Bar Harbor hugs the ground at 9 to 12 inches and spreads 5 to 6 feet, forming a dense blue-green mat that holds a slope without any help. Juniperus horizontalis 'Bar Harbor' grows in full sun to part sun, hardy from Zone 3 through Zone 8.
The foliage takes on a purple cast in cold weather, so the color shifts through the year rather than staying flat green.
This selection came from the coast of Maine, and salt tolerance is what it brings. It handles salt spray, sandy soil, and wind about as well as any evergreen groundcover available, which is why it turns up on dune plantings and coastal banks.
It wants full sun and sharp drainage, and wet ground is what kills it. Deer leave it alone. Space 4 feet apart for coverage. Keep it away from apples, crabapples, and hawthorns, since junipers host cedar-apple rust.