It is certainly an Oenothera but I can't tell you which species as I am only familiar with O biennis.

Only because I looked through a catalog recently and recognized the leaf, but the yellow is Oxalis Bermuda-Buttercup? Here is a link that might be useful: Propagating Perennials

chervil2, Thanks for reminding me that I needed to mention that if you double click on the photo above it will take you to my on line photo album with many more photos to identify. Once you open the photo album if you click on the largest box in the right hand corner of the page the thumb nail photos will be displayed at a reasonable size or you might prefer to choose view by slide show on the top of the left hand side. Hope that's not too confusing. kt

The folks on the "Name That Plant" forum helped me identify all of them very quickly. For reference, they are: Crimson Clover (Trifolium incarnatum) - first 2 pics Blue-Eyed Grass (Sisyrinchium sp.) - 3rd Nuttallanthus sp. (probably texanus) - 4th Verbena sp. (probably V. canadensis) - 5th