The best time to aerate and overseed a lawn is late spring to early summer for warm-season grasses and late summer to early fall for cool-season grasses. That’s when the weather allows the best germination rates and healthy growth.
Aerating before overseeding ensures good seed-to-soil contact, deep roots and healthy grass. We discuss the best time to aerate and overseed your lawn with all the tips you need to get it right.
Best time to aerate and overseed cool-season grasses
The best time to aerate and overseed cool-season grasses is late summer to early fall. That’s when the cooler nights and warm days best support their growth. The summer heat subsides, and the soil stays moist for longer, providing enough humidity for grass seeds to imbibe and germinate.
Wait until soil temperatures fall below 65 degrees Fahrenheit. Cool-season seeds germinate best when soil temperatures range between 50 and 65 degrees Fahrenheit, which is also the best temperature range for robust root development.
By then, your lawn also will have exited summer dormancy, welcoming the aeration that removes the thatch layer and loosens the compacted soil around the grassroots.
The second best time to aerate and overseed cool-season grasses is early spring. Aerate and overseed once the soil warms up above 50 degrees Fahrenheit. Allow the lawn to green up a bit before using the aerator. This will help you notice thinned areas and bare patches to cover.
What are the best months to overseed cool-season grasses? The precise interval varies with location:
- In northern states, such as Michigan, the best time is typically mid-August to mid-September or mid-May to mid-June.
- In a transition zone such as Virginia, the best time is mid-August to mid-October or February to April, depending on where you live (South or North).
- In southern states, such as Florida, the best time to overseed your Bermuda lawn with ryegrass for some winter color is October to early December.
Helpful tools and resources:
- The best guide is the soil temperature. Here’s an app that can help you check it for your location.
- To learn more about where aeration and overseeding fit into the yearly lawn care schedule, check our guide, “Lawn Care Calendar for Cool-Season Grass.”
The best time to aerate and overseed warm-season grasses
The best time to aerate and overseed warm-season grasses is late spring to early summer. It’s when summer grasses are actively growing, and the weather is warm enough for them to thrive (80 to 95 degrees Fahrenheit in the air).
Wait until the soil warms up to between 65 to 75 degrees Fahrenheit. Warm-season grass seeds need at least 65 degrees Fahrenheit to germinate and grow robust roots.
When the soil warms up, established grass also starts growing, so aeration fits like a glove, ensuring better airflow and access to nutrients and water for mature and newly seeded grass.
What are the best months to overseed warm-season grasses? As with cool-season grasses, the dates vary with location:
- In the transition zone and southern states, the best time to thicken a warm-season lawn is May to July.
- If you keep a summer lawn with warm-season grasses up north, June and July are the best months for overseeding.
Learn more about timing lawn care treatments for warm-season grasses from our “Lawn Care Calendar for Warm-Season Grass.”
When is the worst time to aerate and overseed?
The worst time to overseed is:
- When there’s still a chance for the last frost of spring
- Too close to the first frost of the year
- During the peak of a hot summer
- During prolonged drought
The weather conditions are likely to kill the seeds and seedlings or, at the very least, make germination and survival challenging. The same conditions make aeration a poor idea since existing grass is dormant or under stress from extreme temperatures.
The exception: Dormant seeding allows you to overseed late fall or early winter when the soil is not frozen. Grass stays in the soil during winter and germinates in early spring. This method requires delicate timing. Learn more from our guide, “What is Dormant Seeding?”
Why should you aerate before overseeding?
Aerating before overseeding ensures good seed-to-soil contact and a high germination rate. Core aeration cuts tiny plugs out of the soil, leaving small holes behind where most grass seeds land. This simple action brings valuable benefits to your lawn:
- Seeds that get into the aeration holes have better contact with the soil.
- Below the soil surface, grass seeds are also protected from heat, dryness, wind, runoff, and birds.
- Aeration improves airflow and helps nutrients and water reach the root system faster.
- Loose soil supports deep and healthy root growth.
There are two types of aeration: core aeration and spike aeration. The University of Illinois recommends core aeration for overseeding: “Core or plug aeration works best as it removes a plug of soil, whereas spike aerators can cause more compaction by pressing soil together around the holes.”
You can aerate even if you don’t overseed. Aerate during the growing season for your grass type:
- Summer for Bermuda, Zoysia, centipede, St. Augustine grass, and bahia.
- Spring and fall for Kentucky bluegrass, perennial rye, and fescues
It’s when the grass benefits the most and recovers quickly from cuts and bruises.
Here are some related articles on aeration:
- “How to Aerate Your Lawn”
- “Benefits of Aerating Your Lawn”
- “How Much Does Lawn Aeration Cost in 2024?”
FAQ about aeration and overseeding
How often should you aerate and overseed?
Aerating and overseeding once a year is often enough to fight soil compaction and promote a thick, healthy lawn that can naturally fight weeds, pests, and diseases.
Aerate more often if you have clay soil. Consider a second overseeding the lawn develops bare patches.
What are some signs you need to aerate the lawn?
A few signs your lawn needs aeration are:
- Hard, compacted soil
- Water runoff
- Thick thatch
- Fertilizers that don’t work as well as before
- Thinned grass
- Yellow and bare patches
When do you need to overseed the lawn?
You need to overseed the lawn:
- Once a year, as part of your lawn care schedule
- When you see thinned grass or patches of bare soil and dead turf
- When you need to change the grass type with more resilient varieties or species
Get perfect timing with professional aeration and overseeding
Timing lawn aeration and overseeding can be tricky for homeowners but not for pros. They’ve tested all the good moments. Find an experienced lawn care company with Lawn Love and get your lawn overseeded correctly and at the right time. It’s the easiest road to lush, thick, weed-free grass!
Besides proper lawn aeration, you can also get the pros to take care of mowing, yard cleanup and fertilization.
Sources:
- IFAS Extension the University of Florida (n.d.). Overseeding Florida Lawns for Winter Color. https://sfyl.ifas.ufl.edu/archive/hot_topics/lawn_and_garden/overseeding_winter_lawns.shtml
- Nair, S. (2022, October 26). To Overseed or Not. University of Arizona Cooperative Extension. https://extension.arizona.edu/overseed-or-not
- Pandian, V. (2023, September 1). Over-seeding Lawn in Autumn. Wisconsin Horticulture Division of Extension. https://hort.extension.wisc.edu/2023/09/01/over-seeding-lawn-in-autumn/
- University of Illinois Urbana-Champaign. (2020, September 10). Lawn Aeration and Overseeding. https://extension.illinois.edu/blogs/good-growing/2020-09-10-lawn-aeration-and-overseeding
Main Image Credit: dean | Adobe Stock Free | License
