Tiger Eyes Sumac is an incredibly tough plant that is perfect for this situation. It does great in rocky soil, will colonize and, in time, help cover the area. Candy Coralberry is another easy to care for plant that does well in rocky sites. Though I haven’t tried it, I know some people who use vines as groundcovers. It would be fun to try that with Atomic Red Trumpet Vine, Autumn Revolution Bittersweet or Honeybelle Honeysuckle.
Thanks for writing!