I have a friend who just bought an older house in Northern/Central Indiana, and these are coming up all over the garden beds through the weed-protecting fabric. She's not sure if it is a weed or an intentional plant.
Commented on May 05, 2012
It's a primrose. Here in NM, we have them in pink, yellow & white. The white ones, if I'm not
mistaken, are Oenothera caespitosa aka Tufted Evening Primrose or Fragrant Evening Primrose. They look beautiful in drifts. I much prefer the white ones over the yellows & pinks.