The soft gray leaves of Russian Sage make a beautiful statement against pastels and purples of every hue. The brilliant blue flowers seem to sneak up on you, starting as a faint tint, moving through brilliance and fading back to a soft blue. By the time they’ve fully faded, the season is over and you’ve had months to enjoy your Russian Sage. USDA Zones 5 - 9.
12. Siberian Iris (Iris sibirica)
One of the most attractive and adaptable of the irises. Siberian Iris have the typical iris leaf blades, but unlike many of their cousins, Siberian Iris leaves don't flop or scorch after blooming. The plants remain a contrasting form in the garden long after the blooms have faded. They can spread quickly in moist conditions and require division when they get crowded. In warmer zones they may re-bloom in the fall. USDA Zones4 - 9.
Brunnera has delicate sprays of blue flowers in the spring, even before its leaves fill out. Newere varieties have wonderful variegated foliage. ‘Jack Frost’ is partiularly attractive and widely available. Brunnera eventually self-deadheads, but you can trim it back along with some of the earlier leaves, as summer heats up. New leaves will fill in even fuller. USDA Zones 3 - 9.
Tall Sedum are easily one of the most self-sufficient plants for any garden. If they could defend themselves against deer, they’d be perfect. Sedum are late bloomers, but while they’re waiting for their moment, they have thick glossy leaves and fill out in nice, chubby clumps. The flowers start out green, like a head of broccoli, and eventually finish off in shades of mauve. USDA Zones3 - 10.