If you don't have violets in your garden you definitely should!  Violets are great for filling in spaces to make "green" or "living" mulch in place of wood mulch.  They last from early spring to late fall proving nectar and color.  Violets are a host plant for several butterfly species.  They will spread to fill in empty spaces but they aren't aggressive.  Also, they are mowable and can be added to your lawn to create more plant diversity.  What's not to love?