I built a rock terrace several years ago. The rocks were laid on a 3" bed of sand. Now, years later, ivy & vinca are trying to take over via the edges of the rock terrace. I have now dug the vines out around the edges but need a long term way to keep the vines out. Does anyone know of a herbiside which I can apply around the edges which will not travel through the stems into the surrounding vines ( which I want to keep healthy). I am a 65 yr. Old female gardener trying to find easier ways to manage my garden.