Roof Garden Ornamental Grasses

Tall Grasses

• Tall grasses, often featuring striking tufts or seed heads during the late summer and fall, add visual interest while retaining the benefits of low-maintenance grass. Many other plants that grow to heights of 1 to 4 feet require deep roots for support that outgrow a shallow layer of dirt common in roof gardens, or they can't withstand the harsh sun and wind. Northern sea oats and blue oat grass are two good choices in this grass category.

Short Grasses

• A patch of shorter ornamental grass varieties is a good choice for the center of a roof garden, especially if you plan to use the garden as a patio as well. Prairie grasses do well on roof gardens or green roofs due to their acclimation to harsh conditions and shallow root structure. Blue grama is a good choice. Its maximum height is between 6 and 12 inches, except for the 18-inch flower stems capped with a crescent moon-shaped cluster that are present during the end of summer.

Bunching Grasses

• Ornamental grasses that grow in natural clumps or bunches adapt well to life in a container of limited size. They range in height from 6 inches to 6 feet, and many feature taller flower stems surrounded by a cluster of short grass blades. Prairie dropseed has decorative seed heads in the fall and is visible even under heavy snow. As a perennial it will self-seed and fill a container naturally after a few years of growth.

Brightly Colored Grasses

• Most plants featuring large, showy flowers are too delicate for the harsh conditions of a rooftop garden or green roof. To add color to your roof, try brightly colored ornamental grasses, suggests the University of Missouri Extension Service. Blue fescue is a clumping grass that has foliage of a silver blue. Sun increases its blue tones, and most roofs receive direct sun all day long. A variety of bright red grasses that can handle rooftop conditions are also available, including Japanese blood grass.