Which season is best?
For the most part, it’s best to scarify your lawn twice a year. Once at the beginning of the mowing season around March, and again at the end of September before the cold of winter sets in.
This ensures that a thin layer of thatch is left for the entire year. Avoid scarifying in the summer or winter months.
If you have shady areas in your garden, it is best to scarify only once a year in the spring to allow for regrowth. Scarifying in autumn will thin the grass without allowing it to grow, potentially making thatch much worse.
How to prepare your lawn for scarifying
Short grass is ideal for scarifying your lawn. Longer grass is not impossible, but it requires more time, effort and patience to achieve. You should cut the grass with a lawn mower a couple of weeks before you plan to scarify the grass. This will ensure the grass is a suitable length to dethatch and it will minimise the stress on the grass.
Which weather conditions are best?
Whichever season you choose to scarify in, you will need plenty of sun to allow the grass to grow strongly afterwards. However, you should avoid scarifying your lawn in extremely dry conditions. Similarly, avoid scarifying the lawn in cold or overly damp conditions.