Barbara J. Bromley, Mercer County Horticulturist 04
Many homeowners follow approximately the same maintenance program each year for their lawns. Some use multi-step programs. Some hire a lawn service company that makes between three and seven fertilizer, lime, and/or pesticide applications through the season. Some homeowners fertilize their lawns once or twice per season and use few or no pesticides to sustain their turf. Some have irrigation systems, some drag hoses, and some don’t water at all. A serious drought, especially one that starts without warning, will throw a monkey wrench into the workings of most of these programs.Regulations that affect who can water and what can be watered are put out by the New Jersey Department of Environmental Protection. It is not known when a drought will end or what the severity of restrictions will be. Homeowners that maintain their own lawns should consider the “minimalist approach” in years when drought restrictions are in place. (See cultural practices below.)
Grasses, like other plants, require sun, soil, and water to grow. Grasses differ in their individual requirements for sun or tolerance for shade, in the amount of fertilizer needed, and in the amount of water needed to prevent the grass from going dormant. Most turf grown in New Jersey contains cool-season grasses: Kentucky bluegrass, turf-type tall fescue, perennial ryegrass and fine fescues (hard, Chewings, and creeping red). Each of these grasses tolerates the conditions of a dangerously dry year differently.All grasses go dormant eventually if water is withheld. Dormancy is a condition under which the grass blades turn gray green, then tan. The blade dies, but the crown and root system remain alive. When proper growing conditions resume, the plant grows again and new blades are sent up from the crown. Grass plants may die eventually if the drought is too long, if the grass is marginally healthy to start with (poor growing conditions or cultural practices), or if the grass is a perennial rye or other drought- intolerant type.
Following are some of the CULTURAL PRACTICES that will help turf to survive a serious drought:
- Grasses: Most grasses are not drought-tolerant until they have formed a strong root system and are established which usually takes about one year from seeding or several months from sodding. Some of the grasses in the lawn mix should be drought-tolerant types such as tall fescue or the fine fescues that go dormant slowly. Established bluegrass will go dormant fairly quickly if water is withheld. Perennial ryegrass is not drought-tolerant. In any event using the right grasses should be planned for before drought restrictions are applied or drought even becomes an issue.
- Reseeding: Sometime there are bare spots in turf that need to be reseeded. Although late summer is the best time, in most years reseeding can also be done in spring. In a very dry late winter or spring when water availability is questionable, overseeding should wait until late summer. Grasses need water to establish initially and the seed and time will be wasted if the seeded areas can’t be irrigated.
If seeding is done in the spring of a drought year, the seed may remain dormant until moisture breaks dormancy. If rains or irrigation continue the grass will grow, develop healthy roots, and thrive. However, in drought years this is usually not the case. The grass germinates, then dies from lack of water.
- Soil test: In any year have a soil test run to determine pH, phosphorus and potassium levels. Bring the soil pH to 6.0-6.5 and maintain optimum levels of nutrients to keep the grass healthier. Optimum potassium levels are especially important for environmental and drought stress tolerance.
- Liming: Apply limestone to bring the pH into the desirable range and stimulate proper root development. Limestone can be applied at any time in the spring or fall, but takes several months to affect a pH change.
- Fertilizing: In a normal year or when irrigation is allowed, properly applied fertilizers will be put in solution and be absorbed by the grass roots to stimulate growth. In a very dry spring when irrigation is not allowed, fertilizer applications should be reduced to a minimum for the grass grown, which may mean not fertilizing at all. Grasses that are lush are not as drought-tolerant and are more disease prone. On the other hand, grasses that are starving are not tolerant of serious stress either. Except on irrigated turf where grass clippings are removed, never fertilize cool season grass lawns in summer.
- Mowing: A sharp mower blade, leaving clippings, removing only 1/3 of the grass blade at each mowing, and raising the mowing height as weather warms is important in any year. In a drought year raise the mowing height to 3 or 3 ½ inches at the beginning of the season instead of waiting for hot weather. In summer raise the mower to at least 4 inches if the grass is still growing. Leave the clippings. When the grass is completely dormant stop mowing until growth resumes.
- Watering: In any year grasses do not need much additional water to survive. Water is only necessary to prevent dormancy; so many people use irrigation systems or drag sprinklers around to apply water just to keep lawns green. One to 1 ½” should maintain a green turf.
In a serious drought year watering of established residential and utility turf is not allowed at all. When watering is allowed some people water every time it is allowed, perhaps every other day. Don’t be lured to this. If total restrictions are imposed, these shallow-rooted grasses will not be able to survive the abrupt removal of water that comes with tight restrictions.
For healthy lawns of drought-tolerant grasses, water is not necessary. Dormant grasses will recover with fall rains. Lawns that have a shallow root system from excessive watering, shallow soil, improper pH or nutrient levels, or any other condition not conducive to root development will probably languish and die in drought years. These lawns will need to be reseeded or sodded in late August or early September.
Lawns that are allowed to go dormant naturally can usually tolerate a month or more of no rain or irrigation. The blades turn brown or tan, but the crown remains alive. Longer periods of drought than a month or so may cause grass plants to die, because the crown and roots will dry out completely. If possible, try to irrigate ¼” of water at least once after four or five weeks to rehydrate the crown. This amount of water will not bring the grass out of dormancy, but will keep the crown alive.
- Thatch: If a lawn has a ½ inch layer of thatch (dead roots and stems), leave it. This layer will help cushion drought-stressed crowns against breakage. Thatch layers greater than ¾ inch in a drought year should be removed when growing conditions improve.
- Reduce amount of grass: Add mulched areas by enlarging beds and reducing the amount of grass under trees. Less grass under trees will reduce the competition for available water by grass roots so the trees will not go into stress as quickly.
- Herbicide applications: Preemergence crabgrass control could help prevent the heat- and drought-tolerant crabgrass from taking over a thin lawn during stress conditions. These products are usually applied in combination with fertilizer.
In normally moist years many people apply a weed-and-feed product to kill broadleaf weeds. In a dry year consider applying broadleaf weed killers as a spot treatment on individual weeds. Do not use a fertilizer/weed killer combination product if fertilizer with pre-emergence crabgrass control has already been applied.
- Insecticide applications: A lawn under drought stress is less attractive to surface feeding (sod webworm, chinch bugs, cutworms) and root feeding (grubs) insects, but is also more severely damaged if an infestation occurs. (In wet years a naturally occurring fungus, Beauvaria bassaniana, will kill chinch bugs). Often damage from insects is not discovered until a lawn does not recover from drought (green up) when rains return. Monitoring for insect activity and applying an appropriate control can prevent damage during dormancy.
- General Pesticide Recommendations:
- Try not to make any chemical applications if the lawn is under heat or drought stress.
- Do not make pesticide applications if water is needed to activate the product, it will not rain, and irrigation is not allowed.
- Do not apply pesticides (includes insecticides, fungicides, herbicides) if the temperature is higher than 85ºF.
- Follow label directions when applying pesticides. Water is necessary to activate granular materials. Check local regulations for watering restrictions.
- Activity: If a lawn is dormant stay off it as much as possible. Recreation and foot traffic will wear down the crown of drought stressed turf. Dog urine will cause lawn death by ammonia burning of grasses.
If all else fails and the lawn dies in a serious drought year, have it reseeded in late August or September. Sod can be laid at that time or postponed until it is possible to moisten the ground prior to laying the sod and watering is allowed or rainfall is predicted.
|2002 Drought Web Sites, among others:
NJ Department of Environmental Protection – Drought web page
Rutgers Cooperative Extension – Drought web page