Clay soil can be notoriously hard on garden plants with its lack of nutrients and hard drying stages. Perennials for clay soil are hardy plants that can live in these conditions. Most clay soil plants are from the aster/daisy family of plants as the hardiest, but there are some from acanthus, mallow, and other families not listed.
The lanceleaf tickseed or lanceleaf coreopsis, botanically known as Coreopsis lanceolata, is from the aster/daisy family. It is an easy to grow perennial good for attracting butterflies. Leaves are 6 inches long and linear with flowerheads 1.5 to 2.5 inches wide on 2 foot stems. Flowers are yellow. Lanceleaf tickseed does well in nutrient poor soil with full sun or partial shade and regular watering. Propagate via spring seed, root division, or by basal softwood cuttings.
The bear's breech or Grecian pattern plant, botanically known as Acanthus mollis, is from the acanthus family. It is a perennial good for containers and shady spots. It can get 5 feet tall in a clump growth. Leaves are dark green and up to 3 feet long. Flowers are white, pink, or purple and very tall over the leaves. It is very soil tolerant and can be grown in full sun or partial shade. Propagate via root cuttings or seed.
The common yarrow or milfoil, botanically known as Achillea millefolium, is from the aster/daisy family. It is a perennial that attracts butterflies to its daisy like blooms and fragrant foliage. Leaves are grayish green and look like fern fronds. Flowers are whitish and 2 to 3 inches wide on stalks 1 to 3 feet tall. Yarrow grows in any soil, even thrives in poor soil, and takes full sun. Propagate common yarrow by spring or fall division or by seed.
The whorled coreopsis or thread-leaved tickseed, botanically known as Coreopsis verticillata, is from the aster/daisy family. It is an easy to grow drought tolerant perennial that attracts butterflies. The plant gets 3 feet tall and 2 feet wide with 2 inch wide flowers in yellow. Leaves are threadlike and lacy. Whorled coreopsis grows in full sun and needs root division every 3 years. Propagate by that division or by seed.
The Shasta daisy, botanically known as Leucanthemum x superbum, is from the aster/daisy family. It is a perennial. The plant gets 2 to 3 feet tall and 18 inches wide. Flowers are white and 2 to 5 inches wide. Leaves are dark green and 8 to 12 inches long, strap like. Grow a Shasta daisy in well drained soil in full sun. Propagate via winter or spring division or by seed.
The hollyhock, botanically known as Alcea rosea, is from the mallow family. It is a perennial grown as an annual and it attracts butterflies. Leaves are rough and 1 to 2 inches long with stems 5 to 6 feet tall. Flowers are funnel shaped and white, yellow, pink, red or purple and 2 to 4 inches wide. Hollyhocks are grown in full sun in well drained soils. Propagate via summer seed.