Professor Stefan Buczacki problem solves
Julie Watson, Coalville, Leicestershire
Stefan says: Scarifying is the removal of thatch from a lawn. Thatch is the mass of organic matter, mostly dead straw-like grass stems and leaves, that accumulates at soil level between the living grass of lawn turf. It's a mixture of grass that has died naturally and the clippings that follow lawn mowing and have escaped the mower's grass collector. Left alone it will form a permanent blanket that inhibits the penetration of rainwater and any fertiliser applied to the grass and, in time, it will adversely affect the overall vigour of the lawn.
Thatch can to some extent be removed by using a spring tine lawn rake but I always say this is masochist's work. On anything other than a really small lawn it's desperately tiring and you may see little return for several hours of effort. So some form of powered assistance is needed.
On really large lawns, it could be worth considering a petrol-engine scarifier. Models are available ranging from around £300 to over £2,000, which is a big investment for something you will use once a year at the most, so it may be better to hire one for occasional use.
There's one other petrolengine option; a cylinder lawn mower with interchangeable cartridges. You can remove the cutter blades and insert a scarifier assembly. It sounds great in theory but I've tried one several times over the years and consistently find the engine may be fine for mowing but is just not powerful enough to scarify and grinds to a halt far too readily. For more conventionally-sized lawns therefore, an electric model, either mains or battery-powered, is the
best choice. I always remove the collection box, however, because they fill far too quickly and I'd rather go over the lawn with a wide rake and collect everything afterwards.
My advice is to scarify once a year in the spring. I know many folk recommend autumn scarifying but this leaves the lawn in a frightful mess all winter, whereas in spring, the new grass will come through really quickly.
And finally, do use your scarifier sparingly and go over each part of the lawn just once. There's a temptation, especially with the smaller electric machines, to use it like a carpet sweeper in a backward and forward action. Now that really will make a mess and rip out much of the live grass along with the dead.