Clay soil's heavy texture, low oxygen and nutrient levels and tendency toward alkalinity combine to create inhospitable growing conditions for most perennials. Clay soils usually have poor drainage, leading to stickiness, and, when dried, rock hardness. With a bit of effort -- and lots of soil amendments, such as compost -- certain clay-tolerant perennial species can grow in sites with clay. Before planting, determine your site's light exposure and U.S. Department of Agriculture plant hardiness zone, which defines the lowest annual average temperatures in your region.
Plant sun-loving perennial species in sites that receive direct sunlight in the summer between the hours of 10 a.m. and 6 p.m. Clay-tolerant perennials for full sun include woolly yarrow (Achillea tomentosa) and fernleaf yarrow (Achillea filipendulina). These adaptable flowers bloom from late spring through summer with white, gold, pink and red flowers that attract butterflies. Yarrows grow to 3 feet tall and are hardy in zones 3 to 9.
The aster (Aster x frickartii) tolerates clay and prefers full sun. These perennials grow from 1 to 4 feet tall and bloom from summer to fall with long-lasting, yellow-centred lavender flowers. Asters attract butterflies and are hardy in zones 5 to 8.
Sites with light shade receive five to six hours of direct sunlight. The spike gayfeather (Liatris spicata) grows well in light shade and tolerates clay. This low-maintenance perennial blooms with tall spikes of blossoms that bloom from top to bottom and last from summer through fall. Gayfeathers grow to 3 feet tall and are hardy in zones 3 to 9.
The cupplant (Silphium perfoliatum) thrives in light shade. This large perennial can grow from 6 to 9 feet tall with foot-long, cup-shaped foliage that provide shelter for birds. Cupplants bloom with bright yellow flowers.
Sites with partial shade only receive three to four hours of sunlight or experience a dappled shade all day long. Monkshood (Aconitum spp.) grows in partial shade and tolerates clay. Monkshood grows up to 4 feet tall and blooms with blue to purple flowers in midsummer. This perennial has toxic roots and foliage and is hardy in zones 3 to 7.
The columbine (Aquilegia Canadensis) also thrives in partial shade and tolerates clay. These flowers grow from 1 to 2 feet tall and bloom in spring. Columbines have bell-shaped, red and yellow blossoms and are hardy in zones 3 to 8.
Sites in full shade, like those under evergreen trees or overhangs, don't experience any direct sun exposure. Leopard's bane (Doronicum spp.) tolerates sites with full shade and clay soil. Leopard's bane flowers in spring with yellow, daisy-shaped blossoms and grows from 1 to 2 feet tall. Leopard's bane is hardy in zones 4 to 7.
Goldenray (Ligularia stenocephala) also grows in shady, clay sites. This flower grows to 5 feet tall and blooms in summer with tall towers of small, yellow blossoms. Hardy in zones 5 to 7, ligularia doesn't thrive in sites with hot afternoon sun.