Oenothera is a Genus of about 125 species of annual

Annual plant

An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

, biennial

Biennial plant

A biennial plant is a flowering plant that takes two years to complete its biological lifecycle. In the first year the plant grows leaves, stems, and roots , then it enters a period of dormancy over the colder months. Usually the stem remains very short and the leaves are low to the ground, forming...

 and perennial

Perennial plant

A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

 herbaceous

Herbaceous

A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

 flowering plants, native to North and South America

Americas

The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

. It is the type genus

Type genus

In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

 of the family Onagraceae

Onagraceae

Onagraceae, also known as the Willowherb family or Evening Primrose family, are a family of flowering plants. The family includes about 640-650 species of herbs, shrubs, and trees in 20-24 genera...

, the Evening Primrose Family. Common names include evening-primrose, suncups, and sundrops.

The species vary in size from small alpine plants 10 cm tall (e.g. O. acaulis from Chile

Chile

Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

), to vigorous lowland species growing to 3 m (e.g. O. stubbei from Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

). The leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 form a basal rosette at ground level and spiral up to the flowering stems; the leaves are dentate or deeply lobed (pinnatifid). The flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s of many species open within less than a minute in the evening, hence the name "evening-primrose", and are yellow in most species but white, purple, pink or red in a few. Most native desert species are white. The fragrant tufted evening-primrose Oenothera caespitosa

Oenothera caespitosa

Oenothera caespitosa, known commonly as tufted evening primrose and fragrant evening primrose, is a perennial plant of the genus Oenothera native to much of western and central North America...

, a Southwestern species, first blooms white but turns pink or light magenta.

One of the most distinctive features of the flower is the stigma with four branches, forming an X shape. Pollination

Pollination

Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...

 is by Lepidoptera

Lepidoptera

Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

 (moths) and bee

Bee

Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...

s; like many members of the Onagraceae

Onagraceae

Onagraceae, also known as the Willowherb family or Evening Primrose family, are a family of flowering plants. The family includes about 640-650 species of herbs, shrubs, and trees in 20-24 genera...

, however, the pollen grains are loosely held together by viscin threads (see photo below), meaning that only bees that are morphologically specialized to gather this pollen can effectively pollinate the flowers (it cannot be held effectively in a typical bee scopa

Scopa (biology)

The term scopa is used to refer to any of a number of different modifications on the body of a non-parasitic bee that form a pollen-carrying apparatus. In most bees, the scopa is simply a particularly dense mass of elongated, often branched, hairs on the hind leg...

). Furthermore, the flowers are open at a time when most bee species are inactive, so the bees which visit Oenothera are also compelled to be vespertine

Vespertine (biology)

Vespertine is a term used in the life sciences to indicate something of, relating to, or occurring in the evening. In botany, a vespertine flower is one that opens or blooms in the evening. In zoology, the term is used for a creature that becomes active in the evening, such as bats and owls...

 temporal specialists. The seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s ripen from late summer to fall.

Oenothera species are used as food plants by the larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e of some Lepidoptera

Lepidoptera

Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

 species including Schinia felicitata

Schinia

Schinia, commonly called Flower Moths, is a large genus of moths belonging to the family Noctuidae. The genus has a Holarctic distribution with the vast majority of species being found in North America, many with a very restricted range and larval food plant.-Species Information and Food Plants:...

and Schinia florida

Schinia

Schinia, commonly called Flower Moths, is a large genus of moths belonging to the family Noctuidae. The genus has a Holarctic distribution with the vast majority of species being found in North America, many with a very restricted range and larval food plant.-Species Information and Food Plants:...

, both of which feed exclusively on the genus, the former exclusively on O. deltoides.

In the wild, evening-primrose acts as a primary colonizer, quickly appearing wherever a patch of bare ground may be found. It tends to germinate in disturbed soil, meaning that it tends to be found in poorer environments such as dune

Dune

In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

s, roadsides, railway embankments and wasteland. It often occurs as a casual, eventually being out-competed by other species.

Origin

The genus Oenothera may have originated in Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 and Central America

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

  from which it spread into North and South America and, with the advent of international travel, species are now found in most temperate regions. During the Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 era a succession of ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

s swept down across North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, with intervening warm periods. This was repeated for four ice ages, with four separate waves of colonization, each hybridizing with the remnants of the previous waves This generated a present-day group of species forming the subsection Euoenothera which is very rich in genetic diversity

Genetic diversity

Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....

, spread right across the North American continent. These species are morphologically diverse and are largely interfertile and so the species boundaries have been a source of dispute amongst taxonomists

Alpha taxonomy

Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...

.

This pattern of repeated colonizations resulted in a unique genetic conformation in the Euoenotherae whereby the chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

s at meiosis

Meiosis

Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....

 can form into circles of varying size, rather than complete chromosome pairing as in common meiosis. This is the result of several reciprocal translocations

Chromosomal translocation

In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...

 between chromosomes so that the pairing occurs only at the tips. This phenomenon has some apparently non-Mendelian

Mendelian inheritance

Mendelian inheritance is a scientific description of how hereditary characteristics are passed from parent organisms to their offspring; it underlies much of genetics...

 genetic consequences. By combining this mode of chromosome segregation with a system of balanced-lethal genes

Gene lethality

Gene lethality occurs when two individuals of the same phenotype mate and a 2:1 phenotypic ratio exists in the offspring . Usually the homozygous dominant individuals will have been aborted before birth....

, genetic recombination

Genetic recombination

Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...

 is prevented and the plants enjoy the vigour of heterosis

Heterosis

Heterosis, or hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. The adjective derived from heterosis is heterotic....

. This resulted in the evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

  of a large number of sympatric races over North America, east of the Rocky Mountains

Rocky Mountains

The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...

. Analysis of the cytology

Cell biology

Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...

 of these races and of artificial hybrids between them allowed a detailed understanding of the genetic and geographic evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 of the Euoenotherae. This whole subject was a major area of genetic research during the first half of the 20th century.

Taxonomy

Evening-primrose was originally assigned to the genus Onagra, which gave the family Onagraceae its name. Onagra (meaning "(food of) onager

Onager

The Onager is a large member of the genus Equus of the family Equidae native to the deserts of Syria, Iran, Pakistan, India, Israel and Tibet...

") was first used in botany

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

 in 1587, and in English in Philip Miller

Philip Miller

Philip Miller FRS was a Scottish botanist.Miller was chief gardener at the Chelsea Physic Garden from 1722 until he was pressured to retire shortly before his death...

's 1754 Gardeners Dictionary: Abridged. Its modern name Oenothera was published by Carolus Linnaeus

Carolus Linnaeus

Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...

 in his Systema Naturae

Systema Naturae

The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...

. Its etymology is uncertain but is believed to be derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 words ονος θηρας (onos theras), meaning "donkey catcher," or οινος θηρας (oinos theras), meaning "wine seeker." In addition, oenothera means "a plant whose juices may cause sleep" in Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

.

In 1905, while studying the genetics of Oenothera lamarckiana, Hugo de Vries

Hugo de Vries

Hugo Marie de Vries ForMemRS was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation...

 discovered a variant with a chromosome number of 2N = 28 compared with 2n = 14 for O. lamarckiana. DeVries was unable to breed this variant with O. lamarckiana. He named the variant Oenothera gigas.

Uses

Young root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s can be eaten like a vegetable (with a peppery

Black pepper

Black pepper is a flowering vine in the family Piperaceae, cultivated for its fruit, which is usually dried and used as a spice and seasoning. The fruit, known as a peppercorn when dried, is approximately in diameter, dark red when fully mature, and, like all drupes, contains a single seed...

 flavor), or the shoots can be eaten as a salad

Salad

Salad is any of a wide variety of dishes, including vegetable salads; salads of pasta, legumes, eggs, or grains; mixed salads incorporating meat, poultry, or seafood; and fruit salads. They may include a mixture of cold and hot, often including raw vegetables or fruits.Green salads include leaf...

. Poultices containing O. biennis were at one time used to ease bruise

Bruise

A bruise, also called a contusion, is a type of relatively minor hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep into the surrounding interstitial tissues. Bruises can involve capillaries at the level of skin, subcutaneous tissue, muscle,...

s and speed wound

Wound

A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...

 healing. One of the common names for Oenothera, "Kings cureall", reflects the wide range of healing powers ascribed to this plant, although it should be noted that its efficacy for these purposes has not been demonstrated in clinical trials.

The mature seeds contain approximately 7-10% gamma-linolenic acid

Gamma-Linolenic acid

γ-Linolenic acid is a fatty acid found primarily in vegetable oils...

, a fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

. The oil also contains around 70% linoleic acid

Linoleic acid

Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...

. The O. biennis seed oil is used to reduce the pains of premenstrual stress syndrome

Premenstrual stress syndrome

Premenstrual syndrome is a collection of physical and emotional symptoms related to a woman's menstrual cycle...

. Gamma-linolenic acid also shows promise against breast cancer. Some side effects of using evening primrose oil are itching, sore throat and severe or extreme gassiness.

Cultivation

A number of perennial members of the genus are commonly cultivated and used in Southwestern U.S. landscapes. The more popular species include Oenothera caespitosa

Oenothera caespitosa

Oenothera caespitosa, known commonly as tufted evening primrose and fragrant evening primrose, is a perennial plant of the genus Oenothera native to much of western and central North America...

, the tufted evening primrose, Oenothera berlanderii, the Mexican evening primrose, and Oenothera stubbei the Saltillo primrose.

Annual evening-primroses are very popular ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s in gardens. For best growth, the seeds can be sown

Sowing

Sowing is the process of planting seeds.-Plants which are usually sown:Among the major field crops, oats, wheat, and rye are sowed, grasses and legumes are seeded, and maize and soybeans are planted...

 in situ. In temperate climates, planting should be from late spring to early summer. Some species grow successfully in fertile soils if competing species are kept at bay. Some evening-primrose species can be planted in any ordinary, dry, well-drained garden soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 (preferably sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

y loam

Loam

Loam is soil composed of sand, silt, and clay in relatively even concentration . Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils...

) in an open site that is sunny to partly shady. Many are fairly drought

Drought

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

-resistant.

The first plants to arrive in Europe reached Padua

Padua

Padua is a city and comune in the Veneto, northern Italy. It is the capital of the province of Padua and the economic and communications hub of the area. Padua's population is 212,500 . The city is sometimes included, with Venice and Treviso, in the Padua-Treviso-Venice Metropolitan Area, having...

 from Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

 in 1614 and were described by the English botanist John Goodyer

John Goodyer

John Goodyer was a 17th century botanist who lived in Hampshire, England. He was born in Alton, and evidently received a good education, although it is not known where...

 in 1621. Some species are now also naturalized

Naturalisation (biology)

In biology, naturalisation is any process by which a non-native organism spreads into the wild and its reproduction is sufficient to maintain its population. Such populations are said to be naturalised....

 in parts of Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, and can be grown as far north as 65° N in Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

. The UK National Council for the Conservation of Plants and Gardens, based at Wisley

Wisley

Wisley is a small village in Surrey, England. It lies between Cobham and Woking. It is the home of the Royal Horticultural Society's Wisley Garden. The River Wey runs through the village....

, maintains an Oenothera collection as part of its National Collections scheme.

External links

• Classification of the Evening Primrose Family at the Smithsonian Institution
• Details from A Modern Herbal, by Mrs M Greives at Botanical.com
• Plants For A Future
• "The evening primrose" A poem by John Clare
  John Clare
  John Clare was an English poet, born the son of a farm labourer who came to be known for his celebratory representations of the English countryside and his lamentation of its disruption. His poetry underwent a major re-evaluation in the late 20th century and he is often now considered to be among...
  
  
• Oenothera Biennis
• Oenothera Drummondii
• Oenothera Fruticosa
• Oenothera Speciosa