Fall is the normal time for aeration and dethatching, but if your lawn looks patchy and tightly packed after a harsh winter, performing the process in the spring restores the look of the yard for the rest of the year.
Aeration involves driving cores or spikes into the ground to bring submerged soil to the surface and introduce fresh air to the lawn. The process helps to reduce soil compaction.
Compacted soil – a term describing ground where the soil particles are pressed tightly together, with very little air between them – occurs slowly over time, underneath the pressure of hundreds of heels. Roots and water both struggle to penetrate compacted soil, which results in the patches of dead, brown lawn.
Walking on wet grass compacts its soil quickly, but aeration cures the problem even faster. Aerating a normal suburb-sized lot only takes a couple of hours.
Aerators come in both manual and powered versions. Manual aerators look kind of like simple push lawn mowers, with a central axis spinning between two wheels – but the axis on manual aerators are covered in jagged, hollow spikes rather than cutting blades. Engined aerators appear similar to gasoline-powered engined mowers, but again, they feature jagged spikes. Manual aerators are cheaper but require more back power, whereas engined aerators are easier to use but are far more expensive.
Regardless of which type of aerator you use, you want to push the machine in parallel rows across the yard, the same way you would a lawn mower. Repeat the process a second time afterward, moving perpendicular to the original rows.
The lawn will be covered in small dirt cores after aerating. That's okay – they'll disintegrate when you dethatch the yard.
Thatch, a thick, interwoven mat of living and dead materials, accumulates on the surface of the soil when grass grows faster than it decomposes – a common situation with heavily fertilized lawns. Thick blankets of thatch prevent water from reaching the soil underneath, depriving grass roots of life-giving moisture and eventually killing a lawn.
Dethatchers come in manual and powered versions, just like aerators. Powered dethatchers also go by the term "vertical mower" and are very, very heavy. You can dethatch grass manually using a specialty dethatching rake, or you can use a basic garden or steel rake.
You'd run a powered dethatcher in parallel rows, similarly to the way you mow or aerate a lawn. Manually dethatch a lawn the same way you would normally rake, albeit much more deeply and vigorously. You only want to see soil and blades of grass when you're done.
No matter how you do it, dethatching stresses a lawn. Most people overseed and fertilize immediately after aerating and dethatching to help ease it back to health. However, as rough as it is, aerating and dethatching your lawn every year or two revitalizes yards and keeps grass growing strong.