NCSU Floriculture Research
Ornamental grasses typify the "New American Garden", the term that is used to describe landscapes that resemble meadows full of native plants. This new way of thinking about landscapes is leading us away from regimented European-style borders and towards freer, more democratic forms. Many people credit the landscape architects Wolfgang Oehme and James van Sweden with popularizing this type of planting. In their landscapes, Oehme and Van Sweden seek to capture the spirit of the Great Plains, full of rolling hills and flowing grasses.
Ornamental grasses have increased in popularity due to other factors. They require very little maintenance, are quite drought tolerant, and have very few pests or diseases. Grasses add movement and sound, height and grace to gardens. In addition, there are many new, compact cultivars that can be used in small landscapes and in containers. Grasses are easy to propagate, they can grow in almost any soil and weather, and they need little fertilizer. As an example of the popularity of ornamental grasses, Calamagrostis x acutiflora ‘Karl Foerster’ was chosen as the Perennial Plant Association’s Perennial Plant of 2001 for its excellent performance over many years in Zones 4-9.
Grasses were easy to integrate into the upper Mid-West and Great Plains states, and the Mid-Atlantic has also experienced great success with grasses. The Southwest is interested in grasses because of their drought tolerance. Thanks to new research, the Southeast is now able to buy heat tolerant species that will perform in the high humidity and long, dry summers. Researchers at the University of Florida have been conducting studies to determine the best performers for the Florida Panhandle, focusing on plants grown in full sun and drought-like conditions. Some of their top-rated plants included Miscanthus sinensis ‘Zebrinus’ and ‘Arabesque’, Pennisetum alopecuroides, and Muhlenbergia capillaris. Poor performers included Calamagrostis arundinacea, Sesleria autumnalis, and Deschampsia caepitosa. In a study conducted at Texas A&M, researchers found that people preferred purple fountain grass (Pennisetum) and Lindheimer’s muhly (Muhlenbergia) to big bluestem (Andropogon). Please refer to our website, as we have links that recommend ornamental grass cultivars for almost every region of the country.
Table 1 focuses on the true grasses (those in the Poaceae family), but there are several other families of plants that are sold as ornamental grasses. These include the rushes (Juncus), sedges (Cyperus and Carex), sweet flag (Acorus), and New Zealand flax (Phormium).
Several reputable ornamental grass wholesalers have established themselves nationwide. These firms have developed their own marketing programs and provide cultural information to grower-retailers. Refer to our website for a list of ornamental grass suppliers.
Cool season grasses grow in spring and fall. Since they are dormant in summer, transplanting or dividing is not recommended at this time of year. In the landscape, cool season grasses often require more division and are not as drought tolerant as warm season grasses. Warm season grasses really put on growth in summer.
Grasses can also be divided between clump forming and rhizome (or stolon) forming. Clump forming grasses do just that. They are not invasive and grow by increasing their circumference every year, so the centers may begin to die out. Rhizome forming grasses are often called running grasses, and they can be invasive.
Division is the best way to propagate ornamental grasses. The best time to divide grasses is in the late fall or winter, after they are fully dormant. Each division should have at least three stems (culms). Divisions can be grown in cell packs or pots, but grasses grown in small containers can dry out very quickly. Divisions and liners, especially of large or aggressive grasses such as Miscanthus and Pancium, can also be potted direct to final containers (1 or 2 gallon pots). Incorporate a 6-month controlled-release fertilizer into the potting medium at planting. Late summer growth can cause potted grasses to become top-heavy. Consider Bonzi media drenches at rates of 1 and 2 ppm, as these have been shown to be effective at controlling the height of potted pampas grass. Although the production for most ornamental grasses is much longer than for annuals, vigorous grasses will develop into large, marketable plants after only 12 weeks of growth.
The key to creating grass sales is to offer only those plants that grow well in your region. Many consumers in the North were turned off when the big box stores sold purple fountain grass as a perennial rather than an annual. Almost every state has information on the adaptability of ornamental grasses for that region.
So many people are looking for low-maintenance plants and landscapes that it’s amazing that ornamental grasses aren’t overused. Promotion of grasses as durable, pest-resistant, low-water and drought-tolerant plants will be enough to sell anybody.
Retailers who are afraid that grasses won’t sell because "they don’t have any color" should look at purple fountain grass (Pennisetum), zebra grass (Miscanthus), and blooming muhly grass (Muhlenbergia). In the landscape, grasses look best when combined with other perennials. Mixing grasses into the perennials sales area will allow customers to see how well these two go together. Pay attention to color here: mix silvery blue grass foliage with white, blue and purple flowering perennials and annuals. In the heat of summer, nothing looks cooler than white, and a large variegated Arundo donax makes a powerful statement. Grasses also offer a soft, graceful form that is not common among annuals.
Rather than promoting the compact grasses as groundcovers, offer them as plants to control erosion. Weeping love grass (Eragrostis) is extremely effective and is often planted at new highway sites in the South for this purpose. The John Greenlee Collection of ornamental grasses, offered by Euro-American Propagators, focuses on compact species and cultivars grown especially for pot culture.
The big sales period is late summer and fall, when established grasses are blooming in the landscape. Unfortunately, potted grasses can look straggly during this time of year. How can a grower overcome this limitation? Use ornamental grasses in the display garden, and have excellent photos of the whole grass, inflorescence and all, so that the mature form can be seen.
Ornamental grasses will continue to increase in popularity. They are the herbaceous giants of the summer border. Coarse or fine, ornamental grasses offer texture to the heat-stricken annual bed and soften containers. Customers have begun to appreciate the versatility of grasses in their gardens and will continue to expand their collections. Be ready.
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