Asters are adaptable, daisylike flowers with peak bloom season in fall. New England aster, pictured here, is available in colors ranging from lavender to pink, white, purple, and rose. It is a great middle-of-the-border plant, growing 2-5 feet tall.
Name: Aster novae-angliae selections
'Crown of Rays' goldenrod has spiky yellow blooms in late summer on a tidy plant that stays under 2 feet tall. It is well-behaved, spreading gradually to form a large clump in the border, Other goldenrods are also clay-resistant, but can grow up to 5 feet tall.
Name: Solidago 'Crown of Rays'
Russian sage grows so well in hot, dry, sunny clay that in some areas it is considered invasive. (So check local restrictions before planting it.) Its wispy lavender flower spikes and silvery foliage make it an anchor of the summer border.
Name: Perovskia selections
Tough-as-nails daylily grows almost anywhere. Its trumpet-shape blooms each last only a day, but plants can bloom for several weeks because they produce many flower buds. Some varieties bloom several times through the summer. 'Country Melody', shown here, has a peachy pink bloom with a creamy yellow throat.
Name: Hemerocallis selections
Watch this quick video and learn more about growing beautiful, adaptable daylilies.
Yarrow is a tough plant that grows well in dry, sunny conditions. Fern-leaf yarrow, pictured here, has silvery-gray foliage with clusters of golden-yellow blooms that are attractive to butterflies. It's also deer-resistant.
Name: Achillea selections
Little bluestem is a gorgeous grass from the North American prairies that bears blue-green foliage that turns crimson in fall. 'Blue Heaven', seen here, has especially blue leaves. It sends its roots deep into the soil and withstands long periods of drought.
Name: Schizachyrium scoparium
Fountaingrass offers bottlebrushlike seed heads that gracefully arch outward from a mounded plant. 'Hameln', pictured here, is a dwarf variety that grows about 2-1/2 feet tall and wide. It makes a great low-maintenance ornamental grass.
Name: Pennisetum selections
Among the most versatile of ornamental grasses, switchgrass thrives in moist, dry, or clay soil -- and even in part shade. It offers wispy seedheads that sway gracefully in the breeze. Some varieties, such as 'Heavy Metal' have bluish-green foliage; others turn shades of red and maroon in autumn.
Name: Panicum selections
With a name like ironweed, you know that this perennial flower is tough. It thrives in clay, tolerates summer heat, and withstands long periods of drought. In late summer it bears purple flowers that attract butterflies.
Name: Vernonia selelctions
Tropical-looking canna offers dramatic foliage and bright blooms. Look for a wide range of varieties -- some grow only 2 feet tall; others tower over 6 feet. It grows well in poorly drained soils and even tolerates standing water.
Name: Canna selections
Test Garden Tip: In colder Zones, dig and store canna rhizomes over winter in a frost-free place.
Bluestar is a garden champ because it adapts to most growing conditions, from soggy sites to dry clay, and full sun to part shade. It shines in midspring with steel-blue, star-shape flowers and again in fall, when the lustrous willowy foliage turns bright gold.
Name: Amsonia selections
Also called false indigo for its blue springtime flowers, baptisia is a native prairie plant with deep roots that push through the toughest clay soil. Other selections extend baptisia's color range to white, yellow, and purple.
Name: Baptisia selections
Coreopsis is a long-blooming summer perennial flower. 'Zagreb' threadleaf coreaopsis, shown here, has fine feathery foliage, and spreads to make an effective sun-loving groundcover in heavy clay soil.
Name: Coreopsis selections
Purple coneflower is a butterfly-and-bird magnet for sunny sites. Though it loves well-drained soil, it tolerates clay. 'Ruby Star', pictured here, is one of many varieties available. Also look for hybrids with colors ranging from pink to white, orange, burgundy, and red.
Name: Echinacea selections
Sea holly is a wonderful plant for adding texture to the garden. It offers jagged leaves with clusters of steel-blue flowers surrounded by a crown of spiny-looking bracts. Related to thistles (though it doesn't spread like them), sea holly is also deer- and rabbit-resistant.
Name: Eryngium selections
Test Garden Tip: Rattlesnake master and Miss Willmott's ghost are two other types of Eryngium that grow well in clay.
Also called cranesbill for the shape of its seedpods, perennial geranium makes a great groundcover on sites with clay soil. It grows in full sun to part shade, and blooms profusely in spring. Some varieties continue to bloom throughout the summer. Many develop wonderful fall color to boot.
Name: Geranium selections
It's hard to beat false sunflower for garden performance. This tough perennial blooms all summer long and boasts impressive heat- and drought-tolerance. Most varieties, such as 'Summer Sun', shown here, grow 3-5 feet tall. 'Tuscan Sun' remains under 3 feet tall, perfect for small-space gardens.
Name: Heliopsis selections
'Paris' coral bells produces a frothy sea of pink blooms floating above silvery green foliage, so even when this perennial flower is not in bloom, it looks great. Other varieties are grown strictly for their attractive foliage colors, with shades ranging from deep purple to bronze, peach, silver, and mixtures of the above.
Name: Heuchera selections
A favorite in the shade garden for its attractive foliage, many hostas also produce pretty spikes of white or lavender blooms. 'Patriot' hosta, pictured, has blue-green leaves dramatically edged in pure white.
Name: Hosta selections
Blazing star is a native prairie plant that has become a popular cut flower and a must-have perennial for butterfly gardens. It offers spikes of purple or white flowers over clumps of grassy foliage.
Name: Liatris selections
Bee balm is an old-fashioned favorite that produces flowers in shades of red to pink, lavender, and purple. It grows in heavy soil, attracts hummingbirds, and is deer- and rabbit-resistant.
Name: Monarda selections
'Autumn Joy' sedum is a drought-resistant perennial flower that grows well in most soil types, even dense clay. Plant it in full sun for best results. Its late-summer blooms attract butterflies.
Name: Sedum 'Autumn Joy'
Also called Adam's needle for its sharp, pointed leaves, yucca shines in the early summer garden when it sends up a towering candle of waxy white blooms. Perfectly at home in desert climates, Adam's needle yucca also grows well in clay soil in more humid regions.
Name: Yucca filamentosa
Miscanthus bears silvery seed heads that seem to glow in the late-summer and autumn sunshine. This ornamental grass grows nearly anywhere, from soggy soil to sun-baked clay. It can drop a lot of seedlings, so deadhead the plumes as they mature to keep it from becoming weedy in your garden.
Name: Miscanthus selections