When I planned the Magic Garden, I intended to have contrast of silver & white against near black. I already had used heuchera in the garden and they had, generally speaking, grown well. They are native to North America & are more or less evergreen although mine do die back in winter.
I have several Heuchera scattered through the Magic Garden but they are all looking a bit scruffy so I suspect some drastic ‘pruning’ will be required to get the clump forming effect back. I have one very large Heuchera ‘Obsidian’ which is much darker than my others. It is currently in one of the aluminium pots. I may try and split it although I’m wary of spoiling a good specimen. I will though split up the trio that I bought last week as a bargain pot & see what I end up with.