Ornamental Grasses: Grasses have always been the predominate part of our native prairies. We are most familiar with the use of them in the landscape as ground covers, or what we would normally refer to as lawns. However, when used in the landscape certain varieties of grasses can add a great deal to the texture, color, motion and even sound of the garden. They can be used as individual specimens, in mass plantings or as border plants. Many of them are also a good source of dried materials for arrangements.
Due to our northerly location we are somewhat limited as to the varieties that are perennial. Even though Pampas Grass (Cordateria selloana), which has been the ornamental grass that is most familiar to all of us, is not hardy in Montana or most of the plains, there are still a number of highly ornamental grasses that can add beauty to the landscape and garden.
The following are some of the more ornamental grasses that are available for planting. The perennial cultivars will benefit from winter protection provided by a good snow cover or mulch to increase their hardiness. Grasses are all relatively insect and disease-free and require a minimum of maintenance. Trimming, or cutting back, the old, dried foliage in spring is about all that is required.
Medium growing upright perennial that prefers sun and blooms in May. It has a height of 2-3′ and spread of 2-3′. The flower heads resemble snake rattles. Needs to be watered and mulched in the winter. May need to planted every year.
Calamagrostis acutiflora ‘Karl Foerster’
(FEATHER REED GRASS)
2001 Plant of the Year. This very popular grass begins to flower in June and the show doesn’t stop until you cut it back in the late Fall or early Spring. The erect 6 foot plumes splay gracefully after a rainstorm or dusting of snow, and then return upright again when they dry. This grass grows 3 to 7 feet in sun or part shade. One of the best all around grasses. It is trouble free, not fussy about soil, withstands drought and provides a long season of interest. Zone 4.
Grasslike, clumping plants grown for foliage effect in borders, rock gardens, containers, and water gardens. Long, narrow leaves are often striped or oddly colored. Many interesting cultivars are available. Most are annuals in our climate.
(TUFTED HAIR GRASS)
Deep green tufted grass that grows to two feet. A cool season, evergreen grass that is hardy in Zone 4. Also worth trying in Zone 3. Normally found in moist, boggy sites and will do best in a moist site in partial shade. Produces delicate flowers in June that rise two feet above the plant and remain showy into winter. Because of the fine texture of the flowers it is best used in mass to enhance the effect of the flowers.
(BLUE LYME GRASS)
This 2-3′ tall grass is a vigorously spreading perennial with distinctive metallic blue foliage. Makes a quick ground cover for rough areas. Plant in full sun for brilliant foliage color. In the landscape, this grass is a beautiful contrast to purple foliage. Cut back faded foliage in Winter or Spring to tidy plants.
This grass, with its steel-blue clump of leaves is just the answer if your landscape is experiencing a blue shortage. The leaves are the attraction, the flowers are not significant.
(RAVENNA GRASS or HARDY PAMPAS GRASS)
This imposing vertical grass sports shiny silver plumes with a stout central rachis held 4 to 5 feet above the basal clump of 1 inch wide leaves which are 4 feet high. Makes a good screen or accent plant. Zone 5-6.
Small six inch tall grass with attractive, fine-textured, blue foliage. Cool season grass that is hardy in Zone 4. It flowers profusely on erect stems to 15 inches, which fade to a pleasing light tan. In hot spells the foliage may brown out but revives with the onset of cooler weather.
(BLUE OAT GRASS)
Medium growing mounding perennial with oat like flowers. It likes sun and blooms beginning in summer. Height 2-3′ with a spread of 2-3′. Best used as accent or in rock garden, very attractive and adaptable. They combine well with other grasses and broadleafed plants, and with boulders in rock gardens. Groom by pulling out occasional withered leaves. Hardy in all zones.
(GREATER WOOD RUSH)
Compact mounding perennial with chestnut brown flowers. Likes partial shade or shade, blooms in April with a height of 1′ and spread of 1-2′. Prefers good moist soil. Finest of the wood rushes for ground cover.
(GIANT CHINESE SILVER GRASS)
This upright broadleaf grass grows to a height of 8 to 12 feet with a spread of up to 5 feet. Grow in sun. Forms a graceful screen. Flowers with towering tassels that mature from reddish-tan to silver.
Miscanthus sinensis Cultivars
(MAIDEN OR EULALIA GRASS)
Warm season grasses that are hardy into Zone 4. Most grow to about 4 feet , and many have striking variegation, banding or striping. Upright grower. All bear showy flower plumes in silver or rosy hues in the late Summer or Fall. In Fall the three-quarter inch wide leaves color to a bright red-orange before fading to a silken white in Winter. Forms a large clump in time, a ten-year old specimen can be 30 inches or more across. Needs full sun.
(PURPLE MOOR GRASS)
Rapid growing upright perennial with brownish purple spike flowers. Likes sun and blooms in June. Height 1-2′ with a spread of 1-2′. Prefers good moist soil. The flowers stand 3′ above foliage. Water and mulch in winter. A variegated cultivar is also available.
Molinia caerulea arundinacea ‘Windspiel’
Large grass that forms green clumps of four to five feet in width and two to four feet in height. Delicate, wire fine yellow seed heads are borne on stems of up to seven feet in July and August. Hardy in Zone 4. Best planted where it will have space to develop and against a plain background so the fine seed heads can be appreciated. Will tolerate light shade but prefers full sun.
Panicum virgatum Cultivars
Shorter and more upright form of the native species. Most reach up to five feet when in bloom. Slight blue cast to foliage. Hardy in Zone 4. A sod forming grass, Switch Grass quickly develops into a bushy plant in the garden. The fine-textured, airy flower heads are produced in late summer and turn a warm, glowing wheat color in winter. Should be cut back in early spring. Prefers full sun.
(PURPLE FOUNTAIN GRASS)
Rapid growing upright with dark green, narrow leaves forming clumps with flowers arching above. Flowers are round, like bottle brushes, and very showy. Likes sun and blooms beginning in late Summer. Height of 3′-4′. Use in dry locations, as in gravel beds, or as a focal point in low ground covers. Drought resistant.
Phalaris arundinacea picta
Strongly rhizomatous grass that forms a spreading clump of 18 to 24 inches in height. Very attractive highly variegated green and white leaves. Will do well in most any soil and withstand drought particularly well. Prefers sun. Hardy in Zone 3. Spreads aggressively.
The above cultivars represent only a few of the many ornamental grasses that are available to plant in our area.