Oenothera biennis, the common evening-primrose, is a species of flowering plant in the family Onagraceae, native to eastern and central North America, from Newfoundland west to Alberta, southeast to Florida, and southwest to Texas, and widely naturalized elsewhere in temperate and subtropical regions. Evening primrose oil is produced from the plant.
Common names The plant is known by various common names, such as evening star, sundrop, German rampion, hog weed, and fever-plant.
Description
Oenothera biennis usually has a life span of two years (biennial) growing to tall in the seeding year. The leaves are lanceolate, long and wide, produced in a tight rosette the first year, and spirally on a stem the second year. However, plants with annual life cycles are documented, and have been selected for under experimental conditions in environments with low competition.
Growing cycle Most commonly, O. biennis grows as a low, spreading herb in the first year, just a few centimetres tall, with its leaves spreading out in a rosette to cover the ground, whilst storing energy in a thick root. In the second year, it grows up much taller, to around tall, on a semi-woody stem, which then flowers and seeds. This will usually die at first frosts, but occasionally grows another stem in the third year.
Blooming and fruiting Blooming lasts from late spring to late summer. The flowers are hermaphrodite, produced on a tall spike and only last until the following noon. They open visibly fast every evening producing an interesting spectacle, hence the name "evening primrose".
The blooms are yellow, diameter, with four bilobed petals. The flower structure has a bright nectar guide pattern, invisible to the naked eye. This pattern is apparent under ultraviolet light and visible to its pollinators, moths, butterflies, and bees.
The fruit is a capsule long and broad, containing numerous long seeds, released when the capsule splits into four sections at maturity.Borealforest: Oenothera biennis Plants of British Columbia: Oenothera biennis Jepson Flora: Oenothera biennis Ultraviolet Flowers: Oenothera biennis
Taxonomy Oenothera biennis was given its scientific name in 1753 by Carl Linnaeus in the book Species Plantarum. It has no accepted subspecies or varieties, but it has synonyms according to Plants of the World Online.
Table of SynonymsNameYearRankNotes Brunyera biennis 1899 species ≡ hom. Oenothera beckeri 1942 species = het., without a Latin descr. Oenothera biennis var. alba 1866 variety = het. Oenothera biennis var. angustifolia 1956 variety = het. Oenothera biennis subsp. biennis 1912 subspecies = het., not validly publ. Oenothera biennis subsp. caeciarum 1965 subspecies = het. Oenothera biennis var. cantabrigiana 1957 variety = het. Oenothera biennis subsp. centralis 1965 subspecies = het. Oenothera biennis subsp. chicaginensis 1961 subspecies = het. Oenothera biennis subsp. grandiflora 1948 subspecies = het., nom. superfl. Oenothera biennis subf. latifolia 1912 subform = het. Oenothera biennis f. leptomeres 2009 form = het. Oenothera biennis var. leptomeres 1914 variety = het. Oenothera biennis var. lutea 1866 variety = het. Oenothera biennis f. muricata 1912 form = het. Oenothera biennis var. muricata 1840 variety = het. Oenothera biennis f. nanella 1913 form = het. Oenothera biennis var. parviflora 1898 variety = het., nom. illeg. Oenothera biennis var. pycnocarpa 1924 variety = het. Oenothera biennis subsp. rubricaulis 1948 subspecies = het., nom. illeg. Oenothera biennis var. rubricaulis 1923 variety = het. Oenothera biennis subsp. suaveolens 1901 subspecies = het. Oenothera biennis var. sulphurea 1913 variety = het. Oenothera biennis var. vulgaris 1840 variety ≡ hom., not validly publ. Oenothera brevicapsula 1914 species = het. Oenothera brevispicata 1968 species = het. Oenothera cambrica 1977 species = het. Oenothera cambrica var. impunctata 1977 variety = het. Oenothera carinthiaca 1977 species = het. Oenothera casimiri 2004 species = het. Oenothera chicaginensis 1933 species = het. Oenothera chicaginensis var. bartlettii 1992 variety = het. Oenothera chicaginensis var. minutiflora 1979 variety = het. Oenothera chicaginensis var. parviflora 1956 variety = het. Oenothera chicagoensis 1930 species = het. Oenothera communis 1909 species = het., nom. superfl. Oenothera communis proles biennis 1910 proles ≡ hom. Oenothera communis f. canescens 1909 form = het. Oenothera communis f. suaveolens 1909 form = het. Oenothera compacta 1968 species = het. Oenothera editicaulis 1968 species = het. Oenothera ersteinensis 1970 species = het. Oenothera flaemingina 1968 species = het. Oenothera furca 1924 species = het. Oenothera gauroides 1813 species = het. Oenothera gauroides var. brevicapsula 1957 variety = het. Oenothera glabra 1768 species = het. Oenothera grandiflora var. tracyi 1957 variety = het. Oenothera grandifolia 1936 species = het. Oenothera graveolens 1782 species = het., opus utique oppr. Oenothera hirtella 1903 species = het., nom. illeg. Oenothera inconspecta 1968 species = het. Oenothera indivisa 1968 species = het. Oenothera jueterbogensis 1968 species = het. Oenothera jueterbogensis var. macrosperma 1964 variety = het. Oenothera latipetala 2010 species = het. Oenothera macrosperma 1965 species = het. Oenothera marinellae 1982 species = het. Oenothera media 1821 species = het. Oenothera mediomarchica 1968 species = het. Oenothera muricata 1767 species = het., nom. utique rej. prop. Oenothera muricata var. latifolia 1860 variety = het. Oenothera muricata var. rhodoneura 1937 variety = het. Oenothera muricata var. rubricaulis 1923 variety = het. Oenothera nissensis 1965 species = het. Oenothera nissensis var. fiedleri 1981 variety = het. Oenothera novae-scotiae var. serratifolia 1936 variety = het. Oenothera nuda 2009 species = het. Oenothera numismatica 1914 species = het. Oenothera obscurifolia 1968 species = het. Oenothera octolineata 1968 species = het. Oenothera paradoxa 1968 species = het. Oenothera paralamarckiana 1936 species = het. Oenothera parviflora var. muricata 1923 variety = het. Oenothera pedemontana 1983 species = het. Oenothera pellegrinii 1982 species = het. Oenothera pratincola 1914 species = het. Oenothera pratincola var. numismatica 1957 variety = het. Oenothera pratincola f. typica 1915 form = het., not validly publ. Oenothera pubescens 1841 species = het., nom. illeg. Oenothera punctulata 1971 species = het. Oenothera purpurata 1925 species = het. Oenothera pycnocarpa 1913 species = het. Oenothera pycnocarpa var. cleistogama 1936 variety = het. Oenothera pycnocarpa var. parviflora 1936 variety = het. Oenothera pyramidiflora 1968 species = het. Oenothera reynoldsii 1914 species = het. Oenothera reynoldsii f. semialta 1915 form = het. Oenothera reynoldsii f. typica 1915 form = het., not validly publ. Oenothera rostanskii 1985 species = het. Oenothera royfraseri 1936 species = het. Oenothera rubiella 1903 species = het. Oenothera rubiennis 1903 species = het. Oenothera rubricaulis 1913 species = het. Oenothera rubricaulis var. dentifolia 1979 variety = het. Oenothera rubricaulis var. longistylis 1981 variety = het. Oenothera rubricauloides 2007 species = het. Oenothera ruderalis 1914 species = het. Oenothera sabulosa 1930 species = het. Oenothera sackvillensis 1936 species = het. Oenothera sackvillensis var. albiviridis 1936 variety = het. Oenothera sackvillensis var. royfraseri 1957 variety = het. Oenothera salicastrum 1913 species = het. Oenothera sesitensis 1978 species = het. Oenothera shulliana 1931 species = het. Oenothera stenomeres 1914 species = het. Oenothera stenomeres f. typica 1915 form = het., not validly publ. Oenothera stucchii 1978 species = het. Oenothera suaveolens 1804 species = het. Oenothera suaveolens var. latipetala 1981 variety = het. Oenothera tacikii 1965 species = het. Oenothera tracyi 1911 species = het. Oenothera turoviensis 1965 species = het. Oenothera victorinii 1933 species = het. Oenothera victorinii var. intermedia 1936 variety = het. Oenothera victorinii var. parviflora 1936 variety = het. Oenothera victorinii f. rostanskii 1995 form = het. Oenothera victorinii var. undulata 1936 variety = het. Oenothera wratislaviensis 2007 species = het. Onagra biennis 1771 species ≡ hom. Onagra chrysantha var. latifolia 1835 variety = het. Onagra europaea 1835 species = het. Onagra media 1835 species = het. Onagra muricata 1794 species = het. Onagra vulgaris 1835 species = het. Onosuris acuminata 1817 species = het. Pseudo-oenothera virginiana 1860 species ≡ hom., nom. superfl. Notes: ≡ homotypic synonym; = heterotypic synonym
Ecology This plant is a weedy species that favors disturbed environments. It has been introduced and become established on all continents except Antarctica.
The seeds of the plant are important food for birds, including American goldfinch, Northern bobwhite, and mourning dove, and it is a larval host for both the primrose moth and the white-lined sphinx moth.The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press. Bumblebees and honeybees also visit the flowers.
The primrose moth (Schinia florida) is a common consumer of Oenothera biennis. The adults lay eggs on the flower, and the emerging caterpillars feed on the plant.
The seeds of O. biennis can remain viable in the soil seed bank for 70 years or more.
Uses
Over the centuries, Indigenous people in North America have used the plant as food and traditional medicine.
The evening primrose was introduced to Europe in the early 17th century as an ornamental plant in botanical gardens where its flowers are favored for nectar by pollinators, such as bees, and its seeds are food for birds.
Food uses Most of the plant parts are edible, having a taste that is mild. The roots can be eaten raw or cooked like potatoes. The leaves can be eaten raw in salads or cooked like spinach or in soups. Anishinaabe tribes traditionally make tea from the evening primrose leaves for use as a dietary aid and to reduce fatigue.
The flowering stems are preferably used when they are still young in June. They have to be peeled and can then be eaten raw or fried. The flower buds are regarded as a delicacy and can be harvested from June to October.
The seeds have a protein content of about 15%, an oil content of 24%, and contain about 43% cellulose. The proteins are especially rich in the sulphur-containing amino acids, methionine and cysteine, and tryptophan. Gamma-linolenic acid (GLA), and linoleic acid are present. Mainly for these polyunsaturated fatty acids, evening primrose oil is sold as a dietary supplement.
Research
There is not enough clinical evidence to support the use of evening primrose oil as a therapy for any medical condition. A Cochrane review concluded that there was no effect of primrose oil on eczema. The Mayo Clinic stated there was no good evidence that it affected eczema, diabetic neuropathy or premenstrual syndrome.
The American Cancer Society stated that there was little evidence for its effectiveness as an anti-cancer agent, for which it is sometimes promoted, and "neither GLA nor other GLA-rich supplements (such as evening primrose oil) have been convincingly shown to be useful in preventing or treating any other health conditions."
Adverse effects Evening primrose oil is considered likely as safe in recommended doses. It may increase the risk of bleeding, a concern for patients with bleeding disorders or taking drugs that may increase bleeding. The Mayo Clinic recommends caution in people with seizure disorders or mania, and by pregnant or breastfeeding women, and publishes a long list of possible side-effects. Oral use of evening primrose oil may cause headaches or nausea.
Traditional medicine The leaves and stems were used by Native Americans to treat skin, digestion, and throat conditions.
Agricultural practices