This diminutive, trailing violet, with
blooms of purple and white, is suited
for warmer climates where it puts on a show from summer well into fall.  In fact, it has bloomed in my greenhouse 12 months of the year, which is very good news for those in the right zones.   Viola hederacea (Australian Violet) isn't too fussy about soil, although I have found it doesn't like soil that is bone dry.  I haven't tried it yet, but this pretty perennial violet might be worthy of a potted plant -  hanging or just sitting on a porch - in cooler climates and then moved inside for winter protection.  Note:  I unintentionally left several pots of this tender trailing violet outside here in Zone 6, and they made it through several heavy frosts, so maybe they are not as tender as one might think.)  Shade.  Zones 8-9.  Quarts.  Temporarily Unavailable.

The attraction of this violet is not only its dainty, bluish/purple blooms but also its deep green/purple foliage.  Viola labradorica is not fussy about soil, although it does prefer it on the moist and well-drained side.  These little gems grow in partial shade from three to five inches high and in Zones 3-8.

Viola odorata "Clive Groves" is another sweetly scented violet with heart-shaped leaves and larger blooms than "Queen Charlotte," with a color not as deep purple.  Zones 3-9.  Quarts.

Viola "odorata" seems like an oxymoron to me.  When one speaks of "odor," the sweet perfume of the scented violet hardly comes to mind.  Perhaps viola "fragrantica" or viola "parfuma" might be more appropriate.  The diminutive blooms of this clump-forming native of Europe and Asia are medium pink with a splash of deep pink in the center.  Protect this violet from heavy freezes with mulch or pine straw if planting outside.  Violets don't like extreme heat, so placement in a place with plenty of shade is a good idea.  For indoor planting, clay pots work best for good root development.  Direct sun is beneficial, as is placement near a window, with nighttime temperatures between 30 and 40 degrees F. to induce and maintain blooms.  Violets may be kept intact by snipping off runners.  For more information about all violets and their care and uses, visit the American Violet Society website.  Zones 5-8.  Quarts.

Viola odorata "Queen Charlotte" grows to about four inches with heart-shaped leaves and dainty deep purple, perfumed blooms.  "Queen Charlotte's" flowers are a tad smaller than those of "Rosina" and "Clive Groves" but they make up for it with their powerful perfume.  Growing information is the same as for "Rosina," above.  Zones 5-8.  Quarts.  (Illustration by Carl Axel Magnus Lindman (1856-1926) from Bilder ur Nordens Flora, from Wiki Commons, and in the public domain.)

I thought that with the word, "neige," in the name of this scented violet (French for "snow), this would be a white bloomer, and it is, sort of.  On the same plant, sometimes the blooms are pure white; other times, like at left, they are pale lavender.  Either way, this violet is lovely, and the heady perfume is ever present.
Zones 5-8.