Evening Primrose is a biennial, producing a rosette the first year, and a flowering stalk the second. It will grow in full sun and shade, though prefers the sun. Unlike many other edible plants listed here, evening primrose prefers dry soil. Host to fifteen species of caterpillars, evening primrose also plays a unique role in the ecosystem as the flowers open in the evening and close in the morning. Aside from many moths, bats also love evening access to the flowers.
A highly-edible plant, the roots can be eaten raw or cooked, the stems edible (though preferably when young), the leaves are good before the flowers appear, the flowers themselves are edible, and the seeds are, not surprisingly, edible and nutritious. There are about 145 species of Oenothera, all native to the Americas. Oenothera biennis is the common evening primrose, and apparently the most well-known based on my own research. Thus there may be a large untapped resource for harvesting, but is largely unknown. I have found references to edible parts of O. elata, O. lamarckiana, O. californica, O. nutalli, O. brevipes, O. fruticosa, O. pallida, O. villosa, and O. speciosa.
Map Source:
USDA Plants Profile