Virginia Buttonweed (Diodia virginiana) 2015-7-25 Newark, DE - Found growing in a ditch and spreading in grass. This is not Long-leaved Bluet (Houstonia), as originally thought.

D. virginiana: https://gobotany.newenglandwild.org/species/diodia/virginiana/
Rough Buttonweed (D. teres) is similar but grows more upright, is much hairier, has a much shorter funnel than D. virginiana
http://www.ncwildflower.org/plant_galleries/details/diodia-teres