Keeping violets out
 

A few years ago I tilled along the length of fence in my backyard. I
didn't fill it front to back with flowers but I mulched pretty good. I
think this is summer 4.

Now, despite multiple cleanings last year and the year before, I have
violets taking over every place there aren't any plants and then some (I
won't even mention the creeping charlie).

I have started to dig everything up again but I'm wondering if I should
lay down dark plastic for a year or so? Or with violets does that not
matter.

I wouldn't mind so much if they stayed to themselves but they are really
not that nice.

TIA,

Diane