Long, graceful, golden leaves swaying in the gentle breezes of late summer with iridescent seed heads nodding above vertical sheaves turning gold, bronze, or maroon as fall approaches. . .this is one of e the reasons gardeners include grasses within their plantings. Every gardener knows that ornamental grasses provide structure and a neutral backdrop for an array of blooming plants placed in front of them. They add fine texture, and can be planted in clump-forming masses which appear as mopheaded groundcovers, or they can be woven in and among taller perennials. Whether used in a perennial garden or meadow planting, the design reasons for planting grasses are often stated, but grass plants offer more than their aesthetic features; they have unseen benefits for the garden, as well. Grasses can actually help to improve and then stabilize your garden's ecosystem environment, that interwoven mix of soil, water, and air which can help or hinder plants.
Grasses Use Less Water and Conserve Soil
J. E. Weaver, a passionate investigator of prairie systems from 1916 to 1966, found that grasses make maximum use of rainfall and prevent soil erosion. Their root systems are vast networks of fibrous material which distribute rain. Weaver found that the vertical leaves receive and allow rain drops to spread over the ground surrounding the plant, where undecayed litter lies and "forms an intricate series of minute dams and terraces" which "hold water until it can percolate" into the soil. Then, the root system, an every-which-way conglomerate of fibers, further disperses the rainwater as it is received. Runoff is reduced. and the grass plant has made even hard rain more available to itself and to the plants near it. Where pounding cloudburst-like storms occur, this water holding device can make the difference between water used and water gullied away.
If your garden includes changes in elevation, placing grasses uphill of other plants can make water more available to them, while helping to hold soil in place. That fibrous root network, one which Weaver found can be longer than the top growth is high, stabilizes a slope. During the Great Drought of the 1930's, multitudinous acres of prairie sod which included a vast number of grass plants, was stripped to plant crops. For years afterwards, soil clouds rolled over the landscape, filling the air with particles, as there were no established root systems left to hold the soil in place.
Sun and Wind Screens
Gardeners admire the graceful leaves of grasses, swaying gently in the summer breeze. All the while, grasses are tempering the climate within your garden by acting as shade and wind screens, and by covering the soil's surface. An ornamental grass, particularly a taller one, filters sunlight, thereby offering a gentler, less scorching illumination to companion plants. Particularly in the harsh sun of the West, this screen can benefit plant partners, preventing leaf scorch or dehydration.
Where there's a sun screen, there's also wind protection. A vertical mass of grass foliage allows for air circulation, while cutting the severity of drying winds, and because each contains a large leaf surface area, grasses provide higher humidity at garden level, which is especially helpful in dry climates. Plants transpire, or give off moisture through their leaves and grasses have an abundance of them.
Soil Builders and Mulch
Think of the amount of soil a mature clump covers in your garden. Depending on its size, it will "mulch" from ten inches to five feet or more of your valuable topsoil, the soil which makes nutrients and water available to plants. Mulch can conserve surface moisture. A grass does that by shading. Additionally, grasses continually slough off leaf, stem, and root materials which slowly decay, providing a constant source of organic matter. The end result of its decomposition is dark-colored humus, which provides water holding capacity in fast-draining soil and improved drainage in tight clay.
Easy Garden Participants
Finally, ornamental grasses are easy to grow. They are highly pest, disease, and weather resistant, yet provide food and shelter for various forms of wildlife, including pollinators. The Xerces Society
recommends adding at least one species in a native planting as a nesting or overwintering site for certain butterflies and bees.
Grass plants are undemanding in terms of water, added nutrients, and human maintenance. Cut them down to their base in the spring, so that their new foliage looks fresh each season. Divide the clumps every few years, as older clumps die out in the center. Grasses require consistent water to remain green, but don't need more than rainfall, except in long, dry periods. And they provide their own nutrients, so added fertilizers aren't necessary.
Consider grasses to be not just ornamental, but essential to the ecosystem you're creating. A garden is more than a mere visual aesthetic, it is an interrelated system of water, air, soil, and organic beings, both plant and animal. Each addition changes the system somehow, improves it, adds to its complexity. Grasses enrich it, conserve it, and enliven it. They more than earn their keep.
Print Sources
Weaver, J.E. Prairie Plants and Their Environment. Lincoln, NE: University of Nebraska Press, 1968. Print.
Burns, Deborah, ed. The Xerces Society Guide: Attracting Native Pollinators. North Adams, MA: Storey Publishing, 2011. Print.
Kay Galvan - Kay Galvan has created residential and commercial gardens for twenty-one years on Colorado's high plains.
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