Quick Answer
You should wait 2-4 weeks after aerating before seeding your lawn. Aeration creates holes in the soil that allow better water, nutrient, and oxygen flow. It takes time for the soil to settle so there is good contact between seed and soil. Seeding too soon after aeration can result in seeds being buried too deeply. Wait 14-28 days for the best results.
When to Seed After Aeration
Aerating your lawn provides many benefits. It relieves soil compaction, helps break up thatch, and improves drainage. The machine used to aerate your lawn creates small holes across your yard by pulling plugs of soil out of the ground. This leaves the lawn full of open holes that allow air, water, and nutrients to better reach the grass roots.
However, this newly aerated soil needs time to settle back down before seeding. If you seed too soon after aerating, the grass seeds can end up being planted too deeply within the aeration holes. This makes it difficult for the new grass to sprout and establish.
The ideal time to wait between aerating and seeding is 2-4 weeks. This gives the soil enough time to naturally settle back down, while still being soon enough to take advantage of the improved seed to soil contact from aerating.
2 Weeks
Waiting at least 2 weeks allows basic settling of the soil. This ensures good contact between the grass seed and soil below. If you seed too soon, the seed can end up buried within the holes at uneven depths. The soil needs time to slightly fill in the holes and create a more level surface for planting.
After 2 weeks, the aeration holes will still be visible, but the sides of the holes will have started to deteriorate. This allows seed dropped on the surface to fall into the holes, while still making contact with the soil beneath.
3-4 Weeks
A 3-4 week wait provides even better results. Within this time period, natural processes like rainfall, irrigation, earthworms, and microbial activity help settle the soil further. The aeration holes become shallower and less defined.
This allows seeds to land on a relatively flat surface with some indentation from the aeration holes. The seed makes good contact with the soil, increasing germination rates. Waiting longer than 2 weeks provides the best environment for establishing newly seeded grass.
Process After Aerating
Here is a general timeline to follow when seeding after aerating:
Week 1
Aerate the lawn. This can be done in early spring or fall when temperatures are cool. Fall is the best time to both aerate and seed cool season grasses like fescue. The soil cores pulled up by the aerator should be allowed to break down naturally.
Weeks 2-4
Allow the soil to settle for 2-4 weeks. Core break down will be mostly complete and the surface will be primed for planting.
Week 4/5
Conduct any other lawn preparation like adding topsoil or compost to bare areas. Afterwards, seed the lawn. Seed can be spread with a spreader or by hand. Ensure good seed to soil contact by lightly raking over areas after seeding.
Week 6
New grass seeds will begin to sprout. Make sure to water daily to keep seedbed moist. After sprouting, reduce watering frequency to 2-3 times per week.
Week 8
Grass seedlings will be established enough for normal lawn mowing height. Mow new grass at a high setting. Gradually reduce over a month. Avoid heavy traffic on newly seeded areas. Apply starter fertilizer to support growth.
Week 12
Lawn should be fully established. Follow normal fertilization, watering, and mowing practices going forward.
Factors When Seeding After Aeration
Several factors come into play that can slightly alter the ideal time period between aerating and seeding:
Weather
Cool and wet conditions will slow the breakdown of soil cores and settling of the aeration holes. Warmer, drier weather will speed up the process. Adjust timelines accordingly.
Soil Type
Clay soils tend to settle more slowly than loamy or sandy soils after aeration. Allow a little more time between aerating and seeding if you have heavy clay in your lawn.
Lawn Use
High traffic areas will benefit from a slightly longer period between aerating and seeding. This allows more settling time where the soil is frequently compacted.
Seed Mix
Rapidly germinating seed types like ryegrass can be seeded a little sooner after aeration than slower growing fescues or bluegrass. But it’s still best to wait 14-28 days when possible.
Time of Year
Spring and fall are the only appropriate times to aerate and seed cool season grasses. Wait a little longer within the optimal seeding window if aerating and seeding are done close together.
Alternatives to Early Seeding After Aeration
If the timing between aerating and seeding your lawn is not optimal, there are a couple alternatives to seeding immediately:
Late Season Overseeding
If aerating was done too late in fall to allow a 2-4 week wait, an option is to wait and do a dormant seeding over winter. This involves spreading seed once the ground is frozen. Some germination will occur in spring.
Temporary Cover Crop
For spring aerations, a short term cover crop like annual ryegrass can be seeded immediately after aeration. This protects the soil until the ideal window opens up for seeding long term lawn grass seed.
Multiple Aeration Passes
Doing more frequent, lighter aerations allows seeding sooner after each pass. The soil recovers more quickly compared to deep, heavy aerations done in a single pass.
Topdress After Aeration
Adding a thin layer of compost or topsoil immediately after aerating can help fill in holes and provide a more suitable seedbed.
Best Time of Year to Aerate and Seed
Timing both aeration and seeding together takes some planning. Here are the optimal times to aerate and seed cool season grasses:
Fall
The best time to both aerate and seed is early to mid fall. Cooler temperatures and more reliable rainfall in fall provide the ideal conditions for establishing new grass plants. Aerating in late summer provides time for the soil to settle before seeding in early fall.
Spring
Spring is another option, although weather conditions are less reliable than fall. If aerating in spring, aim to seed approximately 4 weeks later once soil settling has occurred and nighttime temperatures are consistently above 55°F.
Summer
Aerating is fine in summer but avoid seeding new grass. The heat and drought stress make it difficult for the new plants to survive. Dormant seeding in winter can work after summer/fall aeration.
Steps for Aerating and Seeding
Follow this complete process when aerating and seeding your lawn:
Aerate
Use a core aerator that removes plugs of soil, allowing air and water movement into the root zone. Cover the entire lawn, making 2-4 passes in perpendicular directions. Leave cores to decompose on the lawn surface.
Let Soil Settle
Allow 2-4 weeks for the soil and aeration holes to settle. Core break down will be mostly complete and the surface will be suitable for planting.
Prep Lawn
Conduct any lawn prep before seeding like adding soil amendments, removing debris, or killing weeds. Level any extremely uneven areas.
Seed Lawn
Select a quality grass seed mix suitable for your climate and conditions. Spread seed using a broadcast spreader or by hand. Follow seeding rate recommendations.
Lightly Rake
Use a leaf rake or lawn rake to lightly work seed into the soil surface. Go easy to avoid burying seed too deep.
Water & Wait
Water frequently to keep seedbed constantly moist. Avoid walking on newly seeded areas until grass is established. Wait 6-8 weeks for full establishment.
Tips for Seeding After Aeration
Follow these tips for the best results when seeding after aerating your lawn:
- Wait at least 2 weeks after aerating before seeding
- Allow 3-4 weeks for best seed-to-soil contact
- Conduct aerations when temperatures are below 85°F
- Leave soil cores on lawn to decompose naturally
- Seed in early to mid fall for cool season grasses
- Use high quality seed mixes appropriate for your area
- Only make light contact between seed and soil when planting
- Water newly seeded areas frequently to maintain moisture
- Allow at least 6-8 weeks for full establishment before heavy use
Following these tips will maximize the benefits of aerating and ensure your newly seeded lawn gets off to the right start.
When Not to Seed After Aeration
There are certain situations when it’s best not to seed immediately after aerating:
- Soil temperatures are above 85°F
- Aerating was done in summer
- Planning dormant winter overseeding instead
- Lawn is prone to heavy weed pressure
- Lawn needs significant grading or slope work
- Summer stresses like heat, drought, or disease are present
- There has not been adequate time for the soil to settle
Hold off on seeding and wait for the next optimal seeding window if any of these apply to your lawn.
Frequently Asked Questions
Is it better to aerate before or after seeding?
It is best to aerate before seeding your lawn. Aeration allows better seed-to-soil contact, drainage, and root development. Wait 2-4 weeks between aerating and seeding for the soil to settle.
Can I put down seed the same day as aerating?
It is not recommended to seed immediately after aerating. The soil and holes need time to settle so the grass seed is not buried too deep. Wait a minimum of 2 weeks after aerating before seeding.
How soon can I mow after aerating and seeding?
Wait until the new grass is around 3 inches tall before mowing. This is usually 6-8 weeks after seeding. Set mower height high and gradually lower over time.
Do I need to add topsoil after aerating before seeding?
Adding a thin layer of topsoil or compost after aerating can help fill in holes and provide a more consistent surface for seeding. But it is not always necessary.
How often should I water after seeding?
Newly seeded lawns need frequent watering to keep the seedbed constantly moist. Water up to 3 times per day, and reduce frequency after grass seeds begin to germinate and establish.
Conclusion
Aerating your lawn provides an excellent opportunity to also reseed bare or thin areas. But it is important to wait an appropriate amount of time after aerating before seeding. Allow 2-4 weeks for the aeration holes to settle so your grass seed can make good contact with the soil below. This will maximize germination rates and establishment success. Follow the tips above for the best results seeding your lawn after aerating.
