Thatch is a build up of dead organic matter laying on the soil surface. Thatch is a natural occurrence as old grass stems die and are replaced by new ones. Bacteria in the soil digest the thatch breaking it down into nutrients for other plants. In severe cases of heavy thatch the bacteria cannot digest all the organic matter and the thatch builds up and forms a fibrous layer on the soil surface. This layer acts like blotting paper preventing the flow of moisture, oxygen and carbon dioxide to and from the grass roots.
It is vital that thatch is not allowed to build up as it can have a disastrous effect on any lawn weakening the grass, encouraging moss and diseases. Scarifying is the physical process of removing thatch from the soil surface. It used to be carried out by using a wire rake. Pitch Perfect Lawns have powered machines which scarify far more comprehensively and are far more efficient than raking. Several vertical metal blades revolve at high speed around a shaft and dig into the ground as the machine is pushed along the lawn. The blades can be set at various heights from the surface and consequently take out various amounts of thatch etc. As well as removing thatch and dead moss the blades also prune the shoots of the grass plant encouraging stronger growth.