Viola odorata "Carol Lockton" was discovered as a chance seedling beside "Opera" (see below) at Groves Nursery in the UK and exhibited internationally in 2007.  It is a heavy bloomer and a vigorous grower.  Its fragrant blooms are a beautiful mid-blue.  "Carol Lockton" couldn't be any lovelier if she tried.  (Groves Nursery, UK, ~2007)  Zones 4-9.