Each flower blooms for only one day and you can practically watch them open. They grow in sandy arid soils, roadside ditches, and rocky places. These plants grow in most of northern America, from Canada to Florida.
Evening Primrose was used by Native Americans for long before Europeans arrived as both a food and medicine. The European name if Evening Primrose refers to the one new flower that blooms along each stalk each evening. If you can find the plant, you can often observe that flower blooming within an hour or so. The plant blooms from Late June through late August. It is commonly mistaken for common Mullein due to Mullein's tall stalk of yellow flowers arising from it's base of leaves. Evening Primrose however has smooth leaves and multi stalks of flowers where as Mullein has fuzzy leaves and just one tall stalk.
Evening Primrose grows in hot dry sites and it's seeds are light dependent meaning it cannot germinate without sunlight on the seed. It also takes a few weeks to germinate so it often struggles to get enough sun in order to grow before weeds shade it out. Interestingly, the plant is an oil source as well, with each seed containing up to 10% oil. The oil is said to be a treatment for eczema and other skin irritations but all scientific testing has said it is not an effective treatment for any illness or disease.
Evening Primrose is currently used as an supplement and sold in capsules in the vitamin sections of most pharmacies. Native Americans from north to south used it to treat a variety of ailments and also ate all parts from the plant from root to flower to seeds. The roots, leaves, stalk, flower and seeds can all be eaten however there is no evidence that the plant has any health benefit.