North Dakota State University * Dickinson Research Extension Center
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XERISCAPE ORNAMENTAL PERENNIAL GRASS TRIAL FOR LOW WATER USE LANDSCAPING

Llewellyn L. Manske, Range Scientist, NDSU, Dickinson Research Extension Center
Jerry C. Larson, Extension Agent, NDSU, Extension Service, Stark-Billings County

Western North America has an increasing problem of providing adequate quantities of clean water for domestic use. A large portion of western municipalities' water supply is used for watering lawns, gardens, and landscape plants. Traditional landscaping frequently selects Kentucky bluegrass lawns and ornamental plants that require large amounts of water to remain beautiful. Several agencies and institutions joined the Associated Landscape Contractors of Colorado and Denver Water in 1981 to develop the concept of "Xeriscape" gardening. Alternatives to the traditional techniques are being examined to develop landscapes that are harmonious with the local environmental conditions and use less water. Homeowners in western North Dakota have experienced the high costs of using domestic water for traditional landscape plants and have become aware of the need for alternative landscaping plants. Grass species in this trial are being tested and examined for use as plant material in low water use landscaping.

The purpose of Xeriscape gardening, or low water use landscaping, is to conserve expensive, precious domestic water by following seven simple commonsense principles.

• Use plants native to the region or plants adapted from areas with very similar environments and arrange the plants in zones with similar water, sun, and soil needs.
• Design the plants in arrangements that match family needs and lifestyle and select plants that provide color, texture, shade, and wind protection for all four seasons.
• Consider limitations of soil's water-holding characteristics and organic content and make improvements by amending the soil with composted plant material or aged manure.
• Limit turf grass lawns to areas actually used as "outdoor carpets" and select low water use grasses like blue grama, buffalo grass, crested wheatgrass, or tall fescue.
• Mulch with organic matter like wood or bark chips between plants to reduce evaporation and erosion and resist the use of plastic beneath decorator rock.
• Install water-wise irrigation systems and adjust them for maximum water savings with seasonal changes.
• Minimize maintenance to proper seasonal pruning and weed pulling and reduce fertilizer and pesticide applications.

Low water use landscaping achieves the desired goal of conserving water, money, leisure time, and precious resources while providing healthy, beautiful landscapes that add value to property. Xeriscape gardening combines landscaping with conservation.

Methods

This multi-year trial was designed to test and evaluate native grasses and adopted horticultural grasses as low water use ornamental landscape plants in western North Dakota. Thirteen native grasses and eleven horticultural domesticated grasses (Table 1) were included in this study. The research plots are located at the Dickinson Research Extension Center. These plots are managed with minimum maintenance, little supplemental irrigation water, no fertilizer, no herbicides after plot establishment, and hand rouging of weeds when necessary. The study consisted of three replications (Table 2). The grass plants were evaluated for vigor, ornamental value, seedhead aesthetics, color, and height. Vigor, ornamental value, and seedhead aesthetics were rated on a scale of 0-5 (Table 3). Color was recorded as one of twelve colors (Table 3). Total plant height was recorded as one of three height categories (Table 3). The twenty-four grass entries were randomly placed in plots in three replications (Table 4). Two evaluators rated each grass replication during early, mid, late, and post growing season periods. The statistical methods used to analyze differences between means was a standard paired plot t-test.

Results

Mean evaluation ratings of grass entries are shown in tables 5-7 for mid, late, and post growing season periods for 1998, respectively. The grass entries were not evaluated during the early growing season period of 1998 because that was the establishment period. Plants on replication plots of little bluestem, buffalo grass, Indiangrass, Canada wildrye, sweetgrass, and sand love grass died during the first year of the trial as a result of weakened condition caused by the plants being covered by wood chips for several days and not receiving additional attention to assist the plants recovery. These plants will need to be replaced in the spring of 1999. The mean values of the evaluation ratings of these six grass entries with dead replication plots were determined by two methods. The mean evaluation ratings were determined by including the ratings of the replications with dead plants, and means were determined by including the ratings from only the replications with live plants. Mean evaluation ratings for vigor and ornamental value, which were determined by two methods, are reported in tables 5-7. The seedhead aesthetics ratings also report two mean values. The first value includes data from replications not having seedheads, and the second value includes data from only the replications with seedheads present.

Most of the grass entries increased in vigor and ornamental value from mid to late season periods or remained at high or medium ratings. Vigor and ornamental value decreased for most grass entries from late to post growing season periods (Tables 5-7). Several grass entries, little bluestem, big bluestem, prairie cordgrass, sweetgrass, feather reed grass, ribbon grass, blue lyme grass, sand love grass, giant silver banner grass, zebra grass, red switchgrass, autumn red, altai wildrye, and blue fescue, had medium to high vigor and ornamental value ratings during the post growing season period (Table 7). Most of the grass entries tended to have high seedhead aesthetics value ratings during the period from head emergence to seed development stages (Tables 5-7). A few grass entries, blue grama, prairie sandreed, switchgrass, prairie cordgrass, sand love grass, giant silver banner grass, autumn red, and pampas grass had medium or high attractiveness of seedheads after reaching full maturity and during the post growing season period (Table 7).

Most of the grass entries had distinctive attractive shades of green color during the early, mid, and late growing season periods (Tables 5-6). Many of the grass entries completed senescence during the late and post growing season periods, displaying attractive shades of red, purple, or yellow before turning tan (Table 6-7).

The height categories for the grass entries (Table 8) were determined when the plants were mature and the seedheads had reached maximum height. Mature height of a plant is important when designing landscapes. The trial included three short grass, thirteen mid grass, and eight tall grass entries.

Discussion

This is the first year of a multi-year trial designed to test and evaluate grass entries for use as ornamental plants for low water use landscaping. Most of the grass entries show positive potential for use as low water use landscaping plants. A few grass entries, sand bluestem, Canada wildrye, zebra grass, altai wildrye, and green needlegrass had one or more sample periods with low ratings, but these grass entries should not be dismissed as landscape plants yet because one year of data is not an adequate basis for this determination, and these plants may improve. Some of the other grass entries may not maintain their moderate or high value ratings for the long run under these low maintenance and low supplemental water conditions.

Low water use landscaping, which uses native and/or adopted horticultural plants, is an important alternative to traditional landscaping, which uses plants that require large amounts of domestic water to remain beautiful. The results of this trial will assist homeowners to select ornamental perennial grass plants for use in their low water use landscaping.

Acknowledgment

The authors thank Ron Smith, NDSU Extension Horticulturist, Fargo, for providing plugs of horticultural adopted grass species plant material #13 to 20, for assisting with plot establishment, and for providing consultation during the development of this research project. We thank Craig Armstrong for providing plugs of horticultural adopted grass species plant material #22 and 23 and for providing advice on plot management. We thank USDA Plant Materials Center, Bismarck, for providing plugs of native species plant material # 1 to 12. We thank Mike Knutson, USDA Plant Materials Center, Bismarck, for selection, collection, and delivery of native species plant material plugs and for assisting with plot establishment. We thank Jon Stika, NRCS, Area Agronomist, Dickinson, for making arrangements for native species plant material and for assisting with plot establishment. We thank James Nelson, DREC Animal Scientist, Dickinson, for preliminary preparation of plot area and for providing and spreading wood chips.

Reference Literature

Barondeau, D., R. Smith, J. Larson, C. Miller, J. Dohrmann, T. Becker, R. Gaebe, B. Schmidt, J. Buckley, and L. Manske. 1997. Xeriscape plant selection. NDSU Extension Service. Fargo, ND. 22 min. Video tape.

Denver Botanic Gardens. No date. Water-smart gardening. Brochure. Denver Parks and Recreation Department. Denver, CO.

Denver Water. 1996. Xeriscape plant guide. American Water Works Association. Fulcrum Publishing. Denver, CO.

Denver Water. No date. Discover xeriscape. Pamphlet. Xeriscape Colorado Inc., Denver, CO.

Denver Water. No date. Efficient irrigation systems at work. Pamphlet. Office of Water Conservation, Denver, CO.

Hill, L. and N. Hill. 1995. Lawns, grasses and ground covers. Rodale Press, Emmaus, PA.

Plant Materials Center. 1997. Native grasses for prairie landscaping in the Northern Great Plains. Brochure. USDA Natural Resources Conservation Service. Bismarck, ND.

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