Yes they are perennial here in tennessee, even in my zone 6b.

Plant them now!! Won't be long till they are blooming, I had my first buttercup bloom today. While my neighbors and others around town have been blooming for a week.

They reseed heavily if allowed, and they shoot the seeds everywhere. LOL, I brought a seed pod in that hadn't shot all of the seeds out and I kept hearing this noise. I thought I had a mouse. Well I went looking for this mouse. Come to find out it was the viola seeds popping out of the pod, lol. I put the pod and the seeds I could find in a paper sack, lol, yes this only increased the sound!!

Once they get established in your yard, they can really start taking over. It's taken me a few years to weed them out of my beds.

This is with me collecting my viola seed, dern boogers popped before I could collect them!! I have thinned my viola out quite a bit actually I would say I took out 75%. The green seedlings are strictly viola.

Oh my. Well, where I plan on putting these, that will be just FINE! My front yard is very small, and in the shade of a huge old maple tree. Grass simply won't grow there, but I already have a number of violets. A solid carpet of violas would be okay. (*grin*)