Oenothera is a genus of about 145 species of herbaceous flowering plants native to the Americas. It is the type genus of the family Onagraceae. Common names include evening primrose, suncups, and sundrops. They are not closely related to the true primroses (genus Primula). The species vary in size from small alpine plants 10 centimeters tall, such... Found on http://en.wikipedia.org/wiki/Oenothera
Oenothera is a genus of herbs and shrubs of the family Onagrariaceae. They generally bear showy flowers, which commonly bloom at night, from which they get their popular name of 'evening primrose' . The flowers have four petals, obovate in form. Found on http://www.probertencyclopaedia.com/browse/BO.HTM