Catmint (Nepeta mussinii or Nepeta racemosa) is a mint family perennial shrub that makes an excellent ground cover for rough, low water/low fertility soil conditions.
Related, but distinct from Catnip (Nepeta cataria) – although the common names are often used interchangeably for either plant. Differentiating features of Catmint are the leaves (smaller than Catnip) and flowers (purple, whereas Catnip has white). Kitties love both.
Frost hardy to zone 4. Spring sown seeds will form small shrubs and flowers in their first year, overwinter and encompassing 3-4 feet in area at maturity. Can grow bigger/spread farther with more accommodating soil conditions (more water and fertility).