There is no one best grass to cover all types of embankments. Cover grasses vary greatly according to their kind and attractiveness and if they are useful for embankments which are dry or the ones which are frequently wet. Bunch grasses spread by seed while those who form sod spread by underground stems called rhizomes or above-ground stems called stolons. In moist places, seeds are often difficult to plant on an embankment because they get washed off.
Grass for Moist Embankments
The sod grass Meadow foxtail (Alopecurus pratensis) grows well in low pH soils which drain poorly. University of Nevada-Reno horticulturalists urge A. pratensis “Garrison” for planting on embankments facing streams. Meadow foxtail grows as a perennial in warm climates. Mountain brome (Bromus marginatus) is best planted in grass combinations to control erosion. It grows 1 to 4 feet high across the west and from Canada to Mexico on the Pacific Coast. The attractive hairgrass (Deschampsia caespitosa) rises in bunches which are leafy at the bottom. Typically located in mountain meadows and along stream banks, it is beneficial for controlling erosion on embankments. It rises in U.S. Department of Agriculture plant hardiness zones 4 through 9.
Bunch Grass for Dry Embankments
The slow-growing hard fescue (Festuca trachphylla) ought to be planted with slender wheatgrass or a different grass that establishes rapidly. It rises from 1 to 2 feet high and contains dense, fibrous roots which make it good for controlling erosion on deep, coarse textured soils. F. trachylla “Durar” will grow in a vast array of soils in climates which have 12 or more inches of rain a year. Probescent wheatgrass (Agropyron trichophorum) is much like intermediate wheatgrass but establishes more gradually. It grows 2 to 4 feet high in a wide range of temperatures and rainfall and is good for covering embankments with inadequate soil.
Sod Grass for Dry Embankments
The green to blue-green intermediate wheatgrass (Elytrigia intermedia) produces ample roots and rises from 2 to 4 feet high. A dwarf cultivar, E. intermedia “Tegmar” is much more drought-tolerant than other varieties and quickly produces a sod of deep, fibrous roots. It will grow in temperate climates using a rainfall of at least 15 inches a year and is especially good for steep exposed embankments which get lots of sunlight. Sheep fescue (Festuca ovina) rises 1 foot high and is extremely effective at controlling erosion. F. ovina “Covar” is a drought-tolerant cover for dry embankments that face south and west. It rises in USDA plant hardiness zones 4 through 9.
Smooth brome (Bromus inermis), a sod grass, which grows from 1-1/4 to 4 ft high and is useful for controlling erosion on moist dirt. The deep-green B. inermis “Manchar” has broad brown seedheads that include color and contrast to grass mixes. Smooth brome grows on the West Coast from Canada to Southern California. Indian ricegrass (Oryzopsis hymenoides), an attractive native of the Great Basin, rises 1 to 2-1/2 feet high and is also good for erosion control on dry, sunny sites in USDA plant hardiness zones 3 through 9. Horticulturalists in the UN-Reno urge the “Nezpar” and “Paloma” cultivars which have dramatic, wide-spreading seedheads. The attractive blue-green bunch grass blue wild rye (Elymus glaucus) rises in loose bunches 2 to 4 feet high. It grows well on embankments and is spread down the Pacific Coast.