Thatch is a natural accumulation of dead grass that is broken down over time by microbes in the soil. The problem is that this can sometimes build up too fast for the natural organic processes to break it down. This is when dethatching your lawn is important, because if left for too long, it can form a barrier that prevents air and moisture to reach the grass.
You should generally think about dethatching your lawn when the thatch has reached a depth of about 1.5cm, but it’s only really beneficial for warm season grasses, such as Buffalo, Couch, Zoysia or Kikuyu that have rhizomes and can recover quickly from the stress of dethatching.
Cold season grasses that don’t have rhizomes, can often recover from dethatching when a manual rake is used, but can be scalped and may never recover if other methods, such as low mowing, lawn coring, and verti-mowing are used instead.
Using a rake for dethatching: If your thatch is around 1cm deep and your lawn is not too large, you might find that you can get away with using a long-tined rake to remove the thatch. This is the least harmful way to dethatch a lawn and you can purchase special rakes that have long tines designed specifically to remove thatch from lawns.
Low cut mowing: As its name implies, low cut mowing is when you mow the lawn at a very low height, much lower than normal. With this method, you are aiming to mow the grass so low that you actually remove the thatch. You might achieve this in one mow or you might need to follow up with additional mows, lowering the height of the blades each time. This method is really slow going and hard work, producing a lot of waste matter that needs to be taken to the tip.
Lawn coring: For this method, you need to hire a lawn coring machine that punches out plugs or cores of soil, thatch, and grass as you move it across the lawn. The result is a lawn covered in hundreds of little holes and is generally used to aerate the soil, but has a side effect of removing some thatch as well. If your soil needs to be aerated and dethatched, lawn coring might be suitable, but with a heavily thatched lawn, it might be best to use one of the other methods. Lawn coring can be another method used for dethatching cool season grasses without rhizomes because they also benefit from aeration as well.
Verti-mowing: This is actually, the best method for dethatching your lawn for two good reasons. The first is that it is less labour intensive than the other methods, which is always good! The second reason is that it just does the job more effectively than the other methods. Vertimowing involves using a machine that removes the thatch and the grass, leaving the lawn to regenerate from the rhizomes. As you can imagine, a lawn without rhizome growth would simply die if this method was used for dethatching. Another point is that verti-mowing produces a lot of waste, even more than low cut mowing. Most people hire in the experts at this point as it creates a lot of dust in the air and most home-owners are happy to leave this job to someone else!
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