Schwab GmbH, Marktführer für Rollrasen in Deutschland

The scarifying myth: A dangerous fairy story

„Handsoff from scarifying“: We are absolutely serious about this warning! Even though some garden enthusiasts will be suprised about it. Under professionell view the scarifying myth ist a pure fairy story, and even a very dangerous, because scarifying your turf is much more damaging than beneficial.

Scarifying is the term for the vertical cleaving of the grass grain for dethatching. This applies primarily to the professional sector, in order to make football fields and golf courses, stadiums and arenas playable in all types of weather. The quality of the grass grain is secondary.

In order to achieve this durability and water permeability, the turf base course, in other words the layer in which the grass grows, must primarily consist of sand in order to achieve maximal water permeability with the best possible shearing resistance. Today, a turf base course is normally comprised of 90% sand and 10% sandy top soil. This soil is lean and adversarial to plant growth, but has maximum water permeability. In order to allow good turf to prosper on such soil, specialists and special care measures are required.

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Due to the lack of soil organisms, natural thatching occurs, arising from the swath left behind, and must be removed by means of currying and scarifying. By rolling the example lawn surfaces with cleats, green grasses are pressed into the soil and partially anaerobically decomposed. This can cause a hard, water-repellent thatch which hinders water permeability. Therefore, thatch in the professional sector is undesired and must be removed by violent means in which the grass grain is always damaged. This is a measure used by the professional which comprises four steps: scarifying, sanding, reseeding and fertilising. Scarifying in order to remove the thatch, sanding to increase water permeability and to “thin out” the remaining thatch, re-sowing to repair the battered grass grain and fertilisation to strengthen the remaining grass.

In private gardens water permeability is not the highest aim, rather a beautiful lawn. On good garden soils there is never more than a loose a thatch of more than one centimetre, which is even important for the grass grain. Therefore, thatch is not the problem. Moss is frequently the problem in private lawns. However, moss has nothing to do with thatch. Moss is an indicator of nitrogen deficiency. Moss only grows when there is too little fertilisation and the soil is poor in nutrients. This is usually in the crown area of trees and in the area of hedges, which is why the rumour that moss grows from shade and moist ground persists. In reality, the nutrients in these areas are only consumed more quickly by the flat haustoria of trees and bushes and there is usually simply a need for more fertiliser in these areas. Of course, fertiliser, especially organic fertiliser, does not take as well in shaded areas. However this is not causal; it is merely an aggravating factor. Therefore moss does not grow where sufficient fertilising has taken place and disappears as soon as nitrogen is added.

What happens when a moss-covered lawn is scarified in order to manually remove the moss? On the one hand, grass plants that are stressed and hungry, as well as injured are destroyed along with the leaf and root mass. On the other hand, “landing strips” are created for the germination of weeds in the spring, especially for dandelion which is already in flight during the spring. The more often scarification is performed, the more the grass grain is injured, the more weed growth occurs and the more quickly the lawn takes on an unsightly appearance.