Ornamental Grasses for Water Conservation in the Landscape

Proper plant selection can reduce water use and protect water quality, and ornamental grasses are important part of the landscape professional's plant palette. Grasses add unique textures and patterns to the landscape, often year-round, with few fertilizer and pesticide applications. Once established, many grasses need little supplemental irrigation and can develop extensive root systems that allow them to withstand periods of drought.

Cool Season and Warm Season Grasses

Grasses can be roughly divided into two types based on the time of year they are most actively growing: cool season and warm season. Cool season grasses tend to perform best at temperatures between near freezing to 75 degrees Fahrenheit. They will be vibrantly green in spring, and put out flowers and seedheads in late spring to early summer. During the heat of the summer, cool season grasses may turn brown and be mistaken for dead, but once temperatures drop again in early fall, active growth will resume. Warm season grasses, conversely, are dormant all winter and begin to green up in late spring. They thrive in the hot, often dry conditions of midsummer, and will flower and go to seed in late summer to fall.

Ornamental Grass Establishment and Maintenance

Spring planting is appropriate for most ornamental grasses, although cool season grasses may also be planted in early fall. Specimen plantings are best established with container-grown or field-dug plants, while large area plantings and grassy groundcovers can be more economically planted with plugs or bareroot plants. Planting depth is as important with grasses as it is with other plant materials. The crown of the plant should sit just above the soil surface to avoid rotting (crown too low) or drying out (crown too high); mulching around grasses should also be done with care, as it can cause rotting if the mulch is pushed up against the crown. Grasses should be watered as needed during the establishment year, after which they may require little or no supplemental irrigation. Fertilizer is generally not necessary; it can actually be detrimental to grass plantings, making plant stems droopy and messy-looking, causing some grasses to become too aggressive, or causing surrounding plants to put on too much growth and crowd out less competitive grasses.

Grasses are fairly pest- and disease-free relative to other ornamentals. While deer tend to favor tender broadleaf plants over coarse grasses, voles and gophers can cause damage to grass root systems (Darke, 1999). Grasses may also be affected by rust diseases that appear as orange or brown patches on the leaves. Darke (1999) suggests that maintaining good air circulation around plants and sensible cultural practices can reduce or prevent rust; rust can also be controlled with wettable sulfur or fungicides.
Long-term maintenance of grasses includes little more than cutting back, generally in late winter or early spring at the first sign of new growth or in fall if dry stems present a fire hazard (Maynard, 2003), and dividing plants when they begin to get too large or their center dies out. Divisions from the outer edges of grass plants are most vigorous; they can be taken from cool season plants in late winter to early spring or late summer to mid fall, and from warm season plants in late spring into early summer.

Drought Tolerant Selections to Consider

If you are looking to expand your palette choice of drought tolerant grasses beyond the ubiquitous miscanthus varieties, look for some of the following from regional and mail-order suppliers. Some are undoubtedly easier to find in the trade right now than others, but the more landscapers ask for these, the more widely available they will become.

Cool Season Grasses

Warm Season Grasses

References

• Darke, R. 1999. The Color Encyclopedia of Ornamental Grasses. Timber Press, Portland, OR. 325 pp.
• Maynard, B. 2003. Ornamental Grasses. GreenShare Fact Sheet. University of Rhode Island, Kingston, RI.

Written by: Jennifer Kujawski
Revised: 09/2011