Perennials for Heavy Clay Soil

Herbaceous and woody perennial plants have fine root systems, which can make gardening in clay soil challenging. Clay can become compacted and waterlogged, suffocating roots easily. However, there are a number of plants well adapted to these conditions that provide summer color and seasonal interest.

Aster x frikarti and Aster novae-angliae bloom in midsummer with a profusion of flowers similar to a daisy. The commonest colors are shades of blue and pink. Asters are a good nectar source for butterflies, and continue blooming all the way into fall. From a distance, the plant appears to be a solid mass of flowers, and makes an impact planted in groups. Hardy to zone 3.

Echinacea, also called purple cone flower, now comes in a variety of colors. 'Tomato Soup' is bright red, and looks great interplanted with 'Summer Sky' and 'Tiki Torch' which have blends of orange and peach coloration. Echinaceas can grow to four feet tall, so in an area with limited space smaller types such as 'Red Knee High' , 'Raspberry Tart' and 'Prairie Splendor' would be more appropriate. The dwarf varieties will stay under two feet, but they do not have the range of color as the full size echinaceas. Hardy to zone 3.

Hemerocallis (Daylily) is often considered to be an overused plant, simply because it is so tough and adaptable. The name 'daylily' refers to the fact that the flowers only last one day, but newer cultivars are rebloomers and some are even fragrant. 'Double Misty Dawn' is not only a rebloomer, it has double flowers and smells wonderful. 'Barbara Mitchell' is another rebloomer with flowers resembling an Amaryllis. There is a very extensive range of color in the daylily family, with the exception of blue. Hardy to zone 4.

Iris ensata, (Japanese Iris) is so tolerant of clay it will even grow in waterlogged conditions and is deer resistant as well. Although it has a comparatively short blooming time, the flowers are so stunning it is worth growing. 'Night Blizzard' is a vivid purple streaked with white, with yellow centers. 'Joyous Troubadour' has white petals delicately lined with blue. Hardy to zone 5.

Rudbeckia (Black Eyed Susan) is yet another daisylike plant, with yellow flowers and dark centers. 'Goldsturm' is the most reliable variety for heavy clay. Stay away from the biennial cultivars, which tend to need better drainage. Hardy to zone 3.