Scarifying lawns (dethatching lawns) to remove thatch and moss
A picture of the blades on a lawn scarifier. These blades penetrate into the turf and remove large quantities of thatch and moss from the lawn.
What is lawn scarifying and dethatching
Over a period of time lawns suffer a build up of organic matter adding to what is called the thatch layer. This can be caused by grass clippings, decaying stems and shoots, in fact any dead or decaying organic matter.
If this build up is allowed to continue without any removal program such as scarifying or dethatching, the thatch build up will become too excessive and have an adverse affect on the health of the lawn.
For problems associated with excessive thatch please visit the thatch section on this website.
Scarifying lawns and turf areas is the task of removing organic matter by using a powered machine with spinning vertical blades, or alternatively a hand rake, this process is also known as dethatching. Both of these methods penetrate into this layer below the grass and remove the organic matter that contributes to the thatch layer
Types of scarifiers and lawn rakes
Powered Scarifier and Lawn Rakes: These machines are ideal for scarifying lawns or dethatching lawns that cover a large area, or any lawn with a serious thatch problem. In fact if you have a serious problem with thatch build up, powered machines remove larger amounts of thatch than a hand rake or a sweeper.
They can be used any time during the growing season as the depth can be easily adjusted. e.g. a light scarification can be beneficial to eliminated any lateral growth to maintain a thick sward. Alternatively a deep setting would be used to remove a lot of thatch during an autumn renovation program.
A powered scarifier or dethatcher is particularly effective when used in conjunction with hollow tining for removing large amounts of thatch.
Springbok or Spring tine Rake: These rakes help to discourage any lateral growth and rake out any dead material in the base of the sward. A spring tine rake is ideal for small lawns or where thatch is not a major problem. Hand rakes are not really suitable for large lawns as it can be back breaking work doing it by hand.
A spring tine rake is ideal for removing moss from the lawn in the spring time after a moss killer treatment. It leaves a nice seed bed, ideal for overseeding any bare or thin areas after the moss has been removed.
A spring tine rake would also be beneficial in preventing thatch build up with regular use before mowing. This stands up any grass to prevent lateral growth and has the added benefit of removing the seed heads of any undesirable grasses such as annual meadow grass.
Brushing: There are two types of brushing, either with a mechanical sweeper or a hand held brush. However both of then are useful for cleaning up the sward for any debris or litter such as leaves, dead grass or worm-casts which may contribute to thatch build up. A brush is also ideal for use before mowing to stand the grass and seed heads up to prevent lateral growth etc.
These three methods are all effective ways of preventing and removing thatch. If you have a serious problem with thatch, a scarifier will be the most effective way of removing it. Raking and brushing are basically refinements of scarifying and are ideal for preventing the build up of thatch and keeping the sward clean.
When to scarify your lawn
All of these scarifying operations are best carried out during the growing season during periods of strong growth (avoid periods of drought) as the grass needs sufficient time to recover afterwards. Deep scarification is commonly carried out during the early autumn while there is still enough growth left for it to make a full recovery. It would normally be undertaken before overseeding and top dressing as part of the Autumn renovation program.
Deep scarifying, again could also be carried out during the spring after any moss control, prior to overseeding and top dressing. During the summer frequent light scarifying or raking and brushing could take place at every 2 - 4 weeks. This would help prevent any lateral growth and remove any seed heads from undesirable grasses or weeds to prevent them spreading.
Always make sure that there is sufficient growth for recovery after any deep scarification operation. You would not want to go into the winter months with a thin sward that has not had sufficient time to recover. This would be an open invitation for moss invasion or disease problems.
Again don't scarify too early in spring time when it is still cold, it is better to wait until the temperatures rise to encourage grass growth for a quick recovery.