I have just planted 2600 bare root vinca minor plants in a shady area that used to have very sad, unhappy grass. After killing (or so I thought) the grass with Roundup, I skimmed the top layer of dirt/dead grass off, then added topsoil and leafgrow. I also used Plant Starter liquid on each root and in each hole. The vinca were planted 4-6 inches apart, then mulched with about an inch of pine bark,and they are doing extremely well, if I do say so myself! Very green and healthy looking.

The problem is that now, with all of the soil preparation I did, and the careful watering I am doing, there is new grass growing up between and around the vinca plants, I suppose from ungerminated seeds that had been present in the dirt from all my earlier efforts to make grass grow.

Will the new grass die over the winter, and will the vinca take it over when it spreads? I am looking for a carpet of vinca type effect.