In article , Peter
writes
I know that you should scarify a lawn in the Autumn or in the Spring,

I wonder where you heard that?
We always thought you should scarify a lawn only when the grass is
growing strongly ie late spring to early autumn - taking into account
local growing conditions!!!!

but
when is it too late, in the Autumn to do this and why.

We never do it before May or after September because that is when the
grass is not growing and can't recover from any damage you cause it in
the scarifying process.

I am able to hire a
scarifier for the end of October.

Don't do it, Peter!
Don't do it until next May at least.
Then after a couple of weeks, give it a feed.
Then repeat the process once every 6 weeks or so through the summer.
--
Jane Ransom in Lancaster.
I won't respond to private emails that are on topic for urg
but if you need to email me for any other reason,
put jandg dot demon dot co dot uk where you see deadspam.com