Keep rockery in bloom year-round

Q: We have a rockery that needs help. We're going to pull out the kinnikinnick that has turned black. We want to add plants that will provide color all season — and we like heaths, heather, and ornamental grasses.

A: The key to successful planting here is to look for plants that like the cultural conditions that a rockery provides: good drainage and sunny exposure. If you want bloom throughout the seasons, choose many different types of plants, so that they will take turns providing flowers.

First, for spring bloom, look at classic rockery plants found blooming in neighborhoods throughout the Northwest. Evergreen candytuft, Iberis sempervirens, has been sporting its white flowers for weeks in warmer parts of Seattle. Soon it will be joined by a succession of bloom. Basket-of-gold, Aurinia saxatilis, has yellow flowers; wall rockcress, Arabis caucasica, blooms with white flowers; common aubrieta, Aubrieta deltoidea, is found in shades from rose to red to purple; and moss pink. Phlox subulata, has blooms of white, pink or lavender blue.

In the fall, plant spring-flowering bulbs such as species tulips, crocus, or smaller narcissus, and you will have a glorious spring.

Sunroses, Helianthemum, will pick up the bloom in late spring and early summer. With gray-green leaves, they reach a height of eight inches and a spread to three feet. Cultivars sound delicious, with names like 'Double Peach' and 'Raspberry Ripple.' Let them tumble down the bank and swarm over rocks. Catmint, Nepeta x faassenii, blooms at the same time with lavender-blue flowers and grows to one foot tall.

The stonecrops, of the genus Sedum, are wonderful rockery plants, providing good leaf texture and color. Sedum 'Vera Jameson' has pinkish purple leaves and grows to one foot. The rose flowers provide late summer color. Sedum 'Matrona' is taller and dramatic with its pink flowers on red stems. Sedum telephium 'Autumn Joy' is now a standard, growing two feet tall and two feet wide. The flowers last into the fall, aging from pink to rust.

Scotch heather, Calluna vulgaris, starts blooming in summer and some varieties bloom into the fall. They come in a wide range of colors, and many have bronzy or gold leaf color too.

Heaths, of the genus Erica, are close relatives of heather and are winter or early spring bloomers. Both heath and heather make good rockery plants because they require sun and good drainage. Adding peat moss to the soil will provide the organic, acidic soil conditions that they prefer. Plant them in groups, or sweeps. If you choose heath and heather varieties with care, you can have year-round color.

Grasses can provide interest all year too. One of my favorites for a bank is variegated Japanese sedge, Carex morrowii 'Variegata.' It reminds me of the topknot of a sheepdog, and its cheerful green and white leaves look good all year. Look for a yellow and green cultivar too. These will take a little more water than many of the other rockery plants, so place them where you can give them extra attention. The bronze leaves of leather leaf sedge, Carex buchanani bring great color in the winter too.

Add some long blooming perennials suited to your conditions. Rock soapwort, Saponaria ocymoides is a trailer, growing one foot high and three feet across. The small pink flowers come in spring. Coreopsis verticillata 'Moonbeam' blooms happily from summer through autumn in pale yellow.

Mexican evening primrose, Oenothera speciosa, is white to pink and long-blooming too. An oregano, Origanum laevigatum 'Herrenhausen' will add lilac pink flowers to the summer and fall mix.

Lavender will be happy in the situation, as well as prostrate rosemary, Rosmarinus officinalis 'Prostratus'. The rosemary cultivar 'Severn Sea' is said to be a hardier trailing one.

By choosing among this list of plants, you should be able to put together a colorful composition.