What is the longest flowering hardy perennial?
Some of the best include geranium rozanne, famous for its incredibly long flowering season, and salvia caradonna, which blooms early and often. Gaura whirling butterflies, verbena bonariensis, scabiosa butterfly blue and nepeta six hills giant also flower for much of the summer. Some flowers like coneflower (echinacea), shasta daisy (leucanthemum), spike speedwell (veronica), queen-of-the-prairie (filipendula), and yarrow (achillea) started to bloom in june and often continue into the summer months.