Asiatic and LA hybrid lilies, and dianthus bloom for me in that time and don't forget the hardy roses. Mordens and minis don't take up much space and are ever bloomers. 'Madame Julia Corravon' is an everblooming clemmie and the hardy honeysuckles are good for vines. Gaillardia 'Goblin' is one of my favs at this time and the salvias are usually still performing. Lychnis coranaria 'Rose Campion' too (although that lychnis might be invasive in some of your areas). Delphs and daisys are a must have for me.
