Article and photo by Ann Wright, UC Master Gardener of Nevada County
From The Curious Gardener, Winter 2019
Thinking of a soft jazz melody, the sight of grasses swaying in the breeze offers a sense of peace and calm as the seasons change. As tiny flowers on grass stems glow with late summer and fall color, these beautiful plants can “jazz up” a garden landscape. Grasses are not just for lawns. Ornamental grasses and grassy-type plants are useful in gardens as ground cover; they add texture and color to borders and perennial gardens with the benefit of providing food and shelter for birds and beneficial insects. Tall plants in the grass family can be grown to create privacy screens; some are suited to be used as fillers in otherwise bare, drab landscapes.
With hundreds of grassy-type plants from which to choose, a basic understanding may help home gardeners select grasses to accent gardens. Sedges, grasses and rushes are three families of grass-like plants, and out of the three families, ornamental grasses are known to have the showiest flowers. There is a little mnemonic that helps learn distinguishing characteristics between types of grassy plants: “sedges have edges, rushes are round, and grasses have knees that bend to the ground.” Sedges are plants that fall largely among the genus Carex. Many sedges have a sort of triangular or 3-edged stem toward the flower, hence the term “edges.” Rushes on the other hand have pithy, round stems without joints. Rushes are perennial and fall in the genus Juncus. Grasses consist of thousands of plants world-wide that are distinguished by hollow, round stems with knobby joints or “knees” along the stem. The California Native Plant Society reports that about 80% of California’s native grasses are perennial, the rest are annual.
Grasses are further characterized as cool-season or warm-season plants. Cool season grasses flower in the spring and may be found in California’s central valley, the foothills and higher mountain meadows. These types of grasses thrive during the fall and early spring and may be green year round in some climates unless the temperatures fall consistently below freezing. Some examples of cool season grasses include Elymus glaucus (Blue wild rye), Danthonia californica (California oatgrass) and Melica californica (California melic grass). Calamagrostis (Reed grasses), Festuca (Fescue) and Stipa pulchra (Purple needlegrass) are other examples of cool season grasses. Warm-season grasses perform best in climates where summers are hot and dry with mild winters. During the winter when soil temperatures fall below 50˚-55˚ F, warm season grasses may go dormant and lose their green color. A common native warm-season perennial bunch grass is Muhlenbergia rigens (Deer grass). Other examples include Miscanthus, Molinia, Panicum and Pennisetum species. Warm season grasses can be planted in fall in our climate, before the plant goes into winter dormancy. The lovely fall foliage and dried flower stems may continue to accent the garden into the winter months.
The flowering part or inflorescence of the grass adds color, shape and striking focal points amidst other plants. Grasses have showy, shimmery plumes, bottlebrush-like spikes, and silky sort of hair-like flowers which add to the beauty of the garden. Some grasses also grow to a significant height which must be taken into consideration when selecting plants—identify how big the plant will grow so it won’t block other plants or irritate the neighbors.
There are up to 10,000 species of grasses in the world—the California Native Grasslands Association indicates that over 300 species of grasses are found in California, representing about 40% of California’s total native plant species. Many of these species are endangered. The decline in native grasses and grasslands is attributed to intensive cultivation, over grazing and introduction of nonnative species which choke out native plants. The Plant Right website lists three grasses considered invasive and potentially harmful to the garden environment which should be avoided: Pennisetum setaceum (Green fountain grass), Stipa/Nassella tenuissima (Mexican feather grass), and Cortaderia selloana (pampas grass).
To learn more about ornamental and native grasses and perhaps find a favorite to jazz up your gardens, look at the references accompanying this article, or perhaps take a trip to the UC Davis Arboretum where a number of native and ornamental grasses can be seen planted along pathways. The “Arboretum All-Stars” are selected plants that have been field tested and considered to grow well in our area (depending of course on elevation). The warm season grasses that made the cut are Stipa gigantea (Giant feather grass), Miscanthus sinensis (Japanese silver grass), and Muhlenbergia rigens (Deer grass). The cool season All-stars are Bouteloua gracilis (Blue grama grass), Festuca californica (California fescue), and Calamagrostis x acutiflora ‘Karl Foerster’ (Feather reed grass).
Once established, ornamental grasses grow with fairly little maintenance. Grasses that brown up during the summer may be cut back in the fall; others may be left until February or March as the tall seed heads add interest and beauty during the winter. Clump grasses can be secured with a piece of twine and cut below the twine or tape with well-sharpened shears.
Consider the enjoyment ornamental grasses may bring to your gardens and, as Roger Grounds reflects,“what is magical about grasses is their intimacy with the natural world—the way they reflect every mood, catching the sunlight in their flowers and seedheads… changing with the passing hours, ebbing and flowing with the seasons.”
References:
Greenlee, John. The American Meadow Garden. Timber Press. 2009.
Grounds, Roger. The Plant Finder’s Guide to Ornamental Grasses. Timber Press. 2002.
Harlow, Nora, K. Jakob. Wild Lilies, Irises and Grasses. University of California Press. 2003.
Hightower, Steve. Pruning Ornamental Grasses. http://sonomamg.ucanr.edu/2010_Feature_Articles/Pruning_Ornamental_Grasses/
Torr, Eddie. Grasses and Sedges and Rushes, Oh My!