Ornamental Oat Grasses

Sapphire is a cultivar of blue oat grass with green and white leaves.

Ornamental oat grass varieties are but one of the many grasses now being used in landscapes, from edging ponds to specimen plants in a container. Ornamental grasses have a home in the informal garden as well as in the formal. They provide a shift away from a focus on the bright colors of flowers and shrubs to an emphasis on subtle shades, textures and movement. Increase the visual pleasure of the garden by adding a new dimension with ornamental oat grasses.

Types

Site ornamental grass where the setting sun provides a backlight to its texture.

Ornamental oat grass is available in two distinct types. The blue oat grasses (Helictotrichon sempervirens) remain evergreen year round with narrow foliage in a steel blue shade. It has the shape of a porcupine, rounded with spiked leaves reaching up to 2 feet and spilling over. Northern sea oats or wild oats (Chasmanthium latifolium) are an upright bright green (or green and white depending on the variety) oat grass with broad bamboo-like leaves. Its foliage stretches to 3 feet and offers fiery yellow and brown color as it begins fall dormancy.

Method of Growth

Ornamental grasses spread by underground stems and many can be invasive. These rhizomes sometimes increase by running in all directions, expanding the area covered by the grass quickly. These are referred to as running grasses. Oat grasses are a clumping type, which slowly increase the width of their clumps. They are easier to contain to one specific site than a running variety of ornamental grass.

Climate and Light Requirements

Northern sea oats thrive in USDA zones 5 through 8 and can be grown successfully in full sun to full shade. Blue oat grass does well in zones 4 through 9 and needs a site in full sun or only light shade. Shade makes the blue oat grass weak with sparse growth.

Water and Food

Oat grasses are especially good for organic gardens because they seldom need fertilizers or regular watering. They require watering only in the hottest and driest months of summer. Both types of oat grass enjoy a fertile, well-drained soil rather than either a hard clay or an extremely sandy soil content.

Benefits

Flowers from the ornamental oat grasses are useful to cut and dry for winter bouquets. Chasmanthium latifolium blooms from mid-summer to early fall on arching stems 3 feet above the foliage, leaving dangling flat, golden seed clusters in the fall. The Helictotrichon sempervirens sends up 1-foot spikes in early to mid-summer with white to beige flowers on top.

Fall Care

Fall care for Chasmanthium latifolium, northern sea oats, requires cutting off the deciduous foliage as it dies back. The Helictotrichon sempervirens, the tufted blue oat grasses, should not be cut back. Pull any withered leaves from these as they appear, by hand or by gently pulling a steel rake through the leaves to remove the dead ones.

References

• "The Encyclopedia of Ornamental Grasses"; John Greenlee; 1992
• "Taylor's Guide to Ornamental Grasses"; Roger Holmes; 1997
• Skagit Gardens: Chasmanithium-River Mist

Resources

• University of Wisconsin: Blue Oat Grass