What Type of Grass Seed Is Best for Clay Soil?

Clay soil is not the ideal medium in which to grow turf grass. Clay consists of very fine particles that tend to bind tightly together, creating a heavy, dense, compacted soil. Clay soil usually does not drain well, which is a problem for grasses that do not do well with their roots in water-saturated soil, and grass roots can have a difficult time pushing their way through dense clay as they grow.

The best grass varieties for clay soil are those with deep, strong root systems that can work their way through the heavy soil. Even those varieties, however, fare better when the clay soil is improved before the grass seeds are sown.

Cool-Season Grasses

Cool-season grasses are species adapted to northern climates. They grow best during cool spring and autumn weather, and they are able to survive cold winters in the northern United States. They go dormant during the hottest parts of summer, and they do not fare well in the South.

Among the cool-season grasses, tall fescue (Festuca arundinacea) is one of the best choices for clay soil. It has a substantial root system that helps it deal with dense soil, and its deep roots also help it tolerate heat and drought. Tall fescue is winter-hardy in U.S. Department of Agriculture plant hardiness zones 2 through 7.

Warm-Season Grasses

In contrast to cool-season grasses, warm-season species thrive in hot climates. They grow actively during midsummer heat, and they often go dormant as the weather begins to cool in fall. They are not nearly as cold-tolerant as cool-season species, however, and they are unlikely to survive in the northern United States.

In the South, where red clay soil is common, zoysiagrass (Zoysia spp.) is an option for areas where the soil is clay. Like tall fescue, zoysiagrass has a dense root system that helps it tolerate heavy soil as well as heat and drought. Zoysiagrass is winter-hardy in USDA zones 6 through 9.

Improvement of Clay Soil

Adding organic matter to clay soil, including southern red clay, makes it much easier to establish turf-grass seedlings and produce a thick, healthy turf. Compost or peat moss improve the texture of clay soil, allowing water to drain quickly and creating air spaces that help grass roots breathe and grow. The organic amendments also improve the soil's nutrient content.

To improve heavy clay soil, add 1 to 2 cubic yards of compost or peat moss per 1,000 square feet of the soil, using a tiller to incorporate the amendments into the top 6 to 8 inches of soil.