Heal All (Prunella Vulgaris) - perennial herb in the mint family with purple or white tubular flowers that bloom from June through August & can be grown as ground cover.
 
Growth: Can grow 1 – 2 ft tall.
Light: Prefers partial shade.
Soil: Grows best around woodland edges & meadows.
Hardiness: Able to grow nearly anywhere
Maintenance: Prone to vigorous spreading (like most mints) so some containment might be warranted. To prevent reseeding, trim back after blooming has stopped.
Benefits: Has historically been used medicinally for centuries for a variety of treatments.