I had ants all over my sedum acre and my walkway. I just recently looked for solutions and today put out some ant bait to get rid of them. Can't say it worked yet, but from what I've read it should. All it requires is water, sugar and boric acid (which is a powder bug killer, i picked some up at walgreens for $4). The recipe I read was 1 cup water, 2 cups sugar (put it in the microwave to then mix and dissolve the sugar), and then mix with 2 Tbl boric acid. I put it out by where they are in little water bottle caps. They then find it, come and feed, and take it back to their nest and queen (fingers crossed). Then the whole colony is supposed to die. This will take care of your ant problem, don't know if that's the solution to your vinca issue though.