- Blue false indigo (Baptisia) typically grows up to 5 feet tall and wide, and hates to be relocated once established. New varieties, like Baptisia ‘Sparkling Sapphires’, grows only 2 ½ to 3 feet tall and wide. It is hardy in Zones 4-9, and can be combined with other sun-lovers like peonies and Siberian iris.
- Nepeta (sometimes called catmint) Nepeta ‘Purrsian Blue’ is a newer variety that stays under 20 inches tall with a spread of around 30 inches. Because of their fragrant foliage, they are resistant to deer and hardy in Zones 3-8. Combine it with annual or perennial poppies.
- Clematis is available in a huge range of pale to deep purple. ‘Happy Jack’ and ‘Rooguchi’ offer deep plum, while ‘Brother Stefan’ is medium blue and ‘Betty Corning’ is a pale lavender-blue. Most Clematis are hardy in Zones 4-8 and look great as a backdrop to Hydrangeas like ‘Endless Summer’.
- Siberian Iris don’t need to be divided as often as the bearded iris, and have leaves that stay green and provide a vertical accent. They bloom along with peonies and Allium and reach a height between 18 and 36 inches. Combine them with Shasta daisies for a beautiful contrast.
- Poppies (Papaver): If you pick annual seed-grown poppies, they’ll bloom for more than a month. This is especially true with hybrids like ‘Lauren’s Dark Grape’. For paler purple, try ‘Lilac Pompon’, a double type. Combine poppies with a planting of dill for an airy combination.
- Butterfly bush (Buddleja) New varieties of this butterfly magnet are more compact, with bigger blooms. ‘Orchid Annie’ reaches up to three feet with eight inch long orchid purple flowers. Lo and Behold ‘Blue Chip’ reaches just 30 inches. Both look great with coneflowers and ornamental grasses.