Prairie Sundrops (Oenothera pilosella), also sometimes called meadow evening primrose, midwestern sundrops or common sundrops, is a herbaceous perennial plant in the family Onagraceae evening primroses, that is seen in a wide range of habitats. The common name refers to the Grand Prarie of the Gulf Coastal Plain of Alkansas. Native to the Continental US and Canada, this striking species seems equally at home either in the dry prarie soil along railroads, river terraces or in low swampy woods. It has two 2-foot stems with clusters of bright yellow flowers at the top and little rosettes at the bottom. Mature 4-petal buds are erect opening near sunrise. The plant flowers from May to June. Prairie sundrops is of special Value to native bees and is recognized by pollination ecologists as attracting large numbers of native bees. Prairie sundrops was a popular garden plant in the nineteenth century, although it is less commonly cultivated now. It spreads semi-aggressively and forms dense mats, but can be removed easily from a garden setting because of its shallow roots.