Solved! Here’s Exactly When You Should Aerate the Lawn
Help your turf thrive by aerating the lawn at these times.
Q: I recently moved down south from the Northeast and want to keep my new lawn healthy. When is the best time to aerate the lawn?
A: Punching holes into the soil with an aerator, a tool that has either solid spikes or hollow tines, improves the flow of air, water, and nutrients to your lawn. Aerating also solves such problems as soil compaction (an increase in soil density and decrease in soil volume) and excessive thatch (an overly thick layer of dried plant material between the green blades and roots of grass). Simple though the process may sound, proper aeration requires perfect timing. Aeration schedules differ for lawns depending on grass type, soil, and usage habits, so keep reading for all the factors to consider when deciding when to aerate your lawn.
Aerate when turf problems arise.
While there is value in aerating a healthy lawn to help keep turf lush and green, aeration confers the most benefits on turf that exhibits any of the following conditions:
- Dry and/or hard soil. A classic sign of soil compaction is when a lawn feels bone dry and dense to the touch and rock hard underfoot. You may also have difficulty inserting trowels or shovels into the soil. Aeration increases soil moisture and softness by providing grass better access to water.
- Uneven growth. If the lawn contains bare patches where neither grass nor weeds grow, the soil beneath these areas is likely to be compacted. Aeration promotes even growth by providing grass better access to water, nutrients, and air.
- Poor drainage. Rainwater or irrigation often pools in low areas of the lawn because it cannot permeate compacted soil. Aeration improves drainage by improving soil’s absorption of water.
- Excessive thatch. To judge your lawn’s extent of thatch, remove a one-square-foot, four-inch-thick slice from the top with a shovel. If the thatch layer is more than one-half inch thick, aerate the lawn. Aeration reduces thatch buildup by boosting the activity of soil microbes that decompose thatch.
- High traffic. Aeration can reduce soil compaction in lawns that frequently get trampled by heavy equipment (e.g., riding mowers) or foot traffic from pets or children.
Settle on a season for aeration based on grass type.
To ensure that holes in the turf left by aeration are quickly filled with new grass, aerate the lawn only in seasons marked by high grass growth, which vary by grass type:
- If you have a cool-season grass, such as bluegrass, ryegrass, or fescue, aerate in the early spring or early fall. Cool-season grasses commonly grow in regions that experience cold winters and hot summers (e.g., Northern California, the Pacific Northwest, the upper Great Plains, the upper Midwest, and New England).
- If you have a warm-season grass, such as St. Augustine, Bermuda, or buffalo grass, aerate in the late spring or early summer. These grasses more commonly grow in the warm climates of the Deep South and the lower southwest and southeast.
Aeration should not be done during periods of extreme heat or drought, as creating holes in the soil at these times can expose it to more heat, which can further dry out your grass.
Aerate moist soil in the morning.
Plan to aerate when the soil is moist but not saturated (i.e., no liquid pooling on the soil surface), ideally one a day after rainfall or irrigation. Whether you use a spike aerator equipped with solid wedge-shaped spikes that punch holes in the soil or a core aerator equipped with hollow tines that remove soil, the aerator will penetrate more easily—and can create deeper holes—when the soil is moist. Aerate in the morning if possible, as the low temperature and high humidity will prevent moisture in the grass from evaporating.
Determine aeration frequency based on soil type and lawn traffic.
The frequency of aeration depends on the type of soil you have and the level of traffic your lawn gets:
- If you have clay soil or a high-traffic lawn, aerate the lawn once or twice a year; this type of soil compacts the most easily.
- If you have silty or loamy soil, or get moderate lawn traffic, aerate the lawn once a year.
- If you have sandy soil or a low-traffic lawn, aerating the lawn every two to three years is sufficient; this soil seldom compacts, so requires infrequent aeration.
Time aeration based on other lawn care tasks.
Be sure to choose a time for aeration that won’t interfere with other lawn care activities:
- Weed control. While research has shown that aerating your lawn after the application of a pre-emergent herbicide (a chemical weed killer that prevents weed seeds from sprouting) will not hamper herbicide effectiveness, aerate your lawn before applying these products possible so as not to disrupt the chemical barrier that the herbicide forms over the soil.
- Overseeding. If you plan to overseed (the process of planting new grass seeds into an established lawn), aerate before overseeding to increase contact between seeds and soil. This way, a higher percentage of the new grass seeds will germinate.
- Fertilization. Fertilizer works best when it reaches deep into the soil where the grass roots can access it, so plan to aerate before applying fertilizer to create the holes needed for fertilizer to sink deeply.
- Watering. Water soil within 48 hours after aerating it, and continue to water every two to three days for two to three weeks after aeration, to aid in the speedy re-growth of holes in the turf.
- Mowing or establishing sod. Both mowers and lawn rollers used to establish contact between newly laid sod and soil can compact soil, so always aerate after mowing or laying sod to help loosen the compacted soil.