Lawn maintenance hinges on a few basic tasks: mowing, feeding, weeding and aerating. Tackle these four tasks faithfully, and your turf will be on a fast track to picture-perfect good looks.
Soil that's compacted on a regular basis needs aeration on a regular basis. Compacted soil puts the squeeze on grass roots, inhibiting their ability to function. If your lawn is frequently driven on, grass probably already looks thin and less than ideal. The weight of a vehicle, even a lawnmower, compacts soil, so it's important to vary mowing patterns to slow soil compaction.
Signs You Need To Aerate
Water puddling on lawn after rain
Vehicles driving or parking on lawn
Thatch layer thicker than one-half inch
Difficulty sticking a screwdriver or a pencil into soil
Heavy clay soil
Thin, patchy or bare grass
Thick stands of Clover in lawn
If your lawn never has been before
Start With A Simple Aeration Test
An easy way to assess soil compaction is to push a screwdriver or pencil into it. Do this in lightly moist soil, not dry. In compacted soil, this task proves very difficult. To confirm compaction, use a shovel to excavate a square foot of turf with soil. If you can easily sink the shovel to a depth of half the blade, your soil isn't compacted. Aeration is necessary if you find yourself struggling to push the shovel into soil.
When you dig up the grass and soil, look for thatch and grass roots. Thatch is a tightly woven layer of living and dead organic material (stems, stolens, roots etc.) that lies between the living grass blades and soil. If that layer is more than one-half inch thick, aeration is needed. Look at grass roots extending into soil. If they reach 4-6 inches deep, your lawn doesn't have a compaction problem. If, however, roots extend only 1-2 inches, you should consider aerating.
Timing on your dig test matters. Cool-season grass roots are longest in late spring; warm-season turf roots peak in fall.
Pick The Right Tool
A variety of do-it-yourself methods make aeration approachable for homeowners of every skill level. Before you begin, decide whether you want to remove soil cores or just poke holes into soil. Removing soil cores opens channels for air to reach into soil. Punching holes serves to compact soil that's already compacted. For aeration, choose from two methods: manual or motorized.
Manual aerators work best for small lawns but don’t produce results that rival automated aerators. You use foot-power to plunge two to four hollow cylinders into soil to extract cores or punch holes. Strap-on spike shoes accomplish a hole-punch effect but don't remove soil cores.
Automated aerators have a circular drum in front or back loaded with hollow cylinders or spikes. With a core aerator that removes soil plugs, look for machines with deeper tines and weight over tines to sink them into soil. Some riding mowers have spike or core aerator attachments.
Another option for aerating is applying an ionized soil conditioner, a solution that loosens clay soil particles and encourages microorganisms that foster healthy soil and digest thatch. However, adding soil conditioners is rarely as effective as core aeration and may take years to be fully effective. A better solution is to have your soil tested, core, then add appropriate soil conditioners based on the results of the soil test.
Renting An Aerator
An aerator is a large, heavy piece of equipment that requires physical strength to operate. Plan on two individuals and a full-size truck bed to move an aerator. Consider partnering with neighbors to share the cost of rental and provide the extra muscle to manage the machine. Typically, the busiest rental times for aerators are spring and fall weekends. If you know you'll be aerating, make your reservation early, or avoid the crowds by aerating on a weekday.
Tips For Success
Before aerating, use marking flags to indicate sprinkler heads, shallow irrigation lines, septic lines and buried utilities.
With lightly compacted soil, sandy soil or soil that's been aerated in the last 12 months, do it in a single pass, following your typical mowing pattern. For highly compacted soil or soil that hasn't been aerated in more than a year, make two passes with the aerator: one following your mowing pattern, and the second at an angle to the first. Aim to create 20 to 40 holes per square foot.
When Do You Aerate? It Depends On Your Turf
Just like you wouldn't mow a lawn that's soaking wet or apply a winterizer fertilizer in June, aeration also requires specific timing. The time of year you tackle aeration and how often you aerate depends on grass and soil type. Lawn grasses fall into two different categories: warm-season and cool-season.
Warm-season grasses begin their period of active growth in summer. If you work a warm-season lawn in late spring to early summer, the ensuing period of rapid growth will quickly fill in the holes you create.
Cool-season grasses emerge from summer dormancy in early fall and grow vigorously during the lower temperatures and reduced weed competition typical during this season. Strong growth helps the lawn quickly recover from the stress of aeration. The caveat on fall aeration is this: Time aeration to allow four weeks of growing time prior to frost. Early spring (after you have mowed twice) is the second best time to work cool-season lawns.
Warm-season turf types — aerate in late spring / early summer:
Cool-season turf types — aerate in fall:
Fescue (Chewings, Hard, Red, Tall)
Ryegrass (Annual, Perennial)
Know Your Soil
Different soil types require more frequent aeration. Clay soil compacts easily and should be worked at least once a year. You can aerate a sandy lawn once a year, or you could tackle the chore in alternating years. In arid climates, aerating twice a year will enhance turf growth and health. But if your lawn is frequently driven on or used for parking cars, you’ll need to annually.
When you know you're going to aerate, do so just prior to fertilizing or reseeding your lawn. Aeration creates openings for nutrients and seed to penetrate soil.
Control weeds prior to aerating, because the process of aerating can spread weed seeds or portions of weedy roots.
Wait for at least a year for newly-planted lawns, so that grass is well established.
Work when soil is moist, but not saturated. The tines of a lawn aerator penetrate moist soil more deeply; soil that's too wet clogs tines. To achieve the correct moisture balance, your lawn should absorb 1 inch of water – delivered through rainfall or irrigation prior to aerating. This may mean you'll water for one hour one day prior to aerating or, if your soil is hard, for shorter times on several days prior to aerating.
Avoid aerating during drought or high heat. If you work in these conditions, you'll stress the lawn by allowing heat to dry soil.
TLC For Aerated Lawns
Afterward, leave soil plugs in place to decompose. These cores contain microorganisms that digest lawn thatch. Running over them the next time you mow will break them up, as will a light raking (after they dry out) or dragging a piece of old carpet over the lawn.
You can fertilize and seed lawns immediately following aerating. It's not necessary to add a thin layer of soil or composted manure, but you can. For heavily compacted soils, consider covering the lawn with one-quarter inch of compost (use sand in southern locales), raking it so it falls into aeration holes.
Core aeration brings up weed seeds from lower soil levels. For cool-season grasses, plan to use a pre-emergent herbicide in the spring following fall aeration. For warm-season turf, apply the herbicide the fall after aerating. Do not apply a pre-emergent herbicide at the same time you reseed.
Water your lawn a few extra times following aeration, especially during hot or dry spells.