When can I aerate my lawn in Scarborough



Is there a good time in spring when I can aerate my lawn?


Dear gardener, thank you for writing to the Toronto Master Gardeners to ask your questions about lawn care, and in particular, the timing to aerate lawns.

There are many advantages to aerating your lawn especially if it has suffered from being compacted by too much foot or vehicle traffic. The answer about the best time to do the aeration seems to be spring or early fall. So now would be a good time.

One of the major factors to consider is what kind of grass you have. If you have a cool-season lawn with grass such as fescue, bluegrass, or ryegrass, the best time to aerate is early spring or early Fall, although my two major sources seemed to think that Fall is preferable. They recommend the late spring (June through July) to aerate warm-season lawn, with grasses such as Bermuda grass, zoysia, or St. Augustine, but I think that warm-season grasses are grown less often in Toronto.

The Missouri Botanical Gardens recommends that: “Core aeration should be done just before the most active growth period depending upon the type of grass being grown. For cool season grasses, core aeration can be done in early spring or preferably, early fall. . . . When done during an inactive period of growth, core aeration may contribute to weed problems by opening up new sites. One of the best uses of core aeration is to introduce new seed. The holes provide a moist environment protected from afternoon sun and this is an ideal spot for grass seed to germinate.”

Other relevant advice includes:

  • Never aerate when a lawn is dormant. A general rule is to aerate only when desirable grasses are growing vigorously.
  • Do not aerate in the very early Spring when the soil is saturated. You will compact the soil further.
  • Soil should be moist, but not wet, before aerating. Irrigate the lawn prior to aerating if the soil is dry.
  • Aeration can be done before over seeding. This procedure makes holes for the seed to fall into, therefore increasing seed-to-soil contact.
  • Whatever your type of grass, do not aerate the lawn within one year of planting seed or sod.
  • Core aeration should be performed every one to two years on lawns that receive very heavy foot traffic. Otherwise, aerating every three to four years on home lawns, especially with clay soils that we have in Toronto, is sufficient.
  • Soil plugs should be left on the surface of the lawn. They will decompose in a couple of weeks.

For more details please see:

An article on lawn-care in general from OMAFRA (Ontario Ministry of Agriculture and Food and Rural Affairs of interest: http://www.omafra.gov.on.ca/english/crops/facts/08-025w.htm

The University of Maryland’s Extension: https://extension.umd.edu/resource/lawn-aeration;

The Missouri Botanic Gardens: