helping vinca minor to spread faster
I've just finished planting over 500 vinca minor plants on a sloped area. Some of the area is bare in between the plants, but some of the area I left in grass as the slope is steep (erosion), but used something like Round Up to kill the grass. Then I weed-whacked the dead grass to almost nothing before planting the vinca minor. I realize there will be more grass/weeds that will come up. Is there a way to help the vinca to fill in faster, such as maybe putting some soil over part of the runners as they grow out from the plant?