Lawn Care During Drought Conditions
By Dr. Karl Guillard
The University of Connecticut, 2002

Cool-season turfgrasses adapted to Connecticut climatic conditions have a built-in drought response mechanism – it’s called dormancy. Turfgrasses such as Kentucky bluegrass will shut down growth when moisture is limited to conserve water. By most appearances, the grass looks “dead”, but in many cases unless there is an extreme lack of moisture for a very long time or if the drought occurs on very sandy soils, the grass will “recover” and renew growth with the return of moisture. So, to say that most lawn grasses in Connecticut are not drought tolerant is false. They tolerate drought by going dormant. Unfortunately, most homeowners desire a green lawn throughout the entire growing season and become concerned when their turf begins to undergo dormancy during hot and dry periods.

What steps can one do to care for a lawn during a drought period? First is to understand the different response to drought from the various turfgrasses adapted to Connecticut conditions. Kentucky bluegrass and perennial ryegrass are the two most widely grown lawn grass species. Both require a fair amount of available moisture or will go dormant relatively quickly. On the other hand, the turf-type tall fescues and the fine leaf fescues – creeping red fescue, hard fescue, sheep fescue – will retain color and quality for a longer period under drought conditions than will Kentucky bluegrass and perennial ryegrass. Therefore, a lawn comprising more of the fescues will maintain turf quality with less water than the bluegrasses or ryegrasses. If water supply for a lawn is a yearly concern or becomes a yearly concern, it may be time to consider changing the species composition in the lawn by overseeding in the fescues or a complete lawn renovation and reseeding with a higher percentage of the fescues.

If one cannot or does not want to change the lawn composition from a predominance of Kentucky bluegrass and perennial ryegrass to a predominance of the fescues, then other care practices need to be implemented for drought conditions. If irrigation is available and water supply availability is not an issue, then water should be applied at heavy rates on an infrequent basis. The reasoning behind this recommendation is that heavy, infrequent waterings will penetrate deeply into the soil and encourage a deep root system. Grass roots will grow to the water, so the deeper the available water, the deeper the root system. Light, frequent waterings actually encourage the opposite – most of the root system will stay in the shallow depths of the soil profile. This will predispose the grass to greater water stress because the water in this shallow depth will be used up quickly by the grass and some water will be lost through evaporation. The grass will then become entirely dependent on this shallow water and will not be able to reach deeper soil water if the water supply is abruptly curtailed.

Often during drought conditions, lawn watering is prohibited. Grasses conditioned to frequent light waterings will suffer more so if irrigation is stopped than grasses not irrigated or irrigated infrequently because of differences in rooting system depths. If watering restrictions are all but certain, then it is probably best not to begin to irrigate at all and allow the turfgrasses to acclimate to the low water availabilities. This is called “pre-conditioning”. A number of research studies have shown that grasses that were pre-conditioned to water stress better withstood and recovered much more quickly from drought conditions than grasses that were abruptly cutoff from irrigation. Of course the lawn will go dormant and not be as aesthetic pleasing, but the grass will be healthier in the long run.

There are other cultural management practices recommended during drought conditions. During low water availability, one should always raise the cutting height of the mower. The basis for this recommendation stems from the fact that grass rooting depths are related to mower cutting height – the longer the grass, the deeper the roots; conversely, the shorter the grass, the shallower the roots. If a grass plant has a deeper root system, then it will be able to access deeper soil water and retain quality for a longer period than shorter cut grasses.

During drought conditions, fertilizer applications, especially with nitrogen, should be avoided. Most of the commercially available lawn fertilizers are in the form of salts and applying fertilizers during a drought can worsen the situation. Fertilizing with nitrogen fertilizers stimulate shoot growth at the expense of the roots. So prior to or during drought conditions, nitrogen fertilization rates should be reduced or avoided. On the other hand, there is some evidence to show that fertilization with potassium prior to drought conditions may increase root growth, thereby allowing the grass to reach deeper soil water. The form of potassium fertilizer is important because of the salt damage potential: potassium sulfate is preferred to potassium chloride because of its lower salt index value.

Lastly, there are compounds called “wetting agents” that can increase the amount of water that is available to the grass roots. These act by reducing surface tensions and allow for a better spread of water through the soil. These are generally sprayed onto the turf and watered in, or they can be applied through the irrigation system. Wetting agents are routinely used on golf courses and high-end athletic fields. For the general homeowner, however, wetting agents may not be a viable alternative because of costs and lack of equipment. But, professional lawncare services should be able to obtain and apply them correctly.

In summary, here are lawn care tips for drought conditions:

· Irrigate deeply and infrequently
· Apply wetting agents if possible
· Pre-condition grasses to drought stress before water restrictions abruptly curtail watering
· Avoid the application of fertilizers during a drought
· Apply potassium-based fertilizers prior to drought conditions
· Reduce the rates of nitrogen-based fertilizers prior to drought conditions
· Raise the mower cutting height