Why do lawns need to be aerated?

lawn aeration
Is this the footwear of a psychopath, a heavy-metal fashion accessory or just another way to keep your lawn lush?
©­ iStockphoto.com/Gennady Kudelya

­Your new neighbors seemed so normal at first. Everyone seemed to take such good care of their yards, the streets were quiet and the neighborhood association even brought you a fruit basket. Then, one day, the stabbings began.

First, you noticed Carl from across the street repeatedly jabbing some kind of two-pronged spear into the ground. Then you caught sweet Mrs. Mackey walking around her lawn with rows of 2-inch (5-centimeter) steel spikes strapped to the soles of her shoes. Before you knew it, the other neighbors were at it as well, pushing around spike-wheeled machines that looked like something out of "Mad Max 2: The Road Warrior." You wondered what was happening to the neighborhood. Why was everyone was so obsessed with stabbing holes into their lawns? Were they fighting off an unseen mole people invasion, or was it a case of lawnicidal madness?


­Good thing you didn't call the police. As it turns out, your neighbors weren't angry at their lawns. In fact, they were just working hard to keep them up through lawn aeration. This perfectly normal outdoor chore involves boring holes in a lawn to keep everything growing healthily. The tools involved range from manual lawn aerators you push into the ground ­to spiked wheels and even gas-powered machines that bore plugs out of the ground. They may look like torture devices, but they're essential to maintaining a beautiful, healthy yard. Yes, even Mrs. Mackey's deadly looking footwear is merely a popular lawn aerator tool, not a weapon against the legions of underground mole people.

Still suspicious? Well, on the next page we'll look at the reason soil and grass benefits from aeration and how to go about aerating your own lawn.


Breathe In, Breathe Out: Lawn Aeration

lawn aeration
A tractor aerates a golf course, leaving behind plugs of soil in its path.
©iStockphoto.com/Michael Braun

­As any landscape specia­list will tell you, mole people simply don't pose a risk to the health of your lawn, but soil compacting does. This situation is exactly what it sounds like: Over time, foot and vehicle traffic mash down the soil in your lawn, compacting all the particles. Even regular mowing takes a toll, and poor drainage and wet conditions make matters ever worse. This situation poses a problem to lawns because compacted soil has far fewer air-filled pore spaces. Plan­ts depend on those pore spaces to supply roots with much-needed oxygen. Compacted soil prevents roots from expanding, interferes with water filtration and disrupts nutrient uptake.

Lawn aeration helps alleviate this situation by creating holes in the ground, which allow air back down into the soil and create room for compacted soil to collapse back into a looser particle arrangement. In a way, lawn aeration is much like perforating a tough cut of meat prior to marinating it. The holes you jab in a flank steak better allow the juicy marinade to seep into the meat. Likewise, the holes in a freshly aerated lawn allow air back into the soil.


When the soil is properly aerated, there's more room for roots to expand and for helpful microorganisms to go about their business. Rain and irrigation water is able to soak farther into the ground, and there's less danger of runoff from such potentially harmful substances as fertilizer, pesticide and gray water. Of course, the fact that aeration is good for your lawn doesn't mean you need to do it every day.

First, there's the amount of traffic to consider. A yard that regularly plays host to touch football games will naturally experience much more compaction than a yard that only gets cat and chipmunk traffic. Second, lawns are composed of different varieties of grass that experience different growth cycles. Lawn aeration should take place during high growth periods, which allows the lawn to recover and take advantage of all the new space at the fastest possible rate. Warm season grasses, such as Bermuda grass, are warm season growers and should be aerated in the spring. Cool season growers, such as bluegrass, are best aerated in the late summer or early fall. Therefore, the third factor to consider is climate since local conditions will dictate when your particular grass will be ripe for aeration.

Freshly sodden yards won't require aeration during their first year, but after that, estimates vary depending on the above factors, as well the kind of soil you have. Clay soil compacts more easily and benefits from biannual aeration, while sandy soil compacts at a slower rate and only needs one aeration per year. Gardens also benefit from aeration, though this is typically accomplished through simple tilling and turning of the soil

Ready to grab a spike and join in all the lawn violence? On the next page, we'll look at the equipment and methods involved in lawn aeration.



Lawn Aeration Tools and Methods

lawn aeration
Core aerators cut plugs of soil like these out of the ground.
© iStockphoto.com/Michael Braun

­If you want to perforate your lawn, you can spend tens or thousands of dollars on aeration tools, bu­t all the methods boil down to two basic ways of making holes in the ground. Aerators with solid spikes simply poke holes in the ground. Core aerators, also called lawn plug aerators, on the other hand, use hollow tubes to cut cylinders of soil out and dump them on the surface. Of the two, core aeration works better on high-traffic turfs as they're physically removing portions of the soil instead of merely putting a hole in the soil. Spike-aerated holes have the capacity to fill back in faster, but even the cored-out soil plugs typically return to the grass within a few weeks.

Aerators come in various forms. You can wear lawn aerator shoes or push spiked wheels and gas-powered aerators across the lawn. You can strap rows of spikes to your tractor wheels or you can just grab a pitchfork and start poking. The expensive aerators are also typically available for rent and, if you'd rather not get your hands dirty, you can always hire professional landscapers to perform the task for you.


Once you have the tools you need, you'll want to make sure conditions are optimal for aeration -- even if it's the growth period for your particular variety of grass. Never aerate during a drought or heat wave, as you'll only help evaporate the soil's precious moisture. You'll want to make sure the ground is thoroughly moist, but also not too wet. You want to perforate soil, after all, and driving steel spikes into mud will have roughly the same effect as trying to cut yourself a slice of pudding. Therefore, be sure to water the yard a couple of days in advance if conditions are too dry. This will ensure the lawn receives the equivalent of 1 inch (2.54 centimeters) of rainfall. Likewise, give the yard a few days to dry out beforehand if it's soaked.

Most landscapers recommend making two passes with whatever aeration tool you're using. This ensures that enough of the yard winds up perforated. After you're finished, it's time to irrigate and apply any seeding or fertilizer you plan on using. Depending on what products you apply, you might need to keep all children and pets off the lawn for 24 hours. Also, keep in mind that the soil is open to more than just lawn care products following aeration. If you're experiencing a weed problem, they're likely to take advantage of the open soil as well.

Explore the links on the next page to learn even more about lawn care, grass and even mole people.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • "All About Cool Season Grasses." Seedland. (Dec. 2, 2008) http://www.lawngrasses.com/season-cool/index.html
  • Aveni, Marc and David Chambers. "Aerating Your Lawn." Virginia Cooperative Extension. June 2001. (Dec. 2, 2008) http://www.ext.vt.edu/pubs/turf/430-002/430-002.html
  • "Lawn Aeration - Greenskeeper's Secret Weapon." Blades Lawn Care. 2007. (Dec. 2, 2008) http://www.bladeslawncare.com/mowers/lawnaeration.html
  • "Lawns: Aeration and Liming." HGTV.com. 2008. (Dec. 2, 2008) http://www.hgtv.com/gl-lawns/lawns-aeration-and-liming/index.html
  • Reeves, Water. "Bermuda -- Aerating." Walter Reeves -- Home of the Georgia Gardner. 2004. (Dec. 2, 2008) http://www.walterreeves.com/lawns/article.phtml?cat=27&id=49
  • West, Dawn. "When Should I Aerate?" All About Lawns. 2008. (Dec. 2, 2008) http://www.allaboutlawns.com/lawn-maintenance-care/aerating-and-thatch/when-should-i-aerate.php