gardengus, that is a lovely plant! I searched up and down to try to figure out its identity, and have nothing absolutely conclusive, but my best guess is maybe a dwarf form of
Silene dioica (of which there are some in cultivation according to James Jones'
Lychnis and Silene in the Garden).
Here's an entry for
Silene dioica which seems to hit the mark, from what I can see in comparison to your photo:
http://www.terrain.net.nz/frie...
