Hi Sheila! I find Libertia are quite short lived, so yours count as great-grand-daddy Libertias - pretty venerable specimens. By all means tidy them up a bit if you wish, but they may have reached the end of the road. I find they self seed gently so I've never been short of replacements when the older ones go to the great compost heap in the sky.

Thanks for that incredibly quick answer, Beattie! Yes, they self-seed prolifically, but even the babes have gone brown. Think I'll take the older ones out, then see if there are even smaller "seedlings" lying in wait.