MSU Extension

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Now is the optimal time to look at reseeding or sodding any turfgrass areas lost to the heat, humidity and disease that sporadically plagued turfgrass managers this summer. Daytime high temperatures have started to dip and hopefully the pattern of recent rainfall will continue in the coming weeks to aid any new establishment projects. This article will focus on tips for renovating/reseeding damaged turf areas. Future Landscape Alert articles will focus on fall turfgrass management practices to ensure a successful 2007 including core aeration, broadleaf weed control and fall fertilization (we’ll touch on fall fertility in this issue).

Reseeding damaged areas

The first decision you need to make is whether to spot seed the bare areas or if the whole area needs to be reseeded. This decision is basically one of practicality. Many turf areas made it through this summer relatively unscathed and turf death tended to be scattered. If the turf was simply thinned or there are small patches of dead grass, a fall fertilizer application and favorable weather conditions should facilitate the existing turfgrass stand to recover and fill in those bare spots. If the damaged areas are large, for example lawns that essentially have only sporadic green turf plants, then overseeding is going to be necessary to restore the area to turf.

Tools to renovate

There are a number of different methods to ensure that reseeding efforts are successful. First and foremost, you must ensure you get good seed to soil contact, ie. seed sitting on top of the soil or simply broadcast spread onto the turf without creating any holes or slits will not be successful. There are several options for creating the holes/slits to ensure seed to soil contact. Machines such as core aerifiers, power rakes, slit seeders or even hand raking small areas should get the job done. For established areas that may just need a light overseeding to improve density, a core aerifier is a viable option. It’ll also give you the benefit of improving soil aeration, which is critical for many sites that have compacted soils or high clay content. For areas that need lots of help, I really like slit seeders; these machines operate by creating a slice in the soil that the seed falls directly into and ensures the seed gets to where it needs to be. Many lawn care companies offer this service, or if you’re a do it yourselfer, these devices can usually be rented at the local hardware or rental store.

Species, seeding depth and rates

Making sure you have the correct species and cultivar, especially if you are overseeding an existing lawn, is a critical step to ensure satisfaction. One common frustration many property owners have after overseeding is that the newly seeded turf has a drastically different color/appearance than the existing turf stand. To avoid this problem I would suggest you do your homework to try and find out if you know the specific species and cultivar that was originally established. In most areas, if you’re not sure of the turfgrass species on the lawn, odds are its Kentucky bluegrass. Therefore, obviously you should select Kentucky bluegrass cultivars to reseed the turf. If, however, you are completely renovating an area and are looking for something a little different that might be able to withstand drought conditions better, I would give tall fescue a try. Look for catch words such as “Turf type” or “Improved” when selecting tall fescue cultivars. I would avoid the standard Kentucky 31 (K-31) tall fescue. It has its use in minimal maintenance landscapes or parks, but in most lawns it would look ugly due to its wide leaf blade. Turf type tall fescue is now being mixed with Kentucky bluegrass and is becoming more widely available to consumers, this might be a good option for folks who want to experiment a little and see what they think.

Please see our fact sheet on Purchasing Quality Turfgrass Seed: Read the Label at www.turf.msu.edu under the homeowner section for more tips on purchasing seed. Overseeding rates for Kentucky bluegrass are 1.5-2 lbs./1000 sq. ft. For mixtures containing perennial ryegrass or fine fescues, rates should be increased to 3-5 lbs./1000 sq. ft. For tall fescue the seeding, not overseeding, rate is 6-8 lbs./1000 sq. ft. Strive to incorporate the seed to a depth of about ¼ inch. Deeper planting depths may result in some of the seed not making it to the surface.

Consider mulch for moisture retention

Spreading a light mulch cover on top of the newly seeded area will help the soil retain moisture and keep the seedlings from drying out. The recommended rate for using straw mulch is 1 bale of straw/1000 sq. ft.. Be careful with how much mulch you apply, you don’t want to end up smothering those young seedlings. Apply enough so you can still see about 1/3 to ½ of the soil underneath. There are also numerous, more sophisticated mulch products that are easier to spread than straw and expand with moisture to cover the soil. Even something as simple as turf clippings can be used as mulch; once again, don’t spread them too thick over the area.

Fertilizer, irrigation and herbicides

At the time of seeding, apply a starter fertilizer at a rate of 1 lb. N/1000 sq. ft. to help those young seedlings get established. Make sure to keep the seeded area moist throughout establishment. In many cases, this may require watering several times a day. A good mulch cover will help the area stay moist so the site may be watered less frequently. Water lightly when irrigating – there is no need to see water puddling or running off the site.

To be safe, avoid applying all herbicides this fall, i.e. no weed and feed products. Young seedlings don’t tolerate herbicides very well and the guideline is usually to wait three "real" mowings before applying any herbicides or in some cases at least 60 days. By "real" mowings, I mean you’re actually cutting significant grass, not just running over the area to trim down any weeds.

Finally, don’t be afraid to get out there and mow the area. It’s always challenging to set absolute guidelines when talking about when you should start mowing new seedings. My recommendation, don’t wait until the seedlings are so tall they’re starting to fall over. If you typically mow your lawn at 3 inches – start mowing the newly established areas when the seedlings get to or slightly exceed the 3 inch height. Mowing turf helps it spread laterally and fill the area, so start those engines as soon as you start to see the grass creep up to your established cutting height. Hopefully, these tips will help you reclaim those bare areas and get the turf off the blocks quickly this spring.