Scarifying your lawn is quite an important process, it removes all the thatch and unwanted debris from the base of the grass encouraging new growth once the weather and soil start to warm up.
It can be carried out in spring(March/April) or autumn(September) although it is very weather dependent. After scarifying the grass needs time to recover and if the weather is too cold in autumn it will open it up for being very muddy and so disease prone over the winter period. In March/April if it went really dry and warmed up early.
The ground might dry out too much and the grass not have time to recover and may need watering.
Unless the lawn is really bad once a year is probably enough so getting to know your grass is quite important to know when it would be best to carry out this process and also your local environment and weather conditions.
You can hire a scarifier from a local hire shop. If you have a large lawn this is probably the most economical way to carry out the job. The scarifiers you buy from a DIY store will do a reasonable job but won’t be as thorough as the heavier weight equipment available from the hire shop.
It’s a good idea to cut your grass before you scarify, this means the scarifier has got less work to do to get to the base of the grass, it’s also a good idea to go over it opposite directions just to make sure that you have covered all the area. To help the lawn recover a fertiliser is a good idea afterwards, this will just give the lawn a boost, and speed up its recovery rate.
It is quite a slow process, even with a good machine, to do the job thoroughly takes a lot of time. Then the cleaning up afterwards generates a lot of waste but the lawn will definitely thank you for it in the weeks to come.