Answer: There are many purple perennials that you can use. You can select them so you can have blooms from spring through fall. I highly recommend that you look through some perennial books in the library or bookstore to help you become familiar with flower forms and cultural needs.
Here's a list to get you started, but this is just a small fraction of what's out there: Aster 'Purple Dome', butterfly bush (Buddleia davidii 'Nanho Purple'), delphinium, Delosperma, 'Johnson's Blue' Geranium, iris, Liatris, lavender, Perovskia, Nepeta 'Dropmore', Scabiosa 'Butterfly Blue', salvia (many purple shades), Verbena 'Homestead Purple', Gladiolus 'Blue Heaven'.
Annuals: Lisianthus 'Balboa Blue Rim' and 'Blue Rose', blue-eyed daisy, 'Lavender Wave' petunia, Heliotrope, annual verbena, Laurentia, pansy, Scaevola, Plumbago 'Powder Blue'.
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