The wildflower Evening Primrose, Oenothera macrocarpa is also called Ozark Sundrops. The Great Plains Nature Center site says that pollination is provided by large hawkmoths and possibly hummingbirds.
The flowers have a distinctive, large X-shaped pistil which projects beyond the stamens.
GPNC site also says
Evening Primrose is a complex of four similar subspecies which occur in the southern half of the Great Plains.
1. Fremont's Evening Primrose (subsp. fremontii) - found in chalk badlands and rocky hillsides in northwest and north central Kansas and four counties in Nebraska. Formerly considered a separate species, it has smaller flowers and shorter wings on its seed pods than the other three.
2. Hoary Evening Primrose (subsp. incana) - found from southwestern Kansas to the Oklahoma and Texas panhandles. Hoary Evening Primrose is densely covered with short hairs.
3. Oklahoma Evening Primrose (subsp. oklahomensis) - found from the Gyp Hills of south central Kansas south into Texas. This subspecies is the only one that is completely hairless.
4. Missouri Evening Primrose (subsp. macrocarpa) - widely distributed from central Texas through Oklahoma and eastern Kansas to southeast Nebraska. It is also found in limestone glades in the Ozark Mountain region of Missouri and Arkansas. This has the largest flowers and seed pods of any of the four.
The seed pod of this species is very distinctive. It has four papery wings on it that allow the pod to be blown about by the wind, helping to scatter the seeds.
My plant is taller than me, not a low to the ground sprawler. Oenothera glazioviana Tina James is the variety, a biennial like the rest. I found out about this variety through Cindy Cope and the Botanical Garden of Northwest Arkansas. I started the seeds about 18 months ago and it is blooming now for the first time.
Unlike other plants with flowers that bloom only one day, evening primrose is at its prime when we have coffee outside early in the morning. By afternoon, those blooms are gone. The next day, new blossoms appear.
At the Vanderbilt University site, "It is believed that the Indians taught the pilgrims about the medicinal benefits of evening primrose and then it was quickly exported to England. It was in England that the name King's Cure-all was adopted. Externally, evening primrose was used to heal wounds and calm skin that was inflamed. Internally, the Indians used the root of the plant to calm whooping cough, asthmatic cough and tuberculosis cough. In addition, it was used as an astringent, a pain killer, sedative and diuretic."
Baltimore garden writer Tina James popularized this plant and is said to host Evening Primrose Parties at which guests watch the flowers slowly open. The flowers' scent is sweet and attracts butterflies.
There isn't much on the Internet about Tina James. But here's a quote I found, "Gardening is any way that humans and nature come together with the intent of creating beauty."
Her book "Cooking With Herbs: 100 Seasonal Recipes and Herbal Mixtures to Spice Up Any Meal" was published by Rodale Press in 1999.
At any rate, I probably shouldn't have planted it where I did but I couldn't resist the idea of having it close by and watching the flowers open.