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. It’s easy to spot the need to cut, fertilize or weed, but knowing if turf needs aeration is not so obvious – unless you know the signs.

In some cases, you don’t really need to test your lawn to see if you should aerate. Soil that’s compacted on a regular basis needs to be aerated on a regular basis. Compacted soil puts the squeeze on grass roots, inhibiting their ability to function – and robbing lush looks from your lawn. If your lawn is frequently driven on, grass probably already looks thin and less than ideal. The weight of a vehicle – even a mower – compacts soil, so it’s important to vary mowing patterns to slow soil compaction.

Heavy clay soil or a thatch layer of more than half an inch also signals the need for aeration. Lawns that show heavy wear and thinning from foot traffic, turn brown quickly when dry weather lingers, or have thick stands of clover are good candidates for aeration. If water tends to puddle after rains, taking a long time to drain, your soil could benefit from aeration. If grass growth stops in the heat of August and soil feels as hard as rock, you need to aerate. Last but not least, if you have never aerated your lawn, chances are you need to, but it’s worth doing a simple diagnostic test to make sure.

A Simple Aeration Test

An easy way to assess soil compaction is to push a screwdriver or pencil into it. In compacted soil, this task proves very difficult. To confirm compaction, use a shovel to excavate a 30 cm² of turf with soil. If you can easily sink the shovel to a depth of half the blade, your soil isn’t compacted. But if you find yourself struggling to push the shovel into soil, maybe even jumping on it, you need to aerate.

When you dig up the grass and soil, look for thatch and grass roots. Thatch lies between the living grass blades and soil. If that layer is more than 1.5 cm thick, you need to aerate. Look at grass roots extending into soil. If they reach 10-15 cm deep, your lawn doesn’t have a compaction problem. If, however, roots extend only 2-5 cm, 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.

Aeration Checklist

Signs that you need to aerate include:

  • 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