Clay soil is often very alkaline with a pH of 7 to 8.5. It drains poorly and compacts after a rain. All clay soils will have to be amended to improve the drainage and texture, but a beautiful garden is possible if gardeners choose clay-tolerant plants and then plant them properly. Given better than average conditions, plants that will tolerate clay will positively shine.
Trees are often the centre of landscaping designs because of their size. Many species do very well in clay soils, provided they have been properly planted. According to the University of Minnesota Extension, some trees that do particularly well in clay soils are silver maple, shagbark hickory, the entire malus species—apples, crabapples—aspens and cottonwood trees.
Many fruit bearing and flowering shrubs do well in clay soil and are hardy to USDA Hardiness Zones 2 and 3. The lilac grows well in heavy clay soils, as well as currant bushes, forsythias, and deciduous and evergreen viburnum.
Perennials are not typically easy to grow in clay soil. All of them require a slight elevation of the planting hole along with an amendment of organic compost. Many of these perennials, such as black-eyed Susans, Russian sage, potentilla and columbine, are also drought tolerant, while some, like coneflower, require good drainage. Plant aster, Joe-Pye weed, heliopsis, hostas, daylilies, geraniums, foxglove, loblia, phlox, ferns and switchgrass.