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Is Aerating Your Lawn in Fall Really the Best Time?

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As any lawn care professional will tell you, aeration is key to maintaining a healthy lawn. But when is the best time to aerate? Fall has long been considered the best time to aerate, but is that really true? And does the type of grass you have or the extent of the problem make a difference?

If your lawn starts to pool water, looks brownish in color, develops a thick thatch, or shows signs of thinning or bare patches, these are all signs that your lawn is not getting enough water, air, or nutrients. There could be a number of reasons but one of the most common is compacted soil and a lawn in need of aeration. But do you wait until fall or act sooner? Let’s take a closer look at these important questions.

The best time to aerate your lawn is when it is in need of it. Waiting could aggravate the problem and leave your lawn stressed for longer. Furthermore, if you are going to overseed, you should do so just before your grass enters its peak growing cycle, which varies depending on the type. Your aeration schedule should be determined by these factors.

What is lawn aeration and why is it important?

What is lawn aeration and why is it important?

Lawn aeration is the process of making small holes in your lawn so air, water, and nutrients can penetrate the soil more easily. 

You can aerate a lawn using a garden fork, a spike aerator, or a small plug aerator. If though, you have a large lawn, then it is much easier to use a larger dedicated tool such as a machine-driven core aerator.

Core and plug aerators remove plugs of soil from the ground, making larger and deeper holes than a garden fork. The depth of the holes made by a core aerator will depend on the model, but they are typically 3-4 inches deep, and the soil plugs removed can be left to break down back into the top of the soil.

Why Is Soil Aeration Important?

Soil aeration is important because it can relieve soil compaction. Soil compaction prevents or hinders the oxygen circulation and moisture levels in the soil and stops nutrients from being delivered to plant roots.

The result is that the grass roots find it difficult to penetrate the compacted soil, instead forming a shallow root structure on the surface of the soil substrate which struggles to find enough nutrients to properly thrive. 

Core aeration allows you to deal with excessive thatch, improve drainage and microbial activity, and help nutrients travel deeper into the substrate. All of which are important for keeping your lawn healthy and thriving.

Soil Compaction

Soil Compaction

Soil compaction is a major problem for many lawns. It happens when the soil is packed down too tightly, preventing air, water, and nutrients from getting to the roots of your grass. This can lead to unhealthy grass and even bare patches. Lawn aeration can help relieve this compaction and improve drainage.

Improved Drainage

Lawn aeration is also important for improving drainage. Poor drainage is a common problem in lawns, especially if the soil is compacted. Aerating your lawn can help to improve drainage by allowing water to seep down through the holes into the subsoil below. This can help to reduce puddling and prevent waterlogging.

Thinning Out and Bare Patches

Even though your grass may appear to be in good shape right now, when the weather gets warmer it could start to turn into a patchwork pattern as bare and thinning areas appear. This is especially the case if you are prone to cold freezing winters with snow laying on the grass for extended periods. 

A patchy lawn can be remedied by aerating, seeding, and fertilizing. These measures will help ensure that bare areas are revived as new grass will grow to fill the gaps.

Invasive Weeds

A patchy lawn will inevitably allow weeds and crabgrass to take advantage of stressed or overworked lawns to spread throughout your garden and spread further. Your grass plants will have to compete with weeds water and oxygen in the soil, and if there are insufficient nutrients present, the weeds will dominate and have a greater chance of thriving.

Why is Fall the Common Time to Aerate

There are a number of reasons why fall is the most common time to aerate most notably it is at the end of the summer season when your lawn is likely to be most in use.

Firstly, the cooler fall temperatures provide ideal conditions to allow the grass to recover more quickly from the aeration process.

Secondly, the hard summer months can take a toll on your lawn, and aerating can help it recover from all the foot traffic as it is often during this period compaction occurs.

Finally, cool-season grasses have two peak growing seasons in early spring and in fall, while during the hotter summer months their growth rate is much reduced. Therefore, fall is often used because it allows both recovery from summer traffic and the grass roots, which are still growing, to extend down in the opened cores promoting deeper roots and new and stronger growth. 

However, warm-season grasses work to a different growing cycle than that of cool-season grasses, and as a result, fall isn’t necessarily the best time to aerate a warm-season grass lawn 

How Warm-Season and Cool-Season Grass Impact the Timing of Aeration

How Warm-Season and Cool-Season Grass Impact the Timing of Aeration

Warm and cool-season grasses grow and go dormant at different times based on soil temperature. Warm-season grass goes dormant at 65°F while cool-season grass goes dormant when the temperature drops below 45°F, some twenty degrees lower. In addition, the growing cycle for cool-season grass slows right down when temperatures reach 75°F  

This difference in timing of peak growth and dormancy between warm-season and cool-season grass, and whether you are planning to overseed the lawn after aerating, should have considerable influence on the timing of aeration.

As we have discussed one of the key reasons to aerate is to allow the root growth to penetrate deeper into the substrate. For this to happen you should be looking to aerate just before the peak growing season for your types of grass. In terms of warm-season grass, if you allow the temperature to drop below  65°F then the grass won’t grow down into the newly created cores.

Obviously, local climatic conditions play a huge role in the timing but if you live in a traditional zone and have warm-season grass then, if you leave it too late into the fall, aeration won’t be as effective. 

As summer is the peak growing season for warm-season grasses, such as Zoysia or Bermuda, the best time to aerate and overseed will be in the spring and summer as the grass reaches its peaking growing season. 

For cool-season grasses, early spring or fall are both good times to aerate when the temperature is between 45°F and 75°F. This gives you a lot more flexibility than with warm-season grass and fall may well be the perfect time to aerate to help the lawn recover from summer traffic.

However, this may vary based on the conditions your lawn experiences throughout the year. For example, if you experience a lot of foot traffic or areas that get watered frequently, you may need to aerate twice a year. Likewise, if you have heavy clay soil, you may need to aerate more frequently.

Should You Overseed After Aerating?

As we have seen different grass types enter their peak growing seasons at different points of the year, so if you are going to overseed this timing will influence when you aerate. This is because, as a rule, it’s best to seed your lawn after aeration. Overseeding after aeration ensures that the seed you sow will have plenty of access to nutrients, moisture, and air.

However, there are some situations when overseeding should be avoided especially when climate conditions impede seed germination.

There are also times when your soil has become so compacted that waiting for the peaking growing season to aerate could harm the long-term health of your lawn. As such if you have cool-season grass and find that your lawn needs aerating in late spring or the middle of summer after temperatures have reached 75°F then you shouldn’t overseed after aerating.

Likewise with warm-season grasses. It may be prudent to wait until your lawn has recovered from the stresses of summer heat and if you find the temperatures have dropped below 65°F then you shouldn’t overseed after aerating.  

If you have a general lawn care strategy that includes annual aeration and overseeding then it is best to carry this out just before peak growing season. This doesn’t mean that you can’t aerate at other times of the year if your grass surface shows signs of compaction, but putting down grass seed at these times won’t be as effective.

Problems with Aerating and Overseeding in Spring and Summer

One of the main reasons that fall is preferred to spring when aerating and overseeding is that there is less potential for weed growth crowding out the new grass growth.

If however, you have properly treated your lawn with pre-emergent to prevent common weeds such as crabgrass and both broadleaf weeds from germinating this shouldn’t be a problem.

Summary: Rethinking Lawn Aeration

As a general rule of thumb, fall is the best time to aerate a lawn, if necessary. This is due to the fact that your lawn will recover faster from the aeration process when the weather is cooler and there is more rainfall. However, the exact timing of aeration should be decided by the type of grass that you have, either warm or cool season, and whether you are going to overseed.

Because of this both spring and summer are also options, particularly in terms of warm season grasses , however, you can also aerate your lawn if you feel it is necessary.

Ultimately it is important to aerate your grass regularly as it alleviates compacted soil which in turn allows better drainage, and oxygen circulation and allows the nutrients to access the grass roots more easily. All of which contribute to promoting thick, healthy grass growth and a beautiful lawn.