In the mad rush to ensure your lawn is mowed, weeded, fertilized and irrigated, the need for aerating is often overlooked. But, as sod ages, the soil underneath can become so compacted, there is little or no pore space (small pockets of air held in the soil), making it difficult for grass roots to absorb water and nutrients. Before long, the lawn will deteriorate, becoming more susceptible to weeds and attack by insects and diseases.
Aeration involves the removal of small cores—or plugs of soil—which are then deposited on the surface (they’ll work their way into the grass within a month). The small holes that remain help to break up compacted areas and allow water and air to penetrate to the root zone.
To determine if your lawn needs aerating, cut out several sections of turf grass, about 15 centimetres square and at least 15 centimetres deep. Examine the clumps, and if the roots extend down only two to five centimetres, it’s probably time to aerate. (Bear in mind, though, that grass roots are longest in late spring and shortest in late summer.) The best time to aerate is early summer or early autumn, when the lawn is growing most actively. Unless freshly installed sod has been laid over compacted subsoil, as is often the case in new subdivisions, typically only mature lawns should need aerating.
There are many different types of aeration equipment. Manual (foot-powered) aerators that cut a plug as you push them into the soil, then release it when pushed into the soil again, are useful for small areas of the lawn and in tight corners.
Powered core aerators (many of which look like self-propelled snow blowers), meanwhile, have hollow tines mounted on a disc or drum that remove the plugs. Holes are typically one to two centimetres in diameter and anywhere from three to 12 centimetres deep, spaced five to 15 centimetres apart. (Keep in mind that aerators that just punch holes into the soil without removing plugs are not as effective as the core models.)