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. Geranium. Probably one of the longest flowering garden plants, hardy geraniums start flowering around may, and continue to october, depending on the variety. One of the longest flowering varieties is geranium ‘johnson’s blue’ (illustrated) which is also attractive to bees.