A single, well-chosen plant can create drama in a pot. For example, take meadow rue. During summer, clouds of blooms cover its delicate stems, making this plant superb for creating an airy effect against a wall or dark green background. Many other perennials are showy enough to grow singly in pots; some are listed below.
To extend the season's show, fill several beautiful stoneware or Italian terra-cotta pots with perennials that peak at different times―late spring, early to midsummer, and midsummer into fall, for instance. You can move them out of sight after they've bloomed. Climate zones are from the Sunset Western Garden Book.
Aster (A. x frikartii 'Wonder of Staffa' and 'Mönch'). Clear lavender to violet blue single flowers on plants to 2 feet tall. Sun; early summer to fall. Zones 2b-24.
English lavender (Lavandula angustifolia 'Munstead', 'Hidcote', or 'Sharon Roberts'). Spikes of fragrant blooms. Sun; late spring. Zones 2-24.
Gaura lindheimeri. Wispy spikes of white flowers. Sun; late spring through summer. Zones 2b-24.
Geum chiloense 'Mrs. Bradshaw'. Double scarlet blooms atop 2-foot stems. Part shade in hottest climates; late spring. Zones 2-24.
Meadow rue (Thalictrum). Clouds of small lavender blooms appear in late spring. Light shade. Zones 2-10, 14-17.
Santa Barbara daisy (Erigeron karvinskianus). Trailing plant 10 to 20 inches tall and 3 feet wide with dainty, daisylike flowers in white and pink. Plant in a low, wide bowl. Sun to light shade; rarely out of bloom. Zones 8-9, 12-24, H1-H2.
Stokes aster (Stokesia laevis). Large (3- to 4-inch) asterlike blooms of blue, purplish blue, or white on plants to 2 feet tall. Sun; summer or early fall. Zones 2-10, 12-24. Evergreen in warmer climates.