Kids and pets romp around on the lawn. Golfers trample over fairways. Football players run up and down fields. The sun beats down on the turf, and drought reduces the amount of water available to the root zones. This all takes a toll on the turf. But you can improve the health and appearance of that thin, worn-down grass.
What is renovation?
Renovating is seeding over an area that has, or had, existing grass to improve the appearance. Typically, renovation is ideal for situations in which you have damage or dieback on less than 50 percent of the turfgrass, and existing turf isn’t torn out completely. It offers an easy way to fill in bare spots, improve the density of turf, establish improved grass varieties and enhance color. It’s mostly used when a large area of turf is thin with damaged areas or bare patches, but not completely bare.
Renovation can be done in the spring to help revitalize existing cool-season grasses, such as Kentucky bluegrass or tall fescue, or fill in bare spots left over from winter. However, competition from summer annual weeds and stress make this timing more challenging. The ideal time for renovating lawns is in the fall.
Overseeding is a common practice in warm-season (bermudagrass, zoysiagrass, etc.) markets where turf goes dormant during winter months. For homeowners, this process allows them to have a nice green lawn all year round. For sports fields managers and golf course superintendents, it’s important to overseed to ensure both aesthetics and playability remain intact during winter months. People expect to go to a sporting event or golf course and see a lot of green — so overseeding is an important week of their year to keep customers happy and coming back for more.
Preparation is key
Because of the high costs often associated with overseeding, proper preparation is a very important part of any renovation or overseeding project. Prep work may include many steps: figuring out the right time to overseed, soil testing and correcting any problems you discover, aerating, mowing or scalping, improving sunlight to the area through foliage maintenance, and applying soil amendments.
Timing is crucial to successful seed germination. Planting too early or too late will lengthen the time it takes seeds to germinate, or may prevent them from germinating entirely. Exact timing varies based on several factors, including grass species, geography and overall site conditions.
In cool-season markets where renovation is the predominant practice, seeds germinate best when the air temperature ranges on average below 85 degrees Fahrenheit. Typical cut-off dates for cool-season lawn renovations across the transition zone are mid-October. (These temperatures are good baselines, but make sure you research your specific part of the country before starting. Cut-off dates will vary by region in accordance with local first frost dates.)
When overseeding in the fall, a good rule of thumb is to wait until overnight temperatures are consistently below 65 degrees Fahrenheit, and the existing bermudagrass growth slows and begins losing color.
In the spring, overseeding should be done early enough that seedlings have time to mature before the summer heat arrives.
Healthy plants start in the soil, so having healthy soil contributes to your success. Know what’s in your soil, and what needs to be in your soil. Soil type, pH level and nutrients in the soil play an important part in plant health and growth. Soil testing removes the guesswork when applying fertilizer, lime and other soil additives.
Soil that’s too acidic or alkaline can impact nutrient solubility and the plants’ uptake of nutrients, causing the plant to get too much or too few nutrients. A pH range of about six to seven typically promotes the best availability of plant nutrients.
Use a soil sampler or soil probe to gather samples. Once you have your soil sample, a lab can test it and provide the results and recommendations for amending the soil. Ask your local supplier if they offer soil-testing services through regionally based testing laboratories. Review your results, and follow the guidelines to address nutritional deficiencies to amend your soil for the healthiest turf. When it comes time to plant, you will want to apply a high-phosphorus starter fertilizer. Phosphorus is a vital component in seed germination, and having ample amounts during germination is critical. (For a common source such as 18-24-12, apply 1 lb. of phosphorus, or 4 lbs. of this fertilizer formulation, during planting.)
For the best results, you’ll need good seed-to-soil contact. Aeration and verticutting are two strategies to achieve seed-to-soil contact.
If your soil is compacted, aerate the soil. Aeration gives the seeds plenty of space to grow, and allows the seed-to-soil contact that is vital for successful overseeding/renovation.
For low thatch-producing grasses such as tall fescue, you can bypass the aeration in lieu of verticutting, or vertical mowing, the lawn prior to seeding. Verticutting helps remove thatch and dead leaves, and also creates a furrow in the soil for the new seed to settle.
When overseeding/renovating, existing turf can block the new seedlings from getting the proper sun needed to germinate. Lowering the mowing height increases the amount of light that can reach the soil floor, where seeds are ready to germinate.
For renovations, lower the mowing height (but not below 3 inches). For fall overseeding, set the mower blades as low as possible, as scalping the dormant bermudagrass is not a concern. Once you’ve mowed, rake the soil with a metal thatch rake to remove clippings, thatch and debris.
Aerating, mowing and verticutting allow seed a better opportunity to succeed with proper seed-to-soil contact. If possible, increase the amount of sunlight that the seeds can get by trimming back the trees and shrubs around the area to be seeded.
Once you’ve prepared the foundation, you’re ready to apply soil amendments to get on the fast track to healthy turf. Soil amendments such as AquaSmart PRO and Holganix help the soil improve physical characteristics, including its ability to hold water or retain nutrients.
Selecting the right seed
Once you’ve completed your preparation work, you’re ready to start overseeding.
Select the right seed for your regional climate. You’ll need a variety and species that will be compatible with the existing grass but will work with your new goals, whether that is improving the color, improving playability or just filling in thin spots.
Reading the seed analysis label will help you make the right choice in knowing what to expect as seed germinates.
Every bag of seed is legally required to feature a seed tag that must contain the following:
Varieties and kinds of seed in the bag
Pure seed: the percentage by weight of each variety
Germination rate: germination percentage by seed variety for the different seed varieties contained in the bag
Other crop seed: other seeds that comprise 5 percent or less of the bag
Inert matter: non-seed materials, including mulch or fertilizer
Weed seed: percentage of weed seed contained in the product
Noxious weed: number of noxious weed seeds contained per pound (regulated and may be restricted by state)
Lot number: production lot identification number
Test date: germination test date
Sell by date: sell by date, varies by state
The National Turfgrass Evaluation Program (NTEP) evaluates all the new and premiere cultivars for three to five years across several different U.S. geographies. Selecting a seed variety that is NTEP certified ensures it contains the newest and genetically premiere varieties, which have been proven to grow in the toughest conditions.
Steps for successful overseeding/renovation
You’ve prepped the turf area and selected the seed, so now it’s time to spread the seed. Apply seed at the recommended rates. Use a drop spreader or a broadcast/rotary spreader; if you’re seeding a smaller area, use a handheld spreader or simply use your hand if needed.
Recommended Renovation Seeding Rates for Tall Fescue
Commercial Sites/Lawns: 5-8 lbs. per 1,000 sq. ft.
Recommended Overseeding Rates for Perennial Ryegrass
Commercial Sites/Lawns: 8-15 lbs. per 1,000 sq. ft.
Fairways: 10-20 lbs. per 1,000 sq. ft.
Tees: 15-25 lbs. per 1,000 sq. ft.
Athletic Fields: 10-20 lbs. per 1,000 sq. ft.
Next, apply a starter fertilizer. This will bring nutrients essential to healthy growth to your seedlings. The three primary nutrients in the fertilizer — nitrogen, phosphorus and potassium — will help your grass get off to a great start with top growth, root growth and all-around color and health. When it comes time to plant, select a high-phosphorus starter fertilizer to apply. Phosphorus is a vital component in seed germination, and having ample amounts during germination is crucial.
Be sure to check with your local extension office to learn about any application requirements if you’re unsure of phosphorus fertilizer restrictions in your area.
Hold on! You’re not quite done yet. When you topdress the lawn, you can add organic matter to the soil to provide protection and additional moisture support to new seed establishment. You don’t need much topdressing to accomplish this—just 1/8-inch can provide the coverage you need. Application of a product like Profile’s Covergrow mulch pellet provides just the protection and moisture management needed during establishment.
Keep a consistent moisture level for seven to 10 days after seeding. This will involve many light waterings several times a day — for example, water three times a day for 10 minutes each time. If the soil dries out too much, the seeds could germinate and die immediately. After a few weeks, you can increase the lengths of waterings to encourage deeper root growth. (Just like regular turf maintenance, sunny, dry areas will need more water during seeding.)
Once you see adequate coverage and growth in the area, return to a regular watering schedule. Return to your regular mowing and maintenance schedule once your new grass has grown to a height of 1-½ inches.
Congratulations! You now have a newly renovated/overseeded lawn ready for the upcoming season.
Jennifer Klemmetson is public relations specialist at Ewing Irrigation and Landscape Supply, Phoenix, Ariz. For more information, visitewingirrigation.com