Last summer I was looking for plants to butt up against the rockwall in our middle terrace garden bed and stumbled across a new-to-me plant Polygala myrtifolia (Myrtle-leaf milkwort).
There was a huge display of them at my favourite nursery, and several varieties and plant sizes were on offer, many of which seemed reasonably priced for a "hmmmm, will this work in our conditions?" kind of buy.
Cut to the end of a long, cold winter with six snowfalls and many many deep frosts... The Polygalas all look wonderful! They flowered all winter long, and have only recently dropped their purple pretties. The remained green and lush, and truly I couldn't be happier with the choice.
When we were filling a new bed in autumn I chose to include another Polygala variety, the Little Bibi (which I am fairly sure is a PBRed dwarf variety of the same myrtifolia). I'm not sure that it will work as well in that spot, but I hope to be proven wrong.