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Your lawn needs to breathe, and aeration can help. Lawn aeration involves the removal of small soil plugs or cores out of the lawn. Most aeration is done mechanically with an aeration machine.

As lawns age or sustain heavy use, soil compaction can result. Roots require oxygen to grow and absorb nutrients and water and compaction reduces total pore space and the amount of air within the soil. Core aeration can benefit your lawn by:

  • Increasing the activity of soil microorganisms that decompose thatch
  • Increasing water, nutrient and oxygen movement into the soil
  • Improving rooting
  • Helping prevent fertilizer and pesticide run-off from overly compacted areas

Do I need to aerate?

If in doubt about aeration, take a core sample of your lawn and subsurface least 6 inches deep. If grass roots extend only into the first 1-2 inches, your soil may be compacted and could benefit from core aeration. Expect a seasonal effect with cool-season grass roots being shortest in late summer and at their greatest depth in late spring.

Other reasons to aerate include:

  • Your lawn is heavily used, and the ground is hard and compact
  • The thatch layer is in excess of a half inch
  • You have a heavy clay soil

However, not all lawns need to be aerated. Keep in mind that winter freezing and thawing cycles and earthworm activity can help loosen slightly compacted soils. Furthermore, newly seeded or sodded lawns should not be aerated in the first year. Lawns with more than half an inch of thatch may require dethatching.

How do I aerate my lawn?

Aerators can be rented from many garden or rental centres, and some landscape companies will perform the service for you. Be sure that the machine has hollow tines or spoons to bring the soil core to the surface. In Alberta, the best time to aerate is in May to June and again in mid September.

When aerating,

  • The soil should be moist but not wet.
  • Lawns should be thoroughly watered two days prior to aerating, so tines can penetrate deeper into the soil and soil cores easily fall out of the tines.
  • If aerating after prolonged rainfall it is important to wait until the soil has dried somewhat so soil cores do not stick in the hollow tines.
  • Aerate the lawn in at least two different directions to insure good coverage. Be careful on slopes, especially steep ones, as well as near buildings and landscape beds.

Additional information on aeration

Before aerating, please keep the following in mind:

  • Aeration helps to control thatch.
  • It is extremely difficult to core aerate heavy clay soils.
  • Aeration is not recommended for soils that have stones, rocks or tree roots just below the soil surface.
  • Be sure to mark sprinkler heads, shallow lines from sprinkler, underground utilities, cable, and septic lines before aerating so they will not be damaged
    Soil cores are best left on the lawn surface; they typically work back into the grass in 2-4 weeks.
  • Lawns may be fertilized and seeded immediately following aeration with or without further soil topdressing.
  • Lawns can be aerated once a year, especially under heavy use conditions.

For more information, visit YardSmart.​​​​​