Ornamental Grasses, Part II

Last month’s article dealt with ornamental grasses in general. This month we look at some of the more popular and useful grasses for Missouri gardens.

Description of Popular Species
Blue Fescue (Festuca ovina var. glauca) is a cool-season, clump forming grass with attractive silvery- blue foliage native to Europe. It exhibits a low, tufted growth habit and reaches a mature height of between six and ten inches. Its flower is of little ornamental value and should be removed. Blue fescue thrives in full sun or partial shade and is tolerant of dry conditions. The more sun it receives, the deeper will be its blue color. Because of its small size it most often is used as a edger or planted in mass for a ground cover effect. It is subject to summer die-back under very hot conditions or in poorly drained sites. The cultivar ‘Elijah Blue’ is preferred over the species because of its superior blue color.

Feather reed grass (Calamagrostis arundinacea) is a cool-season, clump forming grass native to Europe. It has a fairly upright habit of growth to a mature height of about 36 inches. Its leaves are dull green in color, course to the touch and about one-half inch in width. Feather reed grass bears flowers in early summer in the form of greenish panicles that mature to a straw or buff color. Its flowers are about 15 inches long and held in a fairly tight cluster just above the foliage and retain ornamental value late into the winter. Feather reed grass thrives in full sun in nearly any type of soil. Although it appreciates a good garden loam, it is one of the few ornamental grasses that will tolerate heavy soils or moist, poorly drained areas. It is considered by many to be one of the best medium-sized ornamental grasses and can be used as a specimen or planted in mass. The cultivar ‘Karl Foerster’ produces pinkish panicles that mature to a golden-tan and is superior to the species in ornamental value.

Fountain grass (Pennisetum alopecuroides) is a warmseason, clump forming grass native to China. It exhibits a graceful, arching habit of growth to a mature height of about 36 inches. Fountain grass has leaves that are about one-fourth of an inch wide and turn from a bright green during the summer to a golden brown in the fall. In mid- to late summer it bears five to seven inch spikes that resemble somewhat a bottle brush in appearance. Its flowers are not particularly long- lived and cannot be dried. Fountain grass prefers a full sun exposure in a well-drained garden loam. Because of it medium size and graceful appearance, it makes an excellent border plant. ‘Hameln’ is a particularly desirable cultivar that matures to a height of between 24 and 36 inches and blooms profusely in good conditions.

Giant Chinese silver grass (Miscanthus floridulus) is a warm-season, clump forming grass native to China. It has an upright, arching habit of growth to a mature height of between 10 to 14 feet. Its leaves are glossy green with a distinct white (silver) midrib and are about one to one and one-half inches in width and up to two and one-half feet long. Its cane-like stem (culm) can achieve a mature diameter of up to two inches. Giant Chinese silver grass bears reddish-brown panicles in early fall held about 24 inches above its foliage. Flowers dry to a light straw color and retain ornamental value well into the winter. It prefers a full sun exposure in a fertile, moist soil and is quite tolerant of hot weather. Giant Chinese silver grass needs room in the garden because of its large size. It can be incorporated as a background specimen in a planting of ornamental grasses or taller perennials or used to form an effective hedge or screen. There are no named cultivars.

Indian grass (Sorghastrum nutans) is a warm-season, clump forming grass and is one of North America’s most attractive native grasses. It is a major component of "tallgrass prairies" still found in sections of the Midwest. Indian grass has leaves that are about three-eights of an inch wide and eighteen inches long with attenuate tips and glabrous surfaces. Foliage typically turns to a burnt orange color in the fall. It displays a large, arching habit of growth and matures to a height of up to six feet. It bears a narrow panicle as a flower in late summer that adds interest to the plant until early winter. Indian grass prefers a full sun exposure and tolerates a variety of soils, although it prefers a deep, moist garden loam. It is considered to be both heat and drought tolerant. It is useful in massed plantings in naturalized areas or in the rear of large ornamental borders. Indian grass also is useful in stabilizing soil in areas where erosion is a problem. There are no named cultivars.

Japanese blood grass (Imperata cylindrica var. rubra) is a warm-season, spreading grass native to Japan. It is distinguished by its uniquely colored, blood-red leaves that are about one-half of an inch wide and has an upright and somewhat arching habit of growth to a mature height of between 12 and 18 inches. Its flower is not significant. It tolerates full sun or partial shade equally well but must have well-drained soil in other to thrive. Japanese blood grass spreads fairly rapidly but is not considered to be overly aggressive in the garden. It usually is massed in the border for its brilliant color but can be used in tubs or containers as well. ‘Red Baron’ is meritorious cultivar that is preferred over the species because of its superior color.

Maiden grass (Miscanthus sinensus ‘Gracillimus’) is one of the most popular ornamental grasses because of its narrow, graceful leaves that move gently in even the slightest of breezes in the garden. It is a warm-season, clump forming grass whose parental species (M. sinensus) is native to Japan. Maiden grass has narrow leaves about onefourth of an inch wide with a distinctive white midrib and forms a very graceful, arching clump about 48 to 60 inches tall. It bears copper-colored panicles about 12 to 15 inches in height and held about 12 to 15 inches above its foliage in late September. The panicles dries to a silvery-white color and "fluffy" texture after maturity and adds interest to the plant well into the winter. Maiden grass prefers a full sun exposure in a moist, fertile garden loam. It needs to be divided every third or fourth year in order to keep the center of the clump from dying. Numbers of other named cultivars have been selected from Maiden grass but ‘Gracillimus’ remains the most commercially available and widely planted.

Northern sea oats (Chasmanthium latifolium) is a warmseason, clump forming grass native to North America. It displays a fairly upright and somewhat arching habit of growth and produces a mature clump about 30 to 36 inches in height. Leaf blades are about three-fourths of an inch wide, flat and glabrous except for their rough margins. Northern sea oats derives its common name from its flowers which are drooping panicles about five to ten inches long that contain spikelets about one inch in length hanging from thread-like pedicels. The overall effect of the flower is quite striking and not unlike the appearance of dangling green jewels that change from green to a reddishbronze color at maturity. Flowering occurs in late summer and flowers remain attractive throughout the winter giving this grass three seasons of effect. Northern sea oats prefers a full sun exposure and fertile, well-drained soil. However, it is one of the more shade tolerant ornamental grasses but will produce taller plants in shadier conditions. It enjoys a variety of uses including borders, water gardens, naturalized areas and for drying the flowers. There are no named cultivars.

Plume grass (Erianthus ravennae) is a warm-season, clump forming grass sometimes referred to as hardy pampas grass. Although very attractive, true pampas grass (Cortaderia sellioana) is not reliably hardy past zone 8 and is not a wise choice for the Midwest. Plume grass is native to Europe and reaches a height of up to 14 feet when in bloom with an upright, arching growth habit. It has leaves that are V-shaped and about one inch wide with a distinctive, white mid-rib. Both surfaces of the leaf are coarsely pubescent giving them a raspy feel. The flower is a large, showy panicle on stout pedicles well above the foliage. They appear in late summer to early fall and change to a buff-gray color and "fluffy" texture upon maturity and are quite showy well into the winter. Plume grass prefers a full sun exposure and well-drained soil; heavy soils are to be avoided. It can be used as a specimen in the landscape because of its interesting architectural form or planted in mass to form an effective screen. The panicles dry easily and are useful in flower arrangements. There are no named cultivars.

Porcupine grass (Miscanthus sinensus ‘Strictus’) is a warm-season, clump forming grass selected from a species native to Japan. It is unique from other cultivars of because (M. sinensus) because of the bright yellow, horizontal variegation on its leaves (somewhat resembling the bands on the quills of a porcupine). Leaves are up to one-half of an inch in width and held fairly upright producing a stiffly arching clump that achieves a mature height of about 48 to 60 inches. It flowers in late summer and produces a copper-colored panicle about 12 inches in height and very similar to that of Maiden grass; it dries to a buff color upon maturity and remains attractive well into the fall. Porcupine grass prefers a full sun exposure in a moistureretentive, fertile garden loam. It makes a dramatic effect in the garden because of its bright, horizontal variegation and is used both as a specimen plant or in mass plantings. It is a close "look alike" to Zebra grass (M. Sinensus ‘Zebrinus’) which has a more graceful, arching habit of growth but is a bit less winter hardy than Porcupine grass. Another cultivar (M. Sinensus ‘Variegatus’) is similar in size and nature to Porcupine grass but has leaves with attractive, white variegation that is longitudinal rather than horizontal. It has a very graceful, arching growth habit.

Purple fountain grass (Pennisetum setaceum ‘Rubrum’) is a warm-season, clump forming grass native to Africa. Hardy only to zone 8, it is treated as an annual grass in the Midwest but worth replanting each year because of its colorful leaves and flowers. It produces burgundy-purple leaves about one-half of an inch wide that form a graceful arching clump that achieves a mature height of between 36 and 48 inches. The flower is a colorful, dark purple plume eight to twelve inches in length with a bottlebrush appearance. It flowers profusely from June through frost. Purple fountain grass prefers a full sun exposure in moisture-retentive yet well-drained soil. It is very effective as a specimen plant in the center of an annual bed or can be used to add height and volume to a border. Although it prefers adequate moisture, it is extremely heat tolerant and adds excellent color and texture to the garden.

Ribbon grass (Phalaris arundinacea var. picta) is a warm-season, spreading grass native to North America and Europ. Its colorful, green and white variegated leaves are about two-thirds of an inch wide and six to twelve inches long. The green and white colors are about equal in amount giving the leaves a ribbon-like appearance. Its flowers appear in early summer but are not of significant ornamental value. Ribbon grass rapidly spreads to form a loose, somewhat open ground cover between 18 and 24 inches in height. It is tolerates full sun or partial shade and thrives in nearly any type of soil. Ribbon grass makes an effective, colorful ground cover because of its aggressive habit of growth. If planted in a border it should be planted in a bottomless container sunken into the soil to control its spread. Because of its ability to tolerate wet soils it is very effective in holding soil in place along stream banks. Silver banner grass (Miscanthus sacchariflorus) is a warm-season, spreading grass native to China. It has medium-green leaves about five-eights of an inch wide and up to ten inches long borne on stout, upright culms. Like many other members of the Miscanthus genus its leaves are distinguished by a pronounced white midrib. Leaves have the added attraction of turning an attractive reddish-orange color in the fall. Silver banner grass produces silvery panicles about eight to ten inches in height in mid-summer that are held well above its foliage and are effective into the fall. It thrives in a full sun exposure in moist-to-wet soil and spreads rather rapidly via rhizomes to form a dense, upright mass of foliage about 48 to 60 inches in height. Because of its affinity for moisture, silver banner grass is excellent for massing along water features and is excellent for soil stabilization along stream banks. It is invasive and should not be planted close to desirable species without containment. There are no named cultivars of this species.

Switch grass is a Missouri native ornamental grass which was an important component of the tallgrass prairie which once covered large areas of the State. Photo courtesy of Missouri Botanical Gardens.

Switch grass (Panicum virgatum) is a warm-season, clump forming grass native to North America and another of the "tallgrass prarie" grasses. It produces flat, glabrous leaves about five-eights of an inch wide and between 24 to 36 inches long; growth form is tall and arching or mounded to a height of between 48 and 72 inches. Switch grass produces fine-textured, delicate panicles about 24 inches long in mid- to late summer that are purplish upon emergence and mature to a beige color. It prefers full a sun exposure in moisture retentive soil but will tolerate some shade and dry soil. Switch grass is best used in masses or for living screens. There are several named cultivars available (e.g., ‘Rehbraun’) selected for shorter height and pigmented (usually red or purplish) foliage.

David Trinklein
Associate Professor Plant Sciences