Lyn, the vinca sounds like it might be ideal, if it's keeping the star thistle from invading an area. Does it re-root itself as it grows? If it does, it would be great at stabilizing the soil, which would be an added bonus. My husband pulled everything off of part of one slope, mostly star thistle, between the lawn and the driveway and now it's just bare dirt. We know that the seeds will grow this winter, but we hope to get it all out of there in a year or two. We're planting wildflowers there next year, because it would be so pretty, but I doubt that will last forever, since they won't really stabilize the ground much. We live in a river canyon, so some of our property is very steep! We're removing all of the star thistle that we can, but with 12 1/2 acres, some of it close to vertical, we'll never get rid of all of it. But, we need things that can compete to keep in under control. At the bottom of the slope between the lawn and the driveway is a row of pine trees, and that is the only place that there is any shade. Sounds like it would be a bad idea to plant the vinca there, as it would invade the lawn eventually. But, I have other spots where it would be great, and could grow all it wants!
