The best way to keep a flower garden colorful from spring through fall, is to include a combination of annuals, perennials and bulbs. That said, perennials are the backbone of most flower gardens, because they rebloom year after year.
Each type of perennial has its own specific flowering period. Peonies and bearded iris, for example, flower for two to three weeks in early summer, then they don't bloom again until next year at the same time. Astilbes put on an amazing display of color in midsummer, but they don't flower during the first and last part of the growing season.
When gardening with perennials, the key is to make sure your flower garden includes plants that bloom during each of the different flowering periods, from late spring through early fall. Please use these lists as a general guide. Bloom times vary depending on where you live and the growing conditions in your garden.
PERENNIALS FOR EARLY TO MID-SPRING
PERENNIALS FOR EARLY SUMMER
PERENNIALS FOR MIDSUMMER
PERENNIALS FOR LATE SUMMER AND EARLY FALL