Two little-known facts about violets.
First, they're delicious to eat. From starchy root to confectionary flower, every single part, sweet or scentless, should have devotees in every place they grow. It should be cultivated, and its zesty, assertive leaves put onto NYU's student menu as salad, soup or sauce. Considered a regional specialty of Spain and Italy, it merits in Madrid, a directed boutique, La Violeta. Over here, it should be obsessively bred like hemp for its oils, while the shyer native species put on a conservation list, so they can propagate their mongrel kind. Violet heads can be candied, iced, preserved in vinegar or jam, dried as scented ink or natural food coloring, used to flavor vodka, or enjoyed on their own, with watercress and Belgian endive, or eaten from the hand (violet fighting, as in hooking violets, pulling, and the victor eating the loser, is very fun). Violet flavor ought to be something that you can get at the local grocery (next to the rose water, and ...oh, I'm getting carried away). In short, if you find violets in your yard, don't consider them "weeds". Eat some, and transplant the rest someplace safe. They will make lots of leaves in between times.
Second, they're a trickster. Every bite of Violet will overload your nose with a local anesthetic, ionone, which will paralyze your olfactories for anything from a few minutes to two hours. Hence, the coinage "iocaine powder", which played so large a part in "The Princess Bride".
Hope I've made some things clear.