Answer: In my experience, no plant can compete with the grass from the lawn, so the best answer for that is to keep the grass away from the edge of the bed. You can dig it out by hand to make a cut edge, use a weed flame tool, edge, or place weed barrier fabric or black plastic under the rock edging to keep the grass out.
There are several things you can do to stop erosion from the beds. A few inches of shredded bark mulch will help keep the soil in place and will also work itself into the niches between the rocks. You can also sprinkle smaller pebbles into the gaps. Spreading, trailing, and creeping plants such as semperivums (hens and chicks), creeping thyme, creeping phlox, achillea millefolium (thread-leafed yarrow), and assorted varieties of sedum can also help. Before planting, make sure there's enough soil between the rocks for them to root properly.You will find, however, that they may need to be controlled over time or they will cover up the rocks. Finally, once the soil has settled you should find that any erosion slows considerably.
Q&A Library Searching Tips