Mike Barnes wrote

How to kill a buddleia?

It's growing in the 8" gap between the greenhouse and the boundary fence
(sheep netting). It's distorted the greenhouse frame, breaking one of the
panes. I've hacked back the buddleia and replaced the pane.

Knowing that buddleias like a good prune I'm assuming it's likely to carry
on growing and cause more damage, so I'd like to kill it. First thoughts
are chemical, but I don't know what to use and how to apply it.

Ideas?

I apply neat Roundup to the cut surfaces and it kills everything I have done
that with.