|I have just put down new sod and left an 18|
|Little Henry Sweetspire has the best fall color. This new compact Sweetspire has pure white flowers that shoot like fireworks in the early summer horizon. Its low mounded, compact stature is perfectly suited for flooding large banks, beds and borders. It grows 24-36 inches tall with equal width.
Woods Dwarf Nandina has firey red colors and produces berries which are attractive to birds. It's a smaller shrub - only 18" high and wide so it would fit the area better. I'd choose Nandina over Sweetspire for the site you describe.
You might also consider Dwarf Yaupon Holly (Ilex vomitoria ?Nana?), Rosemary or Lavender for your border.
Best wishes with your landscape!