Scarifying reduces the thatch that naturally builds up in your lawn. The grass clippings, dying roots and other organic material that accumulate between the grass and soil is known as thatch. As it decomposes, this layer of material is beneficial in that it provides nutrients to the soil. However, when it gets too thick, thatch can prevent air and water from penetrating the soil, which ultimately causes your grass to die off. A thatch layer of no more than 1/2 inch is healthy for lawns. Scarifying should be done only in the spring or fall when the grass is in peak growing season.
Remove a small square of turf from the lawn that is about 6 inches deep. The thatch is the brown layer of material between the grass blades and the soil. Measure the depth of the thatch. You will need to scarify if it is more than 1/2 inch thick. Replace the piece of turf when finished and tamp it down with your foot. Checking different areas of the lawn this way will give you a better understanding of the overall thatch condition of the lawn.
Cut the lawn as short as possible to make scarifying easier. Remove all the grass clippings. Scarifying with a rake is very physical work, so wear a good pair of gloves to protect your hands. The scarifying rake has sharp, rigid tines designed to cut through the thatch. The tines must be pushed down deep enough to get below the thatch layer but not so deep that they cut the roots of the grass as well. Pull the rake toward you while maintaining firm pressure to keep the tines down. The thatch will be pulled to the surface as you tear through it.
Rake each area several times to remove as much thatch as possible. If grass is being pulled out, it means the tines are cutting through the roots and you should raise the rake slightly. When done correctly, scarifying will pull up a lot of material. Dispose of it in leaf bags. You can also compost the thatch if your lawn is relatively free of weeds.