Pink Ladies, Showy Evening Primrose

(Oenothera speciosa) 9/2/11 D&M MD - Often cultivated in gardens outside its wild range.
http://plants.usda.gov/java/profile?symbol=OESP2&photoID=oesp2_007_avp.jpg

http://www.illinoiswildflowers.info/prairie/plantx/sh_primrosex.htm