Dame's Rocket (Hesperis matronalis) blooms late spring into very early summer with flower colors including white, lavender, pink, deep purple and rose. Flowers have 4 petals and can produce showy raceme. This plant was blooming in Battelle Darby Creek Metro Park in late May.
Although I've seen quite a bit of it in the park, I've also seen it growing in ditches and alongside woods all around Columbus.
Dame's Rocket seeds are sometimes included in "wild flower" mixes. However, as pretty as it is, it is actually considered an invasive species in Ohio. Cleveland Metro Parks have been working to eliminate it; read more at http://www.clevelandmetroparks.com/Main/Invasive-Plant-Management.aspx