The Seed is the horticultural magazine of the Nebraska Statewide Arboretum. It is published twice a year for the members of the Arboretum. This issue was written by Karma Larsen. Copyright 2000. For a full version of this publication with visuals, photographs, charts, landscape designs, etc. call 402-472-2971.

The Seed, Fall 2000

Ornamental Grasses

"The garden of the future will host many native plants; grasses will play a very important role because of their diversity and adaptability. The door is open to a more varied and natural approach to landscape design. I envision a broadening of landscape designs away from the straight-lined, evenly spaced planting to one of fluid, dynamic, and constantly changing beauty."
Kurt Bluemel, Past President, Perennial Plant Association

      Grasses dominate Nebraska's wild places, but only in recent years have taller grasses been included in our gardens. We associate grasses with the countryside, and by including them with other plants in our gardens, we draw some of the countryside in with them and immediately connect them to the larger landscape surrounding it, giving it the sense of appropriateness most of us strive for.
      Because of their adaptability and the great variety in shape and size of ornamental grasses, their use is almost unlimited. They make excellent specimen plantings, interesting enough to stand on their own as a focal point in the garden.
Taller grasses can function as a hedge, providing a green backdrop to perennial beds and screening out unwanted views. Since most reach full height in their second growing season, they can create an almost immediate barrier. New plantings of slower-growing trees and shrubs can be quickly and temporarily filled in with grasses that can be removed or allowed to decline in the shade of the woody plants as they get established.
      The softness of their texture and loose, informal growing habit enable them to pull together plants that might otherwise contrast. For delicate, ephemeral flowers, grasses offer a striking complement and provide support and extended interest when the less hardy perennials are not at their peak. Shorter grasses work as groundcovers, crowding out weeds.
      A very important characteristic of ornamental grasses is their ability to soften the hard surfaces of the urban environment-sidewalks, buildings, parking areas and pathways. Michael King and Piet Oudolf, the authors of Gardening with Grasses, write "Landscape architects have long appreciated the powerful qualities of ornamental grasses, particularly in relation to modern rectilinear buildings… they have the strength of form to complement such situations without detracting from a building's visual presence. Nevertheless, they are alive, they move, and subtly soften a building's impact upon its surroundings and even the way it connects with the ground."
      Pathways are significantly softened by growing grasses alongside them. Functional metal railings become less obtrusive when grasses arch through them. Hard, straight-edged walkways can be softened by a fluid border of grasses, changing them from utilitarian routes into meandering walkways.
They can be used in very formal gardens and in the most informal prairie plantings. At the University of Nebraska-Lincoln's city campus, mass plantings of little bluestem can be found in Sheldon Memorial Sculpture Garden; and within a block away cropping up in the midst of other prairie plants at Cather Garden… very different usage, very different effect.

Texture, Movement & Translucency
      No designer would recommend a garden made up exclusively of grasses, but including even a very small planting of grasses in a landscape affects the way we see associated plants and heightens our awareness of other elements of the environment. Though they shift the emphasis of the planting away from color, in some ways they actually intensify the way we see color, just as one red flower in the midst of a prairie can arrest our eye as much an entire bed of brightly colored annuals.
      Grasses derive much of their beauty and interest not strictly from their own characteristics but from the way they respond to wind and light and snow and ice, drawing our attention to more subtle characteristics like texture, movement and translucency.
      Probably more than any other ornamental, grasses are translucent, allowing light to filter through foliage and feathery seedheads. Landscape designers take full advantage of this characteristic, planting them in highly visible areas where the low angle of fall and winter sunlight provide dramatic back-lighting.
      Late fall and winter, in fact, are the times when these plants shine, whether illuminated by sunlight or not. Snow, frost and ice adhere to their feathery seedheads and provide unparalleled midwinter beauty, extending their interest and beauty all the way from late spring when new shoots emerge through early spring when old growth is removed. The tan and buff colors of winter grasses, provide a soft backdrop for the darker colors and structures of other perennials left standing till spring.
      Even wind and snow, powerful elements that have to be taken into account in any Nebraska garden, rarely do permanent damage to these hardy plants. A nurserywoman in Illinois writes "I've seen a Miscanthus bowled over by a winter snow and when the snow melts, it springs back up. It can tolerate heavy snow and hold its form pretty well." Because of this, she recommends it to people who are "sick to death of junipers and are looking for something different."
In striking contrast to the damage it can do to other plants, wind actually benefits a garden with grasses. For some gardeners, the sound and visual effect of grasses responding to the movement of wind is their primary reason for planting them.
      In a water garden, grasses stabilize the edges and mimic their occurrence in the wild where rivers, ponds and lakes are almost always surrounded by a grassy fringe. Though a pond or pool may seem very different from the hard surfaces of a building, King and Oudolf believe that grasses soften and integrate these still planes in much the same way they do any hardscape element: "Ornamental grasses are able to blur the line marking the edge of a water feature and unite it with the surrounding landscape. Even when the hard edge of a formal pool is obscured in just one spot by a clump of reeds, a significant natural element is introduced. This powerful effect can be exploited by gardeners when integrating an overtly unnatural water feature, such as a swimming pool, into an otherwise natural garden design."
      Sedges, rushes, cattails, eulaliagrass and switchgrass are good choices for water gardens. Cascading grasses can be used as a substitute for, or to reinforce the visual and even sound effects of, a waterfall.

Planting and Care
      Grasses can be established from seed or transplants, but it can take take many years to produce a good-sized clump of grasses from seeds and you may end up with far more plants than you have use for.
      It's best to plant grasses when they are growing vigorously, so the best time to plant is spring or early summer, when root growth is at its peak. But plants with a substantial root system can be put in almost any time during the growing season. If you are dividing existing plants, the larger the division is, the hardier the new plant will be. New grasses should be spaced apart approximately half of their mature height from other plants or grasses.
      Don Steinegger, University of Nebraska-Lincoln horticulturist, recommends "incorporating organic matter into the root zone to improve water-holding capacity and oxygen levels, particularly if the soil is compacted." He also recommends testing the soil and adding phosphorous, potassium, calcium or sulfur to the root zone before planting, if necessary, since "these nutrients will not move into the root zone if applied only to the soil surface."
      Most ornamental grasses will grow adequately with three to five hours of sunlight, but will grow stronger and more upright in full sun. Except in very rare occasions fertilizer is unnecessary and, in most cases, detrimental, causing plants to grow rapidly and fall over. Mulching, likewise, can harm rather than help some ornamental grasses, providing an environment that makes the plants susceptible to rot and disease.
      Though new grasses require regular watering, after becoming established they are far more likely to be hurt by over-watering rather than by a lack of watering.
Ornamental grasses are almost pest- and disease-free. Rusts can usually be controlled by allowing plenty of air movement. There are some new pests that are damaging to Miscanthus species, the Miscanthus mealybug and Miscanthus blight. Discarding diseased plants is the best way to eliminate these problems.
In a prairie planting or in areas with lots of grasses, Bob Henrickson of State Fair Park Arboretum in Lincoln recommends combining cool and warm season grasses (e.g. sedges with Canada wild rye, prairie dropseed and little and big bluestem) so that periods of spring growth, seedhead formation and fall color overlap. Besides the earlier spring growth the cool season grasses provide, they also compete with weeds while warm-season grasses are still dormant.
      One concern gardeners may have is that the grasses will become invasive, and some ornamental grasses are aggressive, but for the most part ornamental grasses can be kept in bounds by mowing. Clumping grasses like blue fescue and switchgrass are far less likely to become invasive, whereas cord grass and giant reed, which spread by runners, can rapidly overtake other plants. Miscanthus and Pennisetum species include both running and clumping varieties.
One option for aggressive varieties, if they're ones you would like to include in your garden, is to plant them in containers. Areas confined by hardscape can also provide needed boundaries.
      With their abundant seed production, many gardeners worry about the spread of grasses through seeds but few gardens have ideal conditions for grass seed germination.
      For the most part, maintenance consists of a once a year cutting in late winter or early spring; to within 3-4" of the ground for most grasses. This can be done in a number of ways, with hand pruners, manual or electric hedge shears, a bow saw. String trimmers and chain saws can also be used, but make cleanup far more difficult. Tracy DiSabato-Aust, author of The Well-Tended Perennial Garden, recommends tying up the grass beforehand to make cleanup even easier. She also recommends wearing gloves, as the blades of many grasses are razor-sharp.
      Even very healthy clumps can die out in the center, in which case the dead center can be dug up and removed and the new outer growth replanted. Dividing the plants occasionally will reinforce vigor.
      Lauren Springer writes "Grasses require more artistic attention than the average run-of-the-mill new perennial introduction. Their uninhibited wildness, their linear silhouettes, their lack of blooms in the traditional sense all demand creative placement. A gardener needs to understand the unkempt look of nature, the subtleties of texture and form." She recommends planting them with "similarly natural, wild-looking companions."
      If gardening with grasses is new to you, here are some of the many ways they can be used to complement other plants in the garden:
♦Planting prairie dropseed with small narcissus or other bulbs and using grasses to cover the yellowing foliage of spring bulbs.
♦ To support delicate plants like mallow, pincushion flower and coreopsis which might otherwise fall over or fade mid-summer.
♦In combination with meadow plants like bee balm and coneflower with which they are often associated in the wild.
♦Mound-forming grasses look good with Mediterranean sub-shrubs like lavenders, salvias and Russian sage.
♦With members of the carrot family (sea holly and fennel) and other umbrella-shaped flowers like yarrow, sedum and Joe Pye weed -"Their habit is characteristically loose and naturalistic, often fine-textured and delicate, and hence perfectly at home amongst the grasses. Yet, their flowers are typically arranged into flat-topped umbels, which often strike up contrasting relationships with the leaves of nearby upright-growing grasses" (Gardening with Grasses).
♦Planting large-leaved plants in the foreground to anchor more delicate grasses in the distance.
♦Plants with stiff leaves-yucca, daylily, iris-provide a striking contrast to billowing grasses.
♦Grasses that hold up well against winter winds, snow and cold include eulaliagrass, switchgrass, Indiangrass and fountaingrass.
♦The buff color of winter grasses makes a good backdrop for the red skeletons of dogwoods, etc.
♦The pale, neutral colors of grasses in winter also contrast well with the dark skeletons of perennials like coneflower, sedum, etc.

Recommended Reading
Brookes, John. Natural Landscapes.
Darke, Rick. The Color Encyclopedia of Ornamental Grasses and Ornamental Grasses.
Greenlee, John. The Encyclopedia of Ornamental Grasses.
King, Michael and Piet Oudolf. Gardening with Grasses.
Steinegger, Don. Ornamental Grasses in Nebraska Landscapes (NebGuide G96-1310-A).