Aerators help to reduce the build up of thatch in lawns and also introduce air into the soil to prevent soil compaction. Without aeration, soil tends to drain inadequately, slowing the passage of nutrients and water to the roots, which causes the turf's root system to become shallow and weak.

Thatch is primarily made form grass clippings that accumulate above the soil and below the blades of grass, along with pieces of leaves and bits of twigs that have fallen onto the lawn. This layer generally decays naturally, providing nutrients for the lawn. It also acts as a protective layer, shielding the crowns of the grass plants from the sun and preserving moisture. However, whilst a layer of thatch of approximately 1.2 cm (1/2 in) is good for the lawn, excessive thatch can cause the lawn to thin, and so needs to be removed.

Whilst aeration may be carried by simply inserting a garden fork into the soil, there are also a number of purpose-built tools that will remove thatch and aerate the soil with much less effort.

Scarifying Rake

This rake features a series of rigid, sharp tines that removes thatch and debris and cuts into the turf itself. Many models have a head that swings back and forth to help the rake glide over the lawn when pushed, and bite into the lawn when pulled backwards. Alternatively, there are versions available with wheels on either side of the head, which makes the rake less heavy and tiring to use.

Hollow Tine Aerator

These manual or powered machines punch even holes in the surface of the lawn, removing a core of soil from the turf to aerate the soil. Manual aerators are simply pushed into the ground using your foot, in the same way as using a garden fork. Some versions include coil springs to provide automatic ejection of the implement from the lawn and a collecting box for the soil plugs. Petrol-powered models require far less effort to use and may be hired from most tool shops. These powerful machines can penetrate the turf relatively deeply, helping to promote new, healthy growth.

Star Wheeled Slitter

This machine features a large number of flat, sharp tines fitted onto a roller that may be pushed across the turf. The best results are obtained when the lawn is damp as the tines will penetrate more deeply into the lawn. However, in drier conditions, effective aeration can be achieved by applying greater pressure on the handle.

In our section on Lawns, we take a further look at aerating turf, with advice and information on the four major methods: scarifying, slitting, spiking and hollow-tining (coring).