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Is It time to Renovate Your Turf?

By North Carolina State University's A. H. Bruneau, Crop Science Extension Specialist (Turf), Fred Yelverton, Crop Science Extension Specialist (Weed Management), L.T. Lucas, Plant Pathology Extension Specialist, Rick L. Brandenburg, Extension Entomology Specialist

When thatch becomes too thick, new grass roots will grow within the thatch instead of reaching deeper into the soil, resulting in turf that is less resistant to stress. It's a good idea to cut a series of core samples like the one shown, to determine if your customers need to dethatch their turfgrass.

Lawn renovation refers to any procedure beyond normal maintenance required to upgrade an existing lawn. Renovation generally takes place on a small scale in isolated areas of the lawn. Bare spots larger than 4 inches in diameter should be replanted. Deterioration of the entire lawn may require re-establishment.

A deteriorated lawn is often a symptom of some underlying problem. Some of the major causes of lawn deterioration include: planting a grass that is poorly adapted to the site; overwatering, overfertilizating, mowing too low; poor drainage, heavy shade, compacted soil; improper nutrient balance or low pH; excessive thatch buildup. Before renovating, identify and correct the problems that may have caused the deterioration. Otherwise, renovation will be an ongoing process.

Soil Preparation

To achieve good germination and fast establishment, remove weeds and prepare the soil before overseeding. Do a soil test in the area to be renovated, and follow recommendations for nutrients and pH. If total renovation of an area is needed because of severe damage or takeover by weeds, cover the area with a black plastic sheet for seven to 10 days to kill most plants, including weeds. Those not killed will have to be manually removed as they appear. In bare areas, loosen the top 4 to 6 inches of the soil with a rake, hoe, shovel or roto-tiller. Fill in low areas and smooth the surface so clods are smaller than marbles. If the area is to be reseeded, add compost before tilling to enhance water retention and speed germination. It is also possible to renovate small areas by coring and reseeding.

Apply a complete (N-P-K) fertilizer to the soil. In small areas, hand application is acceptable. In larger areas, use a rotary or drop-type spreader to insure uniform distribution.

To insure uniform coverage of seed, use a rotary or drop-type spreader, applying half of the seed in one direction and the other half at a right angle to the first pass. Keep the overseeded areas moist by sprinkling lightly several times a day. As seedlings grow, water less often, but more deeply, to promote deep rooting.


Late summer to early fall is the best time to renovate cool-season lawns. Seedlings can survive the heat and drought stresses of summer better if they can establish themselves the previous fall and winter.

When thatch becomes too thick, new grass roots will grow within the thatch instead of reaching deeper into the soil, resulting in turf that is less resistant to stress. It's a good idea to cut a series of core samples like the one shown, to determine if your customers need to dethatch their turfgrass.


Seeding is recommended for grasses with bunch-type or slowly spreading growth habits. These include tall fescue, Kentucky bluegrass, ryegrass, bahiagrass, and fine fescue. To insure uniform coverage, use a rotary or drop-type spreader, applying half of the seed in one direction and the other half at a right angle to the first pass. Incorporate seed into the top one-eighth inch of the soil by lightly pulling a leaf rake over loosened soil or by running a vertical slicer over areas that have been aerified by coring. Adding a light covering of weed-free straw will help to protect the seeds from wind and also help retain heat and moisture.

Plugging can be used for those grasses such as bermudagrass, zoysiagrass and centipedegrass that spread laterally. Place plugs on either 6-inch or 12-inch centers, depending on the desired establishment speed. Use a plugging device to remove plugs of soil from bare areas and switch them with plugs collected from healthy areas.

Broadcasting large areas (15,000 square feet or more) is often reserved for bermudagrass. Rototill the recommended amount of fertilizer and lime as indicated by soil test results. Spread sprigs over the surface using specific rates. Press the sprigs into the top 0.5 to 1 inch of soil. Roll the area to firm the soil and insure good sprig-to-soil contact.

Care After Planting

Keep renovated areas moist with light sprinklings several times a day. As the seedlings, plugs or sprigs grow, decrease the frequency of waterings while increasing the duration to promote deep rooting. After the third mowing, water to a depth of 6 inches.

Mow the areas as you normally would, using a sharp blade. Keep weeds pulled or cut short until desirable grasses have germinated and the desired mowing height is achieved. This will reduce the competition for new seedlings. To enhance establishment, fertilize the new seedlings of cool-season grasses. A complete (N-P-K) fertilizer that provides about 1 pound of nitrogen per 1,000 square feet should be applied approximately 3 weeks after seedlings emerge. An organic fertilizer, which will release nitrogen and other nutrients more slowly, needs to be applied at time of planting.

Core aerification--the process of removing plugs of soil from turf--is an effective method of controlling thatch when combined with judicious fertilizing and watering.

Overseeding Warm-Season Grasses

In warm-season (usually bermudagrass) lawns, overseeding with annual or perennial ryegrass will help to maintain a green color and protect the dormant warm-season turfgrass during the cooler months. Occasionally zoysiagrass and centipedegrass are also overseeded. It is important that the warm-season lawn be lush and healthy before overseeding so that it can withstand the rather harsh cultural practices and competition from cool-season turfgrass associated with overseeding.

When to Overseed

Overseeding should take place in late fall, 2 or 3 weeks before the expected first frost or when the soil temperature drops below 75 degrees F. In the piedmont area, this is usually September 15 through October 1. Plan on 1 to 2 weeks earlier in the western part of North Carolina and 1 to 2 weeks later in the eastern part of the state.

The transition back to warm-season turf will begin in the spring when night air temperatures begin to reach 60 degrees F, and the warm-season grass begins to break dormancy. Regular maintenance practices for the warm-season grass, competition from the warm-season grass, warm temperatures, and disease should eventually force the overseeded species out of the lawn in the spring. However, overseeding for several consecutive years may result in gradual decline of the warm-season lawn and increase in the cool-season species. Therefore, it is important to establish a healthy warm-season lawn before considering overseeding.

This graphic gives you examples of problems you may encounter with your turfgrass along with some renovation solutions.

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o Prepare for overseeding by closely mowing the warm-season grass.

o Thin the turf, especially hybrid bermudagrass, with a power rake to improve seed placement near the soil. Centipedegrass and zoysiagrass are slow to recover from injury, so only lightly rake the surface on these lawns. Remove the clippings and raised thatch.

o Apply a complete format fertilizer with a N-P-K ratio of 1-2-2 based on 0.25 pounds of nitrogen per 1,000 square feet. Do not stimulate continued growth of the warmseason grass by applying too much fertilizer or applying fertilizer too early. Use a rotary or drop-type spreader to insure uniform application.

o Choose a seed species. Annual and perennial ryegrasses are the major overseeding species. They are both quick to establish and relatively inexpensive. Newer varieties of perennial ryegrass are more heat- and diseasetolerant and may be more difficult to remove in the spring than annual ryegrass or older varieties of perennial ryegrass.

o Use a rotary or drop spreader to apply the seed at 5 to 10 pounds per 1,000 square feet. Higher rates will produce denser and lusher lawns, but will leave more plants to remove in the spring.

o Topdress the lawn with a light layer of sand or compost to improve seed-to-soil contact.

o Water two to three times daily until the seedlings begin to emerge. Apply enough water to moisten the surface, but not enough to cause movement of the seed. As the seedlings emerge, water only once per day. Once the seedlings are established, water only when necessary to supplement rainfall.

o Fertilize every 4 to 6 weeks with 0.5 pounds of nitrogen.

o In the spring, when night air temperatures are regularly above 60 degrees F, mow the overseeded grass closely (1 to 1.5 inches) to reduce competition and promote growth of the warm-season grass.

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May 26, 2019, 3:10 pm PDT

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