Water-Wise Landscape Design: Selecting Turf Options

Water-wise landscaping is not anti-turf, but about matching turf selection to the design needs and use of the site.   

With Colorado’s continued population growth, water use has become a critical issue. Water conservation helps reduce total water demand and reduce the extensive cost of expanding a community’s water infrastructure.  

In a typical community, water use more than doubles during the summer irrigation season. From a statewide perspective, landscape irrigation accounts for 7 to 10% of Colorado’s total water use. 

Benefits of Grass

Healthy grass is an aesthetic asset and a factor in property value. It provides a backdrop for other landscape elements pulling the landscape design together. 

The growing body of evidence points to the positive health and environmental contributions made by lawns and other grassy areas. A healthy, vigorous lawn with high plant density provides the following benefits: 

• Conversion of CO₂ to O₂ – Twenty-five square feet of actively growing grass produces enough oxygen for one person per day. On a global basis, grasslands of the northern hemisphere are second to the tropical rain forests in the CO₂ to O₂ conversion.   
• Pollution breakdown – Microorganisms found in the soil of actively growing turf, breakdown organic pollutants, including air contaminates, pollen, and pesticides. 
• Wind erosion – Grass cover prevents wind erosion of soil, trapping dust, and pollen. 
• Water quality – Turfgrass areas play a significant role in reducing surface water runoff, a key factor in non-point-source pollution in the landscape setting.
  • An average golf course of 150 acres can absorb 12 million gallons of water during a 3-inch rainfall. 
  • A thick turfgrass allows 15 times less runoff than does a lower quality lawn.
  • A healthy, dense stand of turfgrass can reduce runoff to almost zero.
  • Compared to a garden or field planted to row crops, grassy areas reduce soil erosion by 84 to 668 times.
  • To protect surface water quality, direct surface runoff onto grassy areas allowing for natural filtering in the biologically active turf soil. 
• Soil structure – Actively growing grass supports soil organism activity that improves soil structure.
• People space – Turf is basic “people space” with a cool, dirt-free activity space for children and adults. 
• Element of landscape design – Turf brings unity to a landscape design and provides a neutral background to set off flowers and shrubs. 
• Property values – Turf quality influences property appeal and marketability.
• Fire defense zone – Irrigated mowed lawns is an important aspect of fire management in communities.  Dry, unmoved grass/weeds become a major fire hazard. 

Turf Selection: Creating Practical Turf Areas

High input lawns are a habit in American and European landscapes since the days of King Louis of France.  However, does the property use require the perfect green lawn with high inputs or would a moderate quality lawn with reduced inputs or a low input lawn be acceptable for the site?   

Many lawn care problems arise from management differences between high, moderate and low input lawns.  For many gardeners, there is a conflict between expectations and inputs. Table 1 summarizes difference in high, moderate, and low input lawns. 

Table 1. Comparison of High, Moderate, and Low Input Lawns 

Grass and Water Use

Contrary to popular belief, there is no magic lawn type that delivers top quality with minimal inputs.  The quality of any turf is directly dependent on the amount of summer rainfall and supplemental irrigation it receives. A lawn’s tolerance or resistance to drought is a complex situation. A “drought tolerant” species may or may not use and/or require less water depending on many factors.  Factors contributing to drought tolerance include: 

• Species (including its actual  water use, rooting depth, and ability to go dormant) 
• Soil tilth and soil oxygen levels (rooting depth) 
• Wind and sun exposure (actual water use) 
• Mowing height (high mowing leads to deeper roots). 
• Traffic, (any lawn is intolerant of traffic when dry). 
• Salt levels in soil and irrigation water. 
• Previous irrigation pattern (frequency and watering depth).

The bottom line is that species selection is secondary to irrigation management in water savings.  A more drought tolerant lawn species will not use less water if managed like a high input lawn! Since Kentucky bluegrass, turf-type tall fescue, and Buffalograss make up 99% of home lawns in Colorado, this CMG GardenNotes only looks at these options.

Deeper Rooting Turf

If a turf is deeper rooting, it requires less frequent irrigation (i.e., stays greener longer between irrigations). However, it will also require a heavier/deeper irrigation to recharge the rooting zone, so actual water use is not necessarily reduced. Deeper rooting may or may not be an irrigation savings technique depending on the frequency of soaking summer rains and the irrigation pattern. If the area can depend on frequent soaking summer rains, the deeper rooting cultivars can be an advantage to keep the grass green between rain events. If the lawn is automatically watered two or three times a week, potential rooting depth is a moot point. [Figure 1]. Many gardeners mistakenly assume that deep rooting is a water savings because irrigation is needed less often. However, the frequency of irrigation is not the primary factor to consider. The issue is total water consumption.

Kentucky Bluegrass Makes a Great Lower-Input Turf Option

Kentucky bluegrass, KBG, is the standard for home lawns due to the rich blue-green color and its high tolerance for wear. Water use primarily depends on the gardener’s irrigation management. On a community wide basis, we use twice the amount of water that the KGB lawns actually need. Research studies show that the most gardeners actually do a good job of irrigation management. However, in any neighbourhood, some gardeners apply four to ten times the amount of actually needed by the lawn. 

With KBG, water use and growth actually slows when the soil begins to dry down. However, to capitalize on this dry down requires careful irrigation management rather than automatic irrigation on fixed days of the week. Irrigation demand varies significantly between cultivars. Some deeper rooting cultivars require less frequent irrigations. Some cultivars demand 25% less total water.  

KBG goes dormant with water stress during the hottest and driest part of summer. Summer dormant KBG is a standard in many parts of the eastern United States. Will summer dormant with green lawns in the spring and fall work for the site? It is not the KBG that demands the heavy irrigation but rather the gardener’s management style and a desire to maintain a green lawn through the summer rather than allowing the KBG lawn to go dormant. 

High input KBG makes a great “people space” for high use areas like a ball field with lots wear and tear.  Few home lawns have this high traffic situation demanding high inputs. Moderate input KBG (irrigated at 80% ET) fits the need for most home lawns where a beautiful green lawn is desired. When irrigated at 60% ET, KBG makes a thinner carpet. This may be well suited for lower use areas. Where summer dormancy is acceptable, KBG makes a great minimal input lawn. It needs to be greened up in the cooler weather of spring and fall with rainfall and supplemental irrigation. The public objection to summer dormant lawns is that so many are found in un-kept yards that become the neighborhood weed patch. 

Turf-Type Tall Fescue Makes A Great Lower Input Turf Option

Turf-type tall fescue may develop deeper roots than Kentucky bluegrass (KBG), depending on soil tilth (oxygen levels), cultivars, and irrigation patterns. This deeper rooting may allow longer intervals between irrigations, but it should not be mistaken for true water savings. Unlike KBG, tall fescue cannot slow its growth and water use as the soil dries, and its actual water use may be significantly higher. Tall fescue also cannot go dormant, requiring irrigation during summer dry spells. Based on evapotranspiration (ET), the water use of turf-quality tall fescue is only about 10% less than that of KBG. Irrigation management has a far greater impact on water savings than turf species selection. Switching from KBG to tall fescue alone will not save water. However, tall fescue can be an excellent reduced-input turfgrass for sites where top-quality turf is not critical to the landscape design.

Buffalograss Quality Is Dependent on the Amount of Summer Rain and Irrigation It Receives

Being a warm season grass, Buffalograss will be dormant brown from early fall (first frost) to late spring in Colorado. To be green in the summer, water use for Buffalograss is about 1 inch of rain and irrigation per week. To remain green in Colorado summers, Buffalograss generally requires irrigation to supplement natural rainfall. Turf-quality Buffalograss requires 50% less rain and irrigation per season than KBG. This reduction is due, in part, from being dormant in the spring and fall. 

Comparative Seasonal Water Requirement

Table 2. The comparative season water requirement (including summer rainfall and irrigation) of lawn options.

This publication, reference GardenNotes #412, is developed as part of the Colorado State University Extension Master Gardener Program.