Core Aeration & Overseeding

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Written By: Mark Marino

a Massachusetts Core Applicator License holder and owner/operator of Lawn Phix,

Updated on

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Healthy, dark green lawns are attractive landscape additions that can easily separate your property from the competition (your neighbor). True lawn lovers know that to maintain a green lush lawn is more of a marathon than it is a sprint. Achieving a green and weed-free lawn requires more than just mowing and watering it. 

Your lawn needs proper nutrition for it to grow and flourish. Just like proper nutrition is beneficial to our body’s health, the same goes for your lawn. That’s why core aeration and overseeding are essential to the well-being of your lawn. Core Aerating and overseeding your lawn is important for its health, but you have to perform these tasks at the right time for them to be as effective as possible. 

What is Core Aeration?

The process of core lawn aeration involves removing soil plugs through the built-up and excessive thatch layer of soil to improve your cool-season grass’ access to water and key nutrients. Core Aeration removes cores and relieves compaction, and allows air, water and nutrients to reach deeper in the root zone, which helps grow a stronger turf.

Core Aeration is also an essential step before overseeding, as it allows for better seed-to-soil contact. This massively helps filling in thin areas of the lawn and promotes better growth and germination. Spike aerators are another option to aerate the lawn but are not widely used and do not yield the same results of a core aerator. Core aerators do a much better job than spike aerators of breaking up severely compacted soil, and the holes they leave behind encourage healthy root growth and improve access to water and nutrients for the grass.

What is Overseeding?

Overseeding a lawn is the planting of grass seed directly into existing turf, without tearing up the turf or the soil. It’s an easy way to fill in bare spots, improve the density of turf, establish improved grass varieties and enhance your lawn’s color.

If a lawn looks tired or just “worn out,” if it needs growing amounts of water and fertilizer to thrive, or is disease or insect prone, it’s an excellent candidate for overseeding.

Many older lawns were established with “Contractor’s Mix” turf grasses not suited for the needs of today’s homeowners. They’re often more disease and insect-prone, requiring more fertilizer and water.

Overseeding newer turfgrass varieties into an older lawn can help it better withstand insects, disease, drought, shady conditions, and heavy traffic. The investment in overseeding pays off by reducing the amount of fertilizer, water, and pesticides required. Most importantly, an overseeded lawn stays greener and looks thicker and healthier. 

In New England, the best time to aerate and overseed a lawn is late in the summer or early in the fall, as this is the time when there’s more moisture in the soil and also when cool Fall air will encourage growth. The cool-season grass in New England is bursting with growth in the Fall months and there is much less competition with weeds when trying to establish new growth.

It’s best to NOT aerate during times of drought and during extreme heat. Core Aeration during these times not only allows too much moisture to evaporate from the soil, but it also stresses and weakens the lawn. 

Toro Core Aerator Machine
Core Aerator Tines

When is the best time to aerate a lawn?

Towards the end of the growing season. For cool-season lawns,. this means late summer and early fall. Early spring is the next best option.

When is the best time to overseed a lawn?

In the late summer and early fall is the best time to overseed a lawn. Warmer soil temperatures coupled with cooler daytime temperatures and less competition for weeds make this prime time for overseeding. Overseeding in the spring possesses many challenges ranging from fungus and weeds to late frosts killing the young grass, and not having enough time to establish deep roots to survive the summer.

Pat Burns is the owner of Mass Turf Aeration – providing high-quality core aeration services to the Norfolk County areas of Massachusetts. Mass Turf Aeration is now exclusive using Jonathan Green grass seed for the Aeration and Overseeding season this coming Fall. Follow him on Instagram and book your aeration now at

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Author's Note: this piece has been updated for accuracy since its first publication on
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Author: Mark Marino
My name is Mark Marino, and I am the founder, owner, and operator of Lawn Phix. With a passion for lawn care and turf nutrition for over a decade, I've dedicated countless hours to correcting soil and perfecting lawns. Today, my expertise, backed by formal courses at UMass Extension Pesticide Education, allows me to offer top-tier lawn care services and advice. I am a fully licensed and insured lawn care applicator in Massachusetts, specializing in comprehensive turf nutrition, weed control, and lawn pest control. My license number is AL-0053865. Contact me at [email protected] or +1 (508) 500-8402.

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