Clay soil is heavy soil that has little sand content. It holds water well--often too well. When dry, clay soil is extremely hard and not easily cultivated. The soil itself feels smooth or slick. Because clay soil is so dense, roots have a difficult time spreading, which can stunt plants. Choosing plants that grow well in clay soil will ensure a successful garden.
Most drought-tolerant annuals can handle clay soil. Some of the easiest to grow include poppies, cosmos, zinnias, moss rose, nasturtium, celosia and cleome.
Daylilies are tough enough to handle almost any soil, even clay. They are fairly shallow-rooted and don't require a lot of water. Juniper is an evergreen ground cover that is very easy to grow. Butterfly weed is a large perennial that doesn't mind wet soil.
Other perennials with shallow root systems that grow well in clay include hostas, Siberian iris, bee balm, aster, hellebore, liatris, echinacea, salvia and Russian sage.
Shrubs that are well suited for clay soil include azalea, honeysuckle, snowberry, forsythia, chokeberry, lilac, spiraea, lady's mantle, goat's beard and sea oats.
Trees that can tolerate clay soil include silver maple, European alder, crabapple, white pine, linden, Eastern pin oak and Norway spruce.
Amending Your Soil
Digging up your clay soil and amending it can vastly improve its properties. Incorporate decomposed leaves and pine bark, cow or mushroom manure, or compost at least 4 inches down. Peat moss, pine straw and sawdust should not be used; they will make the soil more compact.
Never dig, walk on or till clay soil when is it wet. It will form hard balls that are virtually impenetrable to plant roots.