from the Greek oinos, wine, and therao, to seek or imbibe. One story suggests that when the root was eaten, it allowed a person to drink a greater quantity of wine. It has also been suggested that evening primrose (specifically Oenothera biennis) has been used to flavor wine.
Photo of Oenothera elata by Patrick Alexander, SEINET
Oenothera caespitosa
Tufted Evening Primrose
Perennial plant growing about a foot high and sometimes spreading up to 3’ wide. White flowers open at dusk and stay open until morning. Woody capsules with seeds form within the foliage. Plants are perennial, but if they lack resources (water, nutrition) they’ll act as annuals and die back, leaving behind their woody capsules that are often found in the desert, puzzling those who find them. These plants reseed very well and will form colonies. In the low desert these plants are evergreen, but leaves will take on shades of red in response to cold (it’s quite pretty).
Grow in full to part sun, provide moderate water and good drainage. Plants are hardy to -20° F.
Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). Granivorous birds like finches love the seeds. These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Tufted Evening Primrose is used as a dermatological aid (Blackfoot), a gynecological aid (Navajo, Kayenta) and as eye medicine (Hopi).
Oenothera comes from the Greek oinos, wine, and therao, to seek or imbibe; cespitosa means having a densely clumped, tufted or cushion-like growth form.
Found in a wide range of habitats, especially at open sites, from 3,000-7,500 ft. throughout most of the western and midwestern states; south into northern Mexico.
Oenothera elata
Hooker’s Evening Primrose
Herbaceous perennials that have the ability to get as much as 8’ tall but normally much, much shorter, on average 2-3’ tall (specimens that reach such heights are usually in regional wetlands). Yellow flowers occur in warm weather, opening at dusk and lasting until late morning the next day. Woody capsules follow the flowers held high up on the tall stems which allow seeds to be dispersed (often by birds). Plants colonize aggressively.
Full to part sun, or even bright shade, moderate to regular water, hardy to -10°F. Cut back long after seeds are gone.
Leave the dry seed heads linger so the goldfinches and other granivorous birds can use the seeds, they love them, especially held up high. Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Used as a ceremonial emetic, as a cold remedy, for sores, swellings, mumps, as a life medicine, as a yellow dye, as a good luck charm, and a means to repel snakes.
Oenothera is from Greek oinos, wine and thera, to imbibe, while elata means tall.
Formerly known as Oenothera hookeri, thus the common name Hooker’s evening primrose (“Hooker” after Joseph Dalton Hooker, a British botanist and explorer in the 19th century).
Found in along streams, in meadows, rocky slopes or scree, or in other distrubed habitats from 2,000-9,000 ft. throughout the western states of the United States, south into Mexico.
Photo by Petey Mesquitey at the ol’ guajolote
Oenothera hartwegii
Hartweg’s Sundrops
Herbaceous perennial growing to about 1’ tall and spreading 2’. Yellow flowers most of the warm season. Foliage turns reddish in cold weather.
Grow in full to part sun, moderate water, hardy to -15°F.
Larval food plant for the white lined sphinx moth (Hyles lineata), and flower moths (Schinia spp). Tortoises love this plant.
This plant is also known as Calylophus hartwegii.
Oenothera is from Greek oinos, wine and thera, to imbibe. The species hartwegii is named for the German plant collector Karl Theodor Hartweg (1812-1871).
Found in deserts, plains, and foothills, from 3,500-7,000 ft. in Arizona, New Mexico, Oklahoma and Texas, south into northern Mexico.
The following subspecies are accepted:
Oenothera hartwegii subsp. fendleri – Arizona, New Mexico, Kansas, Oklahoma, Texas, northeastern Mexico
Oenothera hartwegii subsp. filifolia – New Mexico, Texas, northeastern Mexico
Oenothera hartwegii subsp. hartwegii – Colorado, Texas, northern and western Mexico
Oenothera hartwegii subsp. maccartii – Texas, northeastern Mexico
Oenothera hartwegii subsp. pubescens – Arizona, New Mexico, Colorado, Kansas, Oklahoma, Texas, northeastern Mexico
Oenothera harwegii on iNaturalist
Photo by Sally and Andy Wasowski, Lady Bird Johnson Wildflower Center
Oenothera lindheimeri
Whirling Butterflies
Herbaceous perennial growing about 3x3’ and reseeding about the landscape. Flowers can be white to light pink, to almost red (depending on cultivar) and occur throughout the year, whenever the weather is warm enough. Plants reseed readily in the landscape.
Grow in full to part sun, provide regular water, and amended soil. Plants are hardy to -10° F. Cut back plants occasionally to encourage bushiness.
Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). Granivorous birds like finches love the seeds. These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Oenothera is from Greek oinos, wine and thera, to imbibe, while the specific epithet honors Ferdinand Jacob Lindheimer (1801-1879), Texas plant collector.
This plant was formerly known as Gaura lindheimeri, and commonly still called “gaura” by many people.
Found over a small area of south USA, in southeast Texas and southwest Louisiana, plus small areas of the Gulf states further east in woodland, grassland, and disturbed areas. A common garden perennial that has many horticultural selections.
Oenothera macrocarpa
Big Fruit Evening Primrose
This sometimes leathery-leaved perennial grows to a tidy 1’ high and about 1.5-2’ wide. Some cultivars have silver leaves. Fragrant yellow flowers occur in warm weather, opening up at dusk and lasting until late morning. Flowers are followed by enormous, pods with wings. Plants are evergreen or briefly deciduous in Tucson.
Full to part sun, moderate water in well-drained soil, hardy to -40°F.
Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). Granivorous birds like finches love the seeds. These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Dry seedpods are very cool looking and used in flower arrangements.
Oenothera is from Greek oinos, wine and thera, to imbibe, while macrocarpa means “big fruit” referring to the large, dry, 4-winged fruit.
Dry rocky barrens in calcareous soil; southern Illinois and Montana to Nebraska and Colorado, south to Texas.
Oenothera serrulata
Prairie Sundrops
Perennial plant growing to about a foot high, or lower, spreading about 2’. Yellow flowers most of the warm season. Foliage turns reddish in cold weather. Differs from the regularly available sundrops (Oenothera hartwegii) by having smaller, thinner leaves.
Grow in full to part sun, moderate water, hardy to 0°F.
Larval food plant for the white lined sphinx moth (Hyles lineata), and flower moths (Schinia spp). Loved by tortoises.
There is confusion about the taxonomy of this species. It could also be Oenothera berlandieri subsp pinifolia. This plant is most often found in the trade as Calylophus drummundianus, or Calylophus drummundii.
Oenothera is from Greek oinos, wine and thera, to imbibe. The species serrulata refers to the serrulate edges of the leaves.
This species is native to central North America, including central Canada and the central United States including in nearby New Mexico and Texas and south into adjacent Mexico. Found in dry grasslands and rocky outcrops.
Oenothera speciosa
Mexican Evening Primrose
Spreading perennial growing no taller than a foot and spreading at least 3’ if allowed to. This plant spreads by creeping rhizomes. Pink flowers occur throughout the warm season. Plants are mostly evergreen but cold weather will turn the foliage reddish. Plants reseed readily in the landscape.
Grow in full to part sun, provide moderate to regular water, hardy to -20° F. Cut back plants as needed. Lift and divide plants occasionally as this is a spreading rhizomatous plant.
Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). Granivorous birds like finches love the seeds. These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Oenothera is from Greek oinos, wine and thera, to imbibe, while speciosa means showy.
Dry rocky barrens in calcareous soil; southern Illinois and Montana to Nebraska and Colorado, south to Texas.
Oenothera stubbei
Nuevo Leon Evening Primrose
Very fast spreading perennial usually only a foot high but spreading 6’ or more. Yellow flowers occur in warm weather, open at night and bloom until late morning the next day. Plants are mostly evergreen.
Grow in full to part sun, regular water, hardy to about 10° F.
Larval food plants for white lined sphinx moth (Hyles lineata) and other sphinx moths, plus noctuid flower moths (genus: Schinia). Granivorous birds like finches love the seeds. These plants are visited by many, many pollinators. However, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Moths are the primary pollinators of this species. Desert tortoises love to eat the foliage and flowers of this plant.
Oenothera is from Greek oinos, wine and thera, to imbibe, while speciosa means showy.
Dry rocky barrens in calcareous soil; southern Illinois and Montana to Nebraska and Colorado, south to Texas.
From calcite slopes in Nuevo Leon.
Photo by Mountain States Wholesale Nursery who introduced the plant into the trade.