The Best Plants for Septic Mounds

Wildflowers

• Wildflowers offer the benefits of natural resistance to pests and diseases. The University of Minnesota includes pussy toes (Antennaria solitaria) and ox-eye (Heliopsis helianthoides) on its list of the best wildflowers for septic system plantings. Pussy toes grow less than 6 inches tall and bloom in spring with clusters of fuzzy white-gray flowers. This perennial thrives in partial to full shade and well-drained soil. It tolerates dry soil and can be grown as a ground cover. The ox-eye grows from 2 to 5 feet tall and blooms from summer through fall with 3-inch-long, multi-petaled yellow flowers. This perennial has pairs of pointed leaves and smooth stems. Its natural habitat ranges from woodlands to meadows, so plant ox-eye in light to dappled shade and well-drained, moist soil.

Perennials

• Perennials bloom year after year, often dying back during cool months and reviving in spring. The Virginia Cooperative Extension lists delphiniums (Delphinium spp.) and daylilies (Hemerocalis spp.) among the best perennials for septic system planting. Delphiniums grow to 5 feet tall and bloom with spikes of blue, white and purple flowers in summer. They are hardy in U.S. Department of Agriculture plant hardiness zones 2 to 7 and grow well in full sun and well-drained, alkaline soil. Daylilies bloom in spring and summer with pink, maroon, orange or yellow flowers. They prefer rich, well-drained soil and tolerate full sun to partial shade. Daylilies are hardy in USDA hardiness zones 3 to 9 and grow from 2 to 3 feet tall.

Ornamental Grasses

• Grasses provide cover all year, and their shallow but extensive root systems help prevent erosion. Some of the best species for septic system planting sites, according to the University of Minnesota Extension, include little blustem (Schizachyrium scoparium), a sun-loving grass that grows to 4 feet tall. This upright species has blue to green foliage that turns red, orange or bronze in fall. It produces silvery inflorescences, tolerates a variety of soils and is hardy in USDA hardiness zones 4 to 10. Prairie droopseed (Sporobolus heterolepisis) grows to 15 inches tall and is hardy in USDA hardiness zones 4 to 8. This arching grass grows in a mound of fine, lustrous green foliage that turns orange to copper in autumn. It produces fragrant panicles in late summer. Prairie droopseed prefers sun to light shade and tolerates drought.

Ground Covers

• Ground covers fill in empty sites on the septic field and generally require little maintenance. The Washington Sea Grant Program recommends kinnickinick or bearberry (Arcrostaphy los uva-uisi) and chameleon plants among the best ground covers. Kinnickinick, an evergreen, is hardy in USDA hardiness zones 3 to 7 and grows from 1 to 4 inches tall. This slow-growing plant creates a low, dense carpet of leathery and dark foliage. It blooms with white-to-pink spring flowers and produces red berries in fall. It prefers sun to light shade and well-drained, acidic soil. The chameleon plant is hardy in USDA hardiness zones 5 to 8 and grows from 12 to 15 inches tall. It thrives in sun to light shade and a range of moist soils. Chameleon plants have aromatic, deciduous, heart-shaped foliage and bloom with white bracts of yellow flowers.