Ornamental Grasses

Prepared by Karen Russ, HGIC Horticulture Specialist & Bob Polomski Extension Consumer Horticulturist, Clemson University. (Revised 11/04. Images added 10/14.)

HGIC 1178

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Ornamental grasses are valued in home landscapes for their hardiness and easy care, dramatic appearance and the wide variety of colors, textures and sizes available.

Pampas Grass, one of the toughest grasses for the South
Pampas grass, one of the toughest grasses for the South.
Karen Russ, ©2007 HGIC, Clemson Extension

Types of Grasses

Ornamental grasses refers to both true grasses and plants that have a grass-like appearance - such as sedges - that are used for similar purposes in gardens.

Most ornamental grasses are perennials, living for two or more years. Annual grasses live for only one growing season, either because of their natural growth or because they are not hardy in our climate.

Grasses can be classed as clumping or spreading. Spreading grasses expand rapidly by aboveground or underground stems. Care must be used in siting spreading grasses, or they may become invasive. Clumping or bunch grasses grow in a clump that gradually increases in diameter.

Ornamental grasses, like lawn grasses, are also classed as cool or warm-season. Cool season grasses begin new growth in fall or winter and bloom in spring or early summer, but go dormant or decline in appearance during the summer heat. Most ornamental grasses for the South are warm season growers. They grow rapidly during spring and summer, bloom in late summer or fall and are dormant through the winter.

Height

Ornamental grasses vary in height from giant reed and pampas grasses reaching up to 15 feet tall, to very low growing grasses used as ground covers. Grass forms vary from low mounds to fountains and tall verticals.

Ornamental Features

The flower heads of many grasses are very showy. Flowers vary in size, color and texture from the airy clusters of tiny purple flowers that float above purple muhly grass to the huge feather dusters of pampas grass. Flowers and seed heads last for weeks or months, many providing interest through the winter.

Foliage provides additional interest with a range of fine to coarse texture, softly arching or firmly upright form and deep green, blue, red or purple, yellow and variegated leaf color. Many grasses have good fall color, changing to yellow, orange, red or purple before fading to tan or straw for winter. Some cool season grasses are evergreen.

Grasses also give interest to the garden in ways that few other plants can. They sway easily in the wind, adding the appeal of movement and rustling sound to the landscape. Their rapid growth and changing appearance through the year adds seasonal interest.

Landscape Use

Because grasses are such a varied group, they can be used for many different landscape purposes. Tall grasses can be used as quick growing screens or hedges. Grasses with striking form, color or flowers can be used as accent plants. Grasses can be used in place of shrubs, in perennial borders and container plantings. They can be used as groundcovers, for erosion control and as edgings. The flowers can be used for fresh or dried arrangements.

Growing Conditions

Grasses are a large group, with varying needs, but some growing preferences are shared by nearly all. Most ornamental grasses must have well drained soil. Raised beds can be used to ensure good drainage. Ordinary garden soil is adequate for most grasses. Some grass-like sedges and rushes will thrive in moist or even wet soil.

Most ornamental grasses need full sun. Some exceptions are northern oat grass, Japanese forest grass, and sedges. Many cool season grasses which require full sun farther north, will prefer some shade during the hottest part of the day in the South.

Planting

While many perennials prefer fall planting in South Carolina, the warm season ornamental grasses will do best if planted in spring. Cool season grasses can be planted in fall. Plant grasses as far apart as they will grow in height at maturity.

Ornamental grasses are usually available grown in containers. If plants are pot-bound, loosen the roots around the bottom and sides of the root ball. Dig the planting hole at least twice as wide as deep. Spread the roots out and refill the planting hole, firming the soil in around the plants roots to avoid air pockets. Be sure the crown of the plant (the point where roots and top join) is even with the soil surface.

Water plants thoroughly after planting to settle the soil around the roots. Pay close attention to watering the first few weeks after planting. While many mature grasses are drought tolerant, they must have a well-established root system to withstand dry periods.

Maintenance

Watering: Once established, moisture needs vary by grass species, soil type, temperature and other factors. Most ornamental grasses will grow best with at least 1 inch of water per week from rain or irrigation. Drip irrigation is an excellent way to water grasses. It saves water by applying water directly to the roots where it is needed, and reduces the chance of foliar diseases.

Fertilization: Most ornamental grasses need very little fertilizer. It is best to base any fertilizer applications on the results of a soil test. Excessive nitrogen in the soil can lead to disease susceptibility, rank growth, and weak stems.

Cutting Back: Cut back grasses before the new seasons growth starts. Since many grasses are attractive in the garden during winter, cutting back can be done in late winter or early spring. Cut stems to a few inches above ground level for best appearance. Grasses can be cut by hand with pruners or hedge shears, with electric hedge shears, or a weed eater with a brush-cutting blade.

Some evergreen grasses do not recover quickly from cutting back. Comb the foliage of these grasses with gloved hands in spring to remove old leaves.

Dividing: Most grasses should be divided every 3 to 4 years. If ornamental grasses are not divided, they eventually become thin or die out in the center. It is best to divide grasses while they are a manageable size. Overgrown grasses can be incredibly difficult to dig and divide.

Dig and divide warm season grasses during early spring, just before new growth starts. Divide cool season grasses in early fall.

Most grasses have very tough, vigorous root systems and may have to be divided with a shovel, saw or ax. Hose off soil to make the roots easier to work with. Separate and replant the vigorous growth on the outer edges of the clump. Replant promptly, never letting the roots dry out. More information on division can be found in HGIC 1150, Dividing Perennials.

Staking: Some tall grasses look best when staked to prevent them from bending or falling over during wind and rain. Reduce the need for staking through variety selection, proper spacing, well-timed division, and avoiding excessive fertilization or water.

Problems

Ornamental grasses have few insect or disease problems. Rust occasionally attacks some cool season grasses, but most plants recover quickly after being cut back. Anthracnose is occasionally a problem. Diseases are most common on plants in improper growing conditions, with low light, poor air circulation or excessive fertilization.

A few grasses can themselves become pests if planted in the wrong location. Be cautious in siting running grasses or confine the root system in a deep bottomless container. Non-native grasses that seed vigorously should be used with care, especially near natural or wetland areas.

Species & Cultivars

Japanese Sweet Flag (Acorus gramineus): Fine grass-like, foot tall semi-evergreen leaves give a texture similar to mondo grass, but thrive in constantly moist, even wet soil. They will also grow in ordinary garden soil in part shade, but need more moisture in full sun.

  • 'Licorice' has evergreen licorice scented leaves.
  • 'Ogon' has yellow leaves that are especially bright in spring and fall, with best color in part shade or shade.

Big Bluestem (Andropogon gerardii): This very tall native grass grows from 3 to 8 feet tall in a narrow clump. The leaves are blue-green in summer, turning rust in fall. It needs full sun and prefers moist to average soil but is very drought tolerant once established.

Giant Reed (Arundo donax): One of the largest grasses, giant reed grows 10 to 20 feet tall. Wide blue-green semi-evergreen to evergreen leaves are arranged along bamboo like stems. Large flower plumes appear in late fall. It can be invasive. It prefers sun and moist well-drained soil, but tolerates wet soil.

  • 'Variegata' has leaves brightly striped with creamy yellow in spring. The leaves fade somewhat by fall. Grows 6 to 12 feet tall.

Korean Feather Reed Grass (Calamagrostis brachytricha): Arching dark leaves form a broad, mounded clump 2½ feet tall covered by tall pink plumes in fall. This species tolerates hot summers better than C. acutiflora. It will grow best in the South in light or part shade, and moist well-drained soil.

Feather Reed Grass (Calamagrostis x acutiflora): This cool season clump forming evergreen grass grows best in the upper Piedmont. It grows narrowly upright 2 to 4 feet tall with slim, tall flower heads in spring that turn golden tan in summer. Sun or part shade.

  • 'Karl Foerster' is strongly upright and early blooming.
  • 'Stricta' is strongly upright.
  • 'Overdam' has white striped foliage turning pink in cool weather. This variety must have part shade and moist soil.

Karl Foerster Feather Reed Grass with mature seed heads
'Karl Foerster' Feather Reed Grass with mature seed heads.
Karen Russ, ©2007 HGIC, Clemson Extension

Japanese Sedge (Carex morrowii): This grass-like plant is grown for its foot tall slender leaves. It grows best in part shade or shade, and moist or wet soil.
  • 'Goldband' is evergreen, with stiff brightly striped white and green leaves.
  • 'Silk Tassel' forms a wide spreading clump of frosted looking thread-like foliage.

Weeping Sedge (Carex pendula): Wide, weeping evergreen leaves form a wide, bright green mound 2 to 2 ½ feet tall. Grows best in part shade or shade in moist, rich soil. Reseeds moderately.

Northern Sea Oats (Chasmanthium latifolium): This native grass thrives in shade. It bears oval flowers prized for dried flower arrangements dangling from 3-foot tall curving stems in fall. Grow in shade or part shade. Prefers moist, rich soil, but tolerates drought once established. Self seeds abundantly.

Pampas Grass (Cortaderia selloana): Very large, tough clumps grow up to 12 feet tall depending on variety and soil moisture. Wide arching leaves with sharp edges spread in a fountain shape topped by dramatic 2 to 3 foot tall flower plumes on long stems in late summer and early fall. Pampas prefers full sun and well-drained soil. It spreads slowly by thick rhizomes to form a huge clump.

  • 'Gold Band' has bright gold edged leaves on a clump only 4 feet tall. Grown mainly for its foliage, as its flowering is sparse.
  • 'Pumila' grows to only 4 feet tall with narrow blue green foliage. The flower plumes are tan, standing 2 ' above the foliage. 'Pumila' is the hardiest pampas grass variety.
  • 'Silver Comet' grows 3 to 4 foot tall with narrow white edged leaves. Plumes rise to only 5 feet.

Weeping Love Grass (Eragrostis curvula): This drought tolerant grass is commonly used for erosion control on highways, but is also very ornamental. Dark green, very fine textured foliage forms dense weeping clumps 1 foot tall and 2 to 3 feet wide. Full sun.

Fescue (Festuca ovina): Fine evergreen foliage forms a low rounded tuft 12 inches tall. This cool season grass grows best in the upper Piedmont in sun or part shade. Well-drained soil. Comb out dead leaves with gloves.

  • 'Elijah Blue' has thread-like, powder blue leaves.

Japanese Silver Grass (Miscanthus sinensis): The species may grow up to 10 feet tall, with large whisk-like flower plumes ranging in color from reddish purple to silver. Prefers full sun and moist, rich, well drained soil, but will tolerate some drought once established. It often reseeds and can be invasive near natural areas. Avoid planting the straight species, which is most likely to be invasive.

  • 'Adagio' is one of the smallest cultivars, growing to only 36 inches tall in a tight mound of fine green foliage. Abundant flowering in late summer
  • 'Cabaret' has centrally white-striped, wide leaves on a strong, self-supporting 6 foot tall plant. Purplish flower heads in early fall mature to tan.

Bold white stripes on Cosmopolitan Miscanthus leaves
Bold white stripes on 'Cosmopolitan' Miscanthus leaves.
Karen Russ, ©2007 HGIC, Clemson Extension

  • 'Cosmopolitan' has white striping on the edges of its wide leaves. Strong, non-floppy habit.
  • 'Gracillimus' has narrow leaves with a silver midrib, Five to 6 feet tall plants tend to flop unless staked. Good orange to buff fall color.

Slender leafed Morning Light Miscanthus
Slender leafed 'Morning Light' Miscanthus
Karen Russ, ©2007 HGIC, Clemson Extension

  • 'Morning Light' is a strongly upright plant to 4 feet tall. The slender leaves appear silvery gray green due to fine white striping. Flower plumes are red on opening, fading to soft tan.
  • 'Purpurascens' grows in a tight, upright clump 3 to 4 feet tall. The leaves are green with a red tint, turning brilliant red orange in fall. This variety performs best in the Piedmont.
  • 'Strictus' (Porcupine Grass) is an improved, strongly upright form of zebra grass, growing to 6 feet tall. It also has bright yellow, horizontal bands across the leaf.
  • 'Variegatus' has 5 foot tall brightly white striped foliage. This variety will have best color if planted in light shade. It needs to be staked for best appearance.

Hairgrass (Muhlenbergia capillaris): Clouds of tiny flowers form a pinkish-purple haze appearing in October and fading to tan through the winter on this showy native grass. Clumps of very fine, blue-green to gray-green foliage rise to 2 to 3 feet tall. Full sun, extremely drought tolerant once established.

Hairgrass in full fall flower color
Hairgrass in full fall flower color.
Karen Russ, ©2007 HGIC, Clemson Extension

Bamboo Muhly (Muhlenbergia dumosa): Arching bamboo like stems with billowy light green foliage, grow 5 to 6 feet tall. Bamboo muhly is an excellent non-invasive substitute for bamboo. Full sun, drought resistant once established.

Switchgrass (Panicum virgatum): This beautiful native grass has many varieties with showy flowers, excellent fall color and winter interest. Switch grass prefers full sun in moist to wet soil, but is highly adaptable. It reseeds occasionally, but not invasively.

  • 'Cloud Nine' has light blue foliage growing 6 feet tall with large airy flower heads rising another 1 to 2 feet in mid to late summer.
  • 'Heavy Metal' has a strongly upright, narrow habit with airy flowers and 3 to 4 feet tall metallic blue foliage that turns yellow in fall.
  • 'Shenandoah' has deep green leaves tipped with purple in summer, turning burgundy purple in fall. Flowers are reddish pink. This variety grows to only 3 to 4 feet tall. This and the following cultivar are excellent substitutes for the invasive Japanese blood grass, a type of cogongrass.

Rotstrahlbusch Switchgrass summer leaf color
'Rotstrahlbusch' Switchgrass summer leaf color.
Karen Russ, ©2007 HGIC, Clemson Extension

  • 'Rotstrahlbusch' is similar to 'Shenandoah' with a somewhat more upright form, and is a bit smaller and narrower.

Fountain Grass (Pennisetum alopecuroides): Beautiful, cream to pink, bottle brush shaped flower heads appear from mid to late summer above fine, arching mounded foliage 3 to 4 feet tall. Prefers sun and moist but well drained soil. Fountain grass reseeds and may be invasive into natural areas.

  • 'Hameln' is compact, growing to only 2 feet tall. Performs best in the Piedmont.
  • 'Little Bunny' grows to only 1 foot tall.
  • 'Moudry' has striking black flower spikes in late summer to early fall. It grows 2 to 3 feet tall. This variety reseeds abundantly.

Chinese Fountain Grass (Pennisetum orientale): Soft pink or white flower spikes appear from late spring through fall above blue green foliage only 1½ feet tall. It spreads slowly by rhizomes, but rarely reseeds.

Annual Fountain Grass (Pennisetum setaceum): While it must be grown as an annual throughout South Carolina, it grows 4 to 5 feet tall by summers end. Striking purplish pink flowers above slender green foliage are produced continuously through summer. Prefers sun and moist, well-drained, fertile soil.

  • 'Rubrum' (Red Fountain Grass) has dark burgundy-red foliage and bloom spikes.
  • 'Rubrum Compacta' grows 2½ to 3 feet tall, with even finer foliage, but is not quite as red.
  • 'Burgundy Giant' is a hybrid with very broad, deep red foliage and maroon flower spikes. It is robust and grows 5 to 6 feet tall.

Little Bluestem (Schizachyrium scoparium): This native grass, also called broom sedge, grows to 3 feet tall, with fluffy flower spikes in mid fall held well through the winter. Upright, light green foliage turns orange tan in fall. Prefers full sun and tolerates almost any soil.

  • 'The Blues' has very blue leaves to only 1½ feet tall. It has very bright orange fall color.

Indian Grass (Sorghastrum nutans): This adaptable tall, upright native grass blooms with narrow, dark gold flower plumes in late summer.

Indian grass (Sorghastrum nutans) along sunny roadside.
Indian grass (Sorghastrum nutans) along a sunny road.
Joey Williamson, ©2014 HGIC, Clemson Extension

Foliage turns golden tan in the fall. Prefers full sun and rich, moist well drained soil, but tolerates most soil. Plants reseed, but are not invasive. Indian grass is the state native grass of South Carolina.

  • 'Sioux Blue' has stiff, upright blue-gray foliage.

Prairie Dropseed (Sporobolus heterolepis): Very fine-textured leaves arch to form a wide clump 2 feet tall. Filmy flowers appear in late summer, well above the leaves. Prefers full sun and well drained soil. Very heat and drought tolerant once established.

Giant Needle Grass (Stipa gigantea):The flower stems are very tall, arching and airy, with gold dangling flowers in early to mid summer. Narrow evergreen foliage grows 2 tall. Prefers sun with moist, well drained soil.

Texas Needle Grass (Stipa tenuissima): Exceptionally fine textured evergreen leaves grow in a weeping mound. Fine billowing flower spikes appear in summer. Prefers sun and dry soil, avoid excessive water once established

Sea Oats (Uniola paniculata): This major native Southern beach grass tolerates harsh growing conditions and stabilizes dunes. Gray-green sharp leaves grow 3 to 8 feet tall topped by arching flower stems. Prefers full sun and well drained sandy soil. Do not fertilize sea oats. Never collect or purchase wild collected plants.

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