Once again thanks are due to local plant enthusiast Alan Tracey for sharing one of his photographs with us from his trip along the Dempster Highway a couple years ago--quite handy for a "Plants of the North" series. You can read about Alan's trip in the Spring 2009 Bulletin of the Alpine Garden Club of British Columbia (and, as a note, to make up for the bandwidth of downloading the large-ish PDFs, local readers should consider attending the AGC-BC's shows or sales).
One of the truest "plants of the north", Saxifraga oppositifolia (purple saxifrage) is "one of the four species of plants known from the northernmost botanical locality on earth, that is Lockwood Island, 83°24'N, on the north coast of Greenland", according to the Saxifraga oppositifolia entry from Flora of the Canadian Arctic Archipelago. Not restricted to Canada and Greenland, the species has circumboreal distribution. In the more southern parts of its range, it is an alpine plant; locally, it can be found on Mt. Cheam, blooming in late June (and you'll be hiking through snow to see it).
Saxifraga oppositifolia is one of a number of species that are part of Canada's PlantWatch, a "volunteer monitoring program designed to help identify ecological changes that may be affecting our environment". The idea is that citizen scientists from across the country will monitor particular species and record phenological data (e.g., first bloom, peak bloom, fruit ripe, etc.), and this will help build a dataset to identify long-term trends (particularly in relation to climate change). At a local plant group meeting, Saxifraga oppositifolia's inclusion as one of the species on the list for British Columbia was met with some interest (as noted above, it is a fair hike to go see the nearest population, not to mention the drive). When taken in the context that PlantWatch is a cross-Canada monitoring program (and that Saxifraga oppositifolia is the territorial flower of Nunavut and far more readily seen in the north), its inclusion is more understandable.
For additional photographs of Saxifraga oppositifolia, including some cultivars, see SaxBase: Saxifraga oppositifolia.