Unfortunately, most perennials do not bloom for a long period, but if one chooses plants with effective foliage and/or texture, they present benefits in addition to blooms.
Heucheras, (The common name is coral bells.), have dainty spires of flowers in pink, white, and coral shades and have a neat mounding habit and are only 12-18 inches tall.
They are known for their neat round or heart-shaped leaves. The foliage has an array of different colors with pretty, ruffled edges, and the leaves come in an array of different colors in the modern varieties.
Newer cultivars are the most striking. For example, ‘Lime Rickey' (zones 4-9) has chartreuse leaves that change to lime by midsummer, and ‘Marmalade' is lovely with sienna-colored leaves that have pinkish-colored undersides (also hardy zones 4-9).
One may choose to select two different contrasting varieties. For example, one with a chartreuse leaf and one with a purple leaf and intersperse them along the edge of a border or just mass them in color blocks in a shade bed.
They need moisture-retentive soil that is well drained, as they won't survive boggy conditions. In northern climates they enjoy some morning sun, but in the south they do better with more shade and filtered light.
Coral bells also thrive in containers.