Kentucky bluegrass, bermudagrass and zoysiagrass produce more thatch than other grasses such as perennial ryegrass and tall fescue. Kentucky bluegrass, for example, has rhizomes, simply described as underground stems which spread or fill in areas. Bermudagrass and zoysiagrass have both rhizomes and stolons, or "above ground" stems. Although these rhizomes and stolons help the plant maintain its density and recuperate from injury, they adversely contribute to thatch accumulation. Grasses such as perennial ryegrass and tall fescue do not spread the same way and, therefore, do not produce much thatch. When possible, using a mixture of cool season grasses will help decrease the potential for large thatch accumulations.
Areas of the country where warm season grasses such as zoysiagrass and bermudagrass predominate do not have the luxury of using seed mixtures and need to look for the newer cultivars of these warm season grasses. These newer cultivars have improved grass qualities and produce less thatch than the older common types.