Thank you for writing about violets, Dave.
Throughout our dry, full and partial shade, Viola labradorica has made the most enchanting "weed", an answer to blue23rose's quote, "May all your weeds be wildflowers."
Aspenhill, thank you for mentioning Viola waterii 'Silver Gem'. I looked it up and it looks like it might be another viola treasure to add to my garden.
Having said the foregoing, I used to think I could not grow Viola cornuta, because it fried in our summers. However, through a happy accident, I have discovered I can plant out plants of it from November into January (although October would be best), and it will bloom during winter into May any time the temperature rises. Who knew a flower balking at summer heat in our z7 garden would make such a gorgeous winter flower?
Viola is a huge genus - lots to discover, imho.