Help. I'm confused. I live in SE England and am about to overseed my
lawn. In my Lawn Expert book it says,

"Scarifying - DO NOT USE IN SPRING. Heavy raking which tears into the
grass will damage the lawn. The grass does not produce side-shoots at
this stage and so scarifying will open up the turf and make it
vunerable to weed invasion"

However, on the Johnsons Laws Seed box the instructions for overseeding
say,

"Scarify lawn using a spring tine rake to remove and break up layers of
dead matted grass or thatch"

So which is correct?!