Winter cress has an edible flower, but it's a bit too strong for me.  (more)

 

Spring cress is pungent, a bit more edible than winter cress.

Medicinally (folklore) used as a heart tonic.

Sand cress, Arabis lyrata, variety of winter cress, found on Michigan dunes.  Edible flower about 1/4 inch across.  Flower size about half that of winter cress and twice as big as shepherd's purse.  Spicy, pungent.