Once your lawn has been properly aerated, it will absorb water and nutrients much more easily. Grass will grow much more vibrant blades and develop healthier root systems. Once you have completed aerating you should:
- Allow any soil plugs to break down naturally
- Overseed your lawn
- Water to feed grass roots
- Apply fertilizer
- Apply pre-emergent weed killer IF you are not overseeding
These methods will help you take full advantage of a recently aerated lawn to improve grass health, suppress weeds, and save you a lot of lawn maintenance in the long run.
When Should You Aerate?
Aeration is required when the soil in your lawn is compacted. Compacted soil inhibits grass root growth. If you do not aerate, your lawn will yellow, die, and/or allow weeds to invade. To determine if the soil is so compacted that aeration is necessary, test your lawn with a screwdriver.
- Water the lawn the day before testing the soil.
- Push a screwdriver into the soil.
- If the screwdriver easily sinks 2–4 inches into the soil, it does NOT need aeration.
- If the screwdriver does not easily penetrate the soil, aeration is necessary.
- Test 3–5 different areas in your yard. Soil compaction may be localized to high-traffic areas.
If your soil is in need of aeration, a core aerator is the best option for your yard. A motorized core aerator can be rented from most hardware stores. It is the most effective tool for breaking up compact soil, which allows air, water, and nutrients to penetrate your lawn down to the root layer.
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Dethatching vs. Aerating: Do One or Both?
Much like compacted soil, excessive thatch buildup (more than 1 inch thick) starves the soil of water and nutrients. A core aerator will help to break up thatch, but for best results, dethatch before aerating.
Dethatching your lawn will strip out the spongy layer of thatch on top of the soil. This will allow your core aerator to reach down to the soil more effectively. To bring life back to a failing, thin lawn, dethatch and then aerate.
What is the Best Time of Year to Aerate?
Spring is traditionally considered the best time to aerate. A spring aeration run allows your lawn to take advantage of the newly loosened soil through the growing season. However, some grass responds best to aeration in the fall. Correct aeration timing depends on the type of grass in your lawn.
Best Aeration Timing by Grass Type
- Warm-Season Grasses: Spring to early summer
- Cool-Season Grasses: Early fall
Warm-season grasses, such as Bermuda and St. Augustine, should be aerated in spring (March through April) but may tolerate aeration in early summer (May through June). Fertilization, overseeding, and other processes also have the best benefit at this time, so plan to aerate your warm-season grass lawn in spring.
Cool-season grasses, such as Fescue and Ryegrass, perform better if aerated in early fall (late August through September). Cool-season grasses also respond best to dethatching, fertilizing, and overseeding in fall. In order to gain the biggest benefit from cool-season grass aeration, plan the job for autumn.
What Should You Do After Aeration?
Once you’ve aerated your lawn, there are several different tactics you can use to improve lawn health. Is your goal to thicken your existing grass? Salvage a struggling lawn? Control invasive weeds? Depending on what your lawn needs most, take advantage of newly aerated soil to make the biggest positive impact possible.
Allow Soil Plugs to Break Down Naturally
After you use a core aerator, plugs of soil will be scattered across your yard. While it may be tempting to take some measures to clean up your yard, the best course of action is to leave plugs after aerating and allow them to break down over time.
Mowing and regular lawn use, as well as precipitation, will gradually destroy soil plugs. With regular lawn maintenance, the soil plugs in my yard were gone within a few short weeks
This allows air and nutrients to mix with the soil, and allows water and fertilizer to easily enter the holes left by core aeration.
Best for: All lawns. Soil plugs left by an aeration machine should always be allowed to break down over time.
Overseed with New Grass
A core aerator leaves evenly spaced holes 2–3 inches (5–7.5 cm) apart. These holes are the perfect shelter for grass seed. They allow seeds to take root and keep them protected from birds and other scavengers.
After aerating your lawn, spread grass seed over your lawn using a broadcast spreader. Then, properly water and care for your newly overseeded lawn to promote great results.
Best for: lawns with thin, sparse grass or bare patches where grass has died.
Apply Pre-Emergent Weed Killer (Only if You Do Not Overseed)
Pre-emergent herbicide kills plants as they sprout. It will stop any grass and weed seeds from growing for up to 6 weeks after application. Keep in mind, because it stops grass seeds from growing, you can’t apply pre-emergent if you’ve overseeded in the past 4 weeks or plan to overseed within the next 6 weeks. It will kill grass seedlings as well as weeds.
If you have a thick, beautiful lawn and don’t plan to overseed, you should apply a pre-emergent weed killer after aerating. The holes left by the aerator tines allow the herbicide to enter the soil and create a barrier that kills weeds as they sprout. Your herbicides will perform much better when applied just after aeration.
Best for: Lawns with yearly weed problems. DO NOT apply pre-emergent if you have overseeded or plan to overseed.
Recently aerated soil draws any fertilizer down deep into the ground, where it feeds grass roots and has a big positive impact. For a healthy lawn, apply a high-nitrogen, organic fertilizer after aeration.
Milorganite is an excellent fertilizer choice for established yards. It’s a slow-release fertilizer, so it delivers nitrogen over an extended period of time and will not burn your yard.
Lawn starter fertilizers can also be used, but it’s important to keep in mind that starter fertilizers tend to have a much higher phosphorus profile than Milorganite. Phosphorus is a fantastic nutrient for helping new grass seed establish deep roots, but adding too much to the environment can be detrimental to surrounding areas. I live in an area with a lot of freshwater around, so I like to limit my phosphorus use as much as possible to prevent runoff.
- Helps green up your lawn within a few weeks.
- Can be used on your lawn, trees, flowers, and shrubs.
- Slow-release fertilizer and does not contain any salt.
The holes in your yard left by the aerator tines will not only help the fertilizer penetrate the soil, they will also prevent the fertilizer from washing away.
Best for: A recently seeded lawn or an established lawn where grass is growing poorly.
Provide Adequate Water
After aerating, water your yard thoroughly. Continue watering deeply 2 times per week (30–60 minutes per watering session). This encourages grass root growth for any new seeds as well as existing grass plants.
Ground that has been compacted by foot traffic or vehicle traffic does not absorb water well. Attempts to water will run off compacted soil, starving grass. One of the best things to do following aeration is to establish a proper watering schedule to revive failing grass.
Best for: Lawns with yellowing/browning grass.
How to Treat Your Lawn After Aerating
The best way to care for your lawn after aeration is by allowing the soil plugs left after aeration to decompose naturally, establishing a regular watering schedule, fertilizing with a high-nitrogen fertilizer, and either overseeding with new grass or applying a pre-emergent herbicide to stop weeds from sprouting.