We are approaching a transitional period in the perennial garden. Late spring color is bursting forth, with terrific plants such as Siberian Iris and Peonies. It seems now that color abounds in gardens and the nursery, but in early to late June, there is a bit of a lull until the late-season perennials begin to come into color.
Perennials are either spring-blooming or summer/fall blooming, but seldom both. Okay, I know there are reblooming German Iris, and some cool-evening-loving plants like Dianthus might come back into bloom. Still, as a rule of thumb, you have spring perennials with short blooming periods and summer bloomers with long blooming cycles.