Some species of grass produce more horizontal growth than others and this can build up to a point where it needs to be removed to allow healthy growth.  Scarifying is really a pruning process and is done using vertical blades that cut into the top of the turf mat.

The frequency of scarifying necessary depends upon the type of turf, and the maintenance regime. For example, a turf containing ryegrass needs very little, if any, scarifying because of the tufted growth characteristic of the ryegrass.  A turf containing no ryegrass is likely to need scarifying at least every two years because of the lateral growth of bents, fescues, and smooth stalked meadow grass.  In addition, if the turf is regularly fertilised and watered the growth rate will increase, resulting in a faster build-up of the turf mat.  In this situation lawns will benefit from scarifying every year, preferably during the early autumn.

Scarifying involves raking vigorously with a spring-tined or sharp-toothed rake, pushing it well down to pull out the dead grass or moss and break stem of creeping grasses. Scarify two weeks after using a moss-killer to remove the dead moss.