This year there were multiple causes for turf decline in home lawns. High temperatures and drought were the primary causes for a decline in turf and an increase in weed incidence. During warm weather (especially temperatures > 87 °F) cool-season grasses like Kentucky bluegrass have trouble making energy while much energy is needed to maintain plant functions. In short, cool-season grasses don’t make energy well when it is hot out and as a result they don’t grow (roots or shoots) well in hot weather which can lead to a decline in turf quality. Water is also critical to the growth of turf. Water is a key part of photosynthesis and respiration reactions as well as many other plant metabolic activities. Turfgrass leaves and shoots are comprised of about 80% water. The recent lack of rainfall in parts of Indiana has led to a decrease in growth or summer dormancy (drought).
Some grasses such as Kentucky bluegrass enter a summer dormancy when soils begin to dry. Summer dormancy is a process where the plant stops growth and turns brown (dormant) but it is not dead. When rainfall returns following drought, Kentucky bluegrass will emerge from summer dormancy and resume normal growth. Even if drought tolerant species are utilized, turfgrasses can experience drought injury in the summer, especially where irrigation is not available, on southern slopes, and on shallow or compacted soils.
Drought Facts
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Though turfgrasses perform best with enough regular irrigation during the summer to keep them green and growing, they are very capable of surviving without rain or irrigation.
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Turfgrasses perform much better under slightly dry conditions than under wet or saturated conditions.
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Turfgrass dormancy (brown turf) is a survival mechanisms allowing survival up to up to 5-8 weeks without irrigation/precipitation without significant thinning upon recovery from dormancy. This would be under ideal conditions of no regular traffic, good soil, moderate temperatures, no shade, minimum thatch, etc. However, survival is affected by species, age, shade, fertilization, mowing, traffic, heat, etc., etc.; so optimum survival may not occur on your particular area.
Many homeowners in central and southern Indiana are trying to figure out how best to cope with the current drought because it is affecting their normal 1) fall seeding, 2) fertilization, 3) and weed control. Below are some strategies on how to cope with the current situation. The maps below show illustrate the lack of rainfall in central and southern Indiana over the past 90 days (since the heavy spring rains).
Managing turf during drought
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When possible stay off the turf! Limit traffic (including mowing) to minimize crushing of the turfgrass leaves and crowns.
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Water once every 4 weeks with ¼ to ½ inch of water to keep turf plant crowns hydrated. This amount of water should not green up the turf, but it will increase its long-term survival.
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Turf should recover in 1-2 weeks after significant rainfall returns.
Should I fertilize right now?
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Wait to fertilize until after the turf greens-up after the next rainfall.
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Normally we would recommend fertilizing 1.0 lb N/1000 ft2 in September and November in lawns. This year it may be necessary to fertilize in October and November to encourage recovery from drought prior to winter. Weak turf that enters winter dormancy will emerge in the spring weak and be more susceptible to weed invasion next year.
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Although aggressive fall fertilization is needed to help our turf recover, it could also promote some increased snow mold damage in turf next spring.
Should I apply a herbicide right now?
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Herbicides are ineffective on drought-stressed weeds and can be damaging on drought-stressed turf.
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It is better to hold off on applying fall broadleaf herbicides until rain returns and the turf and weeds being growing again.
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Broadleaf herbicides can be applied in Indiana until early November and still provide effective control.
Should I seed right now?
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It is not too late to seed, but it is past the optimum window due to the fact that we will start experiencing cooler weather soon which will slow down the growth of turf and thus take longer for seeded areas to establish and fill-in.
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Thin areas with 4 inch or smaller gaps in turf can be overcome with aggressive fall fertilization. Lawns with larger gaps in turf should be reseeded.
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Droughty, unirrigated areas can be reseeded now and they will establish once consistent rains return. Alternatively, droughty areas can be reseeded now and irrigated at least twice daily.
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Most herbicides require that newly seeded turf be mown 1-2 times prior to a herbicide application. Please read the specific herbicide label for the product you are considering using to learn more about seeding restrictions.
For more information about recovering your lawn from drought see the following publications
Rejuvenating Drought Areas after the Drought of 2002
Lawn Improvement Programs