Six steps to fall turfgrass establishment
The cooler temperatures of autumn make it the ideal time to seed a lawn or reestablish dead areas following a stressful summer.
After another stressful summer, many turf areas are looking less than perfect and now is the optimal time for reestablishment. Competition from annual weeds, such as crabgrass, is absent and shorter day length means less time for daytime drying. Recently, we’ve been fortunate to have timely rains that have kept the turf growing, but if the rains diminish as we move into September, the primary challenge with any turf reestablishment is maintaining soil moisture. The following six-step establishment primer will help ensure any attempts to grow new turf this fall are successful.
1. Reseeding damaged areas
The first decision that needs to be made is whether to spot-seed the bare areas or if the whole area needs to be reseeded. This decision is basically one of practicality. If the turf was simply thinned or there are small patches of dead grass about the size of baseballs, a fall fertilizer application and favorable weather conditions should help the existing turfgrass to recover and fill in those bare spots. If the damaged areas are the size of soccer balls or larger, or if the area only has sporadic turf plants, then overseeding is going to be necessary to restore the area to turf.
2. Tools to renovate
There are a number of different methods to ensure that reseeding efforts are successful. First and foremost, you must ensure that you get good seed-to-soil contact – seed sitting on top of the soil or simply broadcast spread onto the turf without creating any holes or slits will feed the birds, but not be much use for growing new turfgrass.
There are several options for creating the holes and slits to ensure seed-to-soil contact. Machines such as core aerifiers, power rakes, slit seeders, or even hand raking small areas will 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 soils.
For areas that suffered extensive turf loss, slit seeders are the best option. Slit seeders create a slice in the soil that the seed falls directly into and ensures good seed-to-soil contact. Many lawn care companies offer this service, or if you’re a do-it-yourselfer, these devices might be available at a local rental store.
3. 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 homeowners have after overseeding is that the newly seeded turf has a drastically different color and 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, so 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 key words on the seed bag such as Turf type, Improved, or Dwarf when selecting tall fescue cultivars. I would avoid the standard Kentucky 31 (K-31) tall fescue for use in home lawns due to its wide leaf blade. However, if you’re looking to spruce up a minimal maintenance or acreage type landscape, K-31 can be a good choice. Turf type tall fescue is now being mixed with Kentucky bluegrass and is more widely available to consumers than it was just a few years ago.
Please see our fact sheet on Purchasing Quality Turfgrass Seed: Read the Label at www.turf.msu.edu under the Home Lawns section for more tips on purchasing seed. Overseeding rates for Kentucky bluegrass are 1.5 to 2 lbs./1,000 sq. ft. For mixtures containing perennial ryegrass or fine fescues, rates should be increased to 3 to 5 lbs./1,000 sq. ft. For tall fescue seeding, not overseeding, the rate is 6 to 8 lbs./1,000 sq. ft. Strive to incorporate the seed to a depth of about 0.25 inches. Deeper planting depths may result in some of the germinating plants not making it to the surface.
4. 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 one bale of straw per 1,000 sq. feet. Be careful with the amount of mulch you apply; you don’t want to smother those young seedlings. Apply enough so you can still see about 1/3 to 1/2 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, just don’t spread them too thick over the area.
5. Fertilizer, irrigation, and herbicides
At the time of seeding, apply a starter fertilizer at a rate of 1 lb. N/1,000 sq. ft. to help those young seedlings get established. A starter fertilizer is a fertilizer with a N:P2O5 ratio similar to 1:1 or 1:1.5. 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, e.g., 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. Always make sure to read and follow the label directions before applying any herbicides.
Finally, don’t be afraid to get out there and mow the new turf. It’s always challenging to set absolute guidelines when talking about when you should start mowing new seedings. My recommendation is 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 next spring.
Dr. Frank’s work is funded in part by MSU’s AgBioResearch.