Aerating is, without question, the most important thing for a lawn (besides mowing and watering). There are two different kinds of lawn aeration; solid tine or hollow core (plugging).
Solid tine aerating is a bit like traditionally forking over the lawn but is done using a machine. The machine punches holes in the lawn (much deeper and more powerfully than using a hand fork!) The holes can be up to a depth of 4 inches. This method can be used at any time of year but is particularly beneficial in spring and autumn.
When can this be done? Typically, twice a year during spring and autumn – but can be more if needed.
Hollow tine aerating involves metal tubes being pushed into the ground all over the lawn to a depth of about 3 inches (so not as deep as solid tining).
Cores should always be collected and disposed of as left on the lawn they can take a long period of time to break down and form the perfect seed bed for weeds and even moss!
When can this be done? Once a year or in a healthy maintained lawn every two years, again, during spring or autumn.