On Monday, 23 September 2019 02:08:57 UTC+1, Bill Wright wrote:
Along a hedge I have a group of five forty-year-old laylandii. Three
have died, probably because they were over-run by ivy. I'm going to pull
them out. But what can I put in their place? I want something fast
growing.

Willow. Can grow 5 ft in four months.

https://www.rhs.org.uk/advice/profile?PID=588

Not sure if they will co-exist with leylandii.

Owain