Should I aerate my lawn?

Asked March 13, 2020, 4:11 PM EDT

We put tall fescue sod down in the fall of 2018. It has not fared well, and about 40% is now exposed soil. Two overseeding attempts last fall were unsuccessful (in part, at least, because many seeds were washed away by biblical deluges). I plan to overseed again this spring. How can I judge whether the ground needs core aeration? Thank you Steve

Benton County Oregon

3 Responses

Hello. In general, if your soil is compacted by heavy foot traffic and or machinery yes aeration could help alleviate compaction. I have loads of questions to be able to answer this question thoroughly. First was the sod installation a lawn renovation or a new lawn installation? What time of year was it installed? Was the ground properly prepared prior to the sod installation? How much sunlight does the yard get? Did you apply fertilizer at the 4-6 week time period? Finally, was it kept moist? Ditto for the over-seeding attempts. Optimum temperatures for seeding lawns are 60 to 85 degrees. (Mid-August to Mid-September around here.) It requires proper preparation of the soil, selecting the proper seed mix for the location, sun exposure, and constant light moisture. Drying in between irrigation or rain showers does not make for good germination. I have included a link below about establishment or restoration of a lawn using seed or sod. This OSU Extension publication goes through all the steps required to prepare your soil for either type of grass installation. The soil preparation is basically the same for both types of grass installation and is important for success.

Practical Lawn Establishment and Renovation

I have also included a comprehensive guide to lawn maintenance and the different approaches that can be taken. Basically mowing, irrigating, fertilizing. How often, how much and what grass requires to be healthy and thick. I hope that this information

helps you.

Practical Lawn Care for Western Oregon

Thank for your response. I am happy to provide more details. At the end I have a few follow-up questions:
*First was the sod installation a lawn renovation or a new lawn installation?
The sod was laid in October 2018. It was a new installation after the backyard was completely destroyed and remade, with the addition of low walls, a patio, and a paver walkway.

*Was the ground properly prepared prior to the sod installation?
A 6-8" layer of soil was laid down over the base. The hardscaper/landscaper said it was very good for sod. They're a small reputable group, so I assume they put down the right material. I recall being told a mixture of sand, silt and clay, but I don't know for certain.

*How much sunlight does the yard get?
I'd characterize the yard overall as ranging from part sun to part shade. About 80-85% is part sun, and the fescue seemed to do very well. I don't know how many hours of direct and filtered sunlight there is, because it changes throughout the day. There's a corner, maybe 10-15%, that's closer to part shade. The growth rate is slower for sure.

* Did you apply fertilizer at the 4-6 week time period?
Fertilizer was applied when the sod was laid (or shortly thereafter), I don't recall if there was a follow-up after 4-6 weeks. There was another application in spring 2019 for an overseed done by our mow and blow folks (I bought a lawn mower, so now I do it all myself). Then I fertilized after the failed overseeding last October.

* Finally, was it kept moist?
It had plenty of water while the sod was "taking." Over the summer, I watered regularly and kept it moist. We have a timed irrigation system. But in a few relatively small areas, mostly near edges, the soil dried out and the grass didn't are as well. I probably noticed the problem in July. My solution was to wet the dried area and "aerate" it by pushing the tynes of a garden fork into the harder soil. Doing this daily for a few weeks softened things up and allowed water to reach deeper into the soil, and overall it really helped.

Based on your original answers, and the information in the links, my plan is this for a spring overseed:

1. Wait until the soil temperature is >60 (hope a meat thermometer works); 2. mow the lawn relatively short (but not nearly as short as I did last fall. That was a disaster and the grass that has survived is just now really recovering); 3. Rake the yard to open things up and clear out debris (acorns seem nearly impossible to get rid of though) 4. Spread a very thin layer of topsoil over the existing lawn. I don't think aeration is needed. In most places, I can push my finger down and make an indentation. It does feel like there's a good deal of clay, even in the sod layer; 5.Overseed; 6. fertilizef; 7; spread very thin layer of topsoil; 8: walk over everything, or figure out some other way to push the seed down (I don't have a roller, and unless the stay-at-home situation changes I won't be going out to rent one soon. 9: keep the soil moist.

Follow-up questions:
1. Does the plan seem generally sound?
2. What kind of topsoil would you recommended for the pre-seeding preparation and the after seeding covering (very thin (maybe 1/8th inch)
3. Is tall fescue still my best bet, even for the area that's less sunny.
4. Am I missing anything?

Thank you

Hello again. Your plan has a couple things that may need to be revisited. The first is the recommended use of a dethatcher in the lawn renovation portion of the first document in my first note. Not only does this machine remove unwanted lawn materials it will help to break up the soil and once the debris is raked up will provide a decent bed for the new seed. You could possibly skip the step of putting down soil before seeding. You mention the tough removal of acorns, to me that infers shade.

While tall fescue is shade tolerant in Western Oregon it prefers hot dry areas. It has disease issues in Western Oregon. You may do better with a mixture of seeds since your area is part sun and part shade. Call a local grass seed company (not a big box store) and discuss their available seeds to match your yard’s conditions. Keep in mind that after several years your yard will have many varieties of grass in it unless you work very hard to maintain a single variety and therefore color. If you are worried about matching the sod that survived, then try tall fescue again. Keep in mind that it did not seem to do well at your location.

My meat thermometer temperature range starts at 100 degrees. You can purchase a soil thermometer locally for around $10-15. It is easy to use and made for the task at hand. As temperature and moisture are the two keys needed for good grass seed germination find one to check your soil temperature. Shady areas of you yard will most likely remain cooler longer.

I recommend that you explore the hydro mulch option. The seed is mixed with a coating of mulching material and is sprayed on wet. The mulch protects it from drying too much in between watering sessions. Hydro mulch would solve the problem of putting down a thin soil/compost layer over the newly deposited seed. I say this as a 1/8th inch layer of anything is very hard to get right. hydro mulch fixes the issue. Good luck with your project!