Ornamental Grasses – Low Maintenance/ High Drama

Mexican Feather Grass and Vervain

by Brian Oleksak, County College of Morris

One of the most exciting trends in landscape horticulture in the past few years has been the rediscovery and new introductions of ornamental grasses in the marketplace. The old standards of fountain grass, feather reed and Chinese silver grass still play a role in designs, but the palette is much broader now for creative designers. The desire for a greater use of native species, curbing the spread of invasive plants and the inspirational designs by European visionaries who recognized the natural beauty of North America launched an aesthetic trend that is changing the industry.

Grasses are members of the Poaceae family, a family of monocots with a worldwide distribution. From a horticultural perspective, we tend to group the various genera as cool season and warm season in their seasonal performance. As the name implies, cool season grasses are physiologically active and growing during cooler seasons, particularly the spring and fall. Warm season species, like switch grass, blue grama and prairie dropseed, are most active during the heat of the summer and actually emerge in the springtime three to four weeks after their cool season counterparts. Landscape maintenance professionals should be aware of this growth habit as the customer may assume that the grasses did not overwinter. Simply assure the customer that these species will reemerge when soil temperatures get warmer.

One of the best arguments for including ornamental grasses into a landscape design is the ease of care and maintenance. When considering the selection of any landscape plant we should always ask “Where is the plant found in nature?” Selecting the right plant for the right place always takes into consideration the plant’s evolutionary history and adaptation to its environment. Grasses evolved on prairies and open grasslands in full sunlight, frequently undergoing periods of droughty conditions. When used in residential and commercial designs grasses require full sun and welldrained soil conditions for best performance. Few grass species tolerate shaded locations; the exceptions being Japanese forest grass (Hakonechloa macra) and Northern sea oats (Chasmantium latifolium) which will tolerate semishaded conditions. Designers seeking a grassy look for shaded locations should instead explore the possibilities of using sedges (Carex species) of which there is a vast array of new introductions on the market. Landscapers should avoid supplemental irrigation and excessive fertilizer as these practices may encourage overly lush growth and weak stem strength causing the grasses to flop over after a heavy rain.

Yearly maintenance of ornamental grasses is minimal, making them perfect candidates for use in commercial designs and sprawling housing developments. Grasses need to be cut back once per year to remove last year’s display and allow for the emergence of the current season’s growth. The landscape maintenance professionals and their clients can work out the details as to when this happens. Some people prefer to leave the grasses standing for the winter to provide interest in an otherwise barren landscape. For these clients cutting back grasses is part of the spring cleanup regime. Some professionals prefer to cut them back in the fall in anticipation of heavy snowfall and winter maintenance activities. Either practice is acceptable as it will not affect the growth of the grasses in the future.

Grasses are a perennial feature of the landscape and require little care beyond seasonal cutbacks. However, after several years on the site you may discover a dead zone originating in the center of an established grass clump. Should this happen you should dig up the clump, cut out the dead area, divide the vigorous portions and replant them.

As features in a design grasses offer many possibilities for softening hardscape elements, blending with the existing environment, reintroducing native species and creating a sense of rhythm and movement with their soft, billowy forms. A key to the effective use of grasses is to mass them in the landscape. With the exception of a truly large species like Chinese silver grass (Miscanthus sinensis), a solitary grass clump is not sufficient to hold its own in a design. Massing an area with grasses recalls their origin and makes a bolder impact. Grass forms include the strong verticals of switch grass (Panicum virgatum) and Indian grass (Sorghastrum nutans), the arching tufts of prairie dropseed (Sporobolus heterolepis) and the frothy waves of Mexican feather grass (Nasella tenuissima, formerly Stipa) and purple love grass (Eragrostis pectinacea).

Blue Grama

Photo: Brian Oleksak

Color changes offering four-season appeal is another great attribute to consider. Many of the native ornamental grasses such as switch grass, big bluestem (Andropogon gerardi) and little bluestem (Schizacyrium scoparium) begin the growing season with blue-green foliage, which changes to tones of red and russet in the fall finally settling on straw-colored winter display. The inflorescences (“flowers”) of grasses also add texture and nuance to the seasonal changes of a planting. Inflorescence forms range from narrow spikes and racemes to billowy, cloud-like panicles. The inflorescences of blue grama (Bouteloua gracilis) appear like little flags held above the tufted foliage. By careful selection of grasses by their habit, form, colors and textures you can greatly enhance the year-round appeal of a landscape design.

Mixed Perennials, Olympic Park

Photo: Brian Oleksak

Grasses to consider in your next landscape design plan (including hardiness zones)

• Switch grass (Panicum virgatum), ‘Northwind’, ‘Heavy Metal’ Zones 3-9

• Big bluestem (Andropogon gerardi), ‘Indian Warrior’, ‘Red October’, ‘Windwalker®’ Zones 3-9

• Little bluestem (Schizacyrium scoparium), ‘Standing Ovation’ Zones 3-9

• Mexican feather grass (Nasella tenuissima) Zones 7-10

• Blue grama (Bouteloua gracilis), Zones 3-9

• Side-oats grama (Bouteloua curtipendula) Zones 3-9

• Prairie dropseed (Sporobolus heterolepis), ‘Tara’, a dwarf variety, Zones 3-9

• June grass (Koeleria macrantha) Zones 3-9

• Sweet grass (Hierochloe odorata) Zones 3-7

• Bottlebrush grass (Elymus hystrix) Zones 3-8

Little bluestem ‘Standing Ovation’

Photo: Rutgers Gardens

Brian Oleksak is Associate Professor and Chair of the Landscape and Horticultural Technology Department at the County College of Morris in Randolph, New Jersey. Professor Oleksak teaches courses in woody landscape plant and herbaceous plant identification, soils, arboriculture and botany at CCM. He holds a B.S. in Agronomy from Penn State University and an M.S. in Ornamental Horticulture from Ohio State University. Professor Oleksak resides in Newton, New Jersey.

Brian Oleksak