What are some of the favorite fall perennials for garden designers?  Here's a few landscape ideas...

Schizachyrium scoparium / Little Bluestem. "Turns acres of prairie glistening silver in autumn" according to BBG publications. The arching plumes (or seedbeds) are silver; the thin, graceful stalks of the grass begin as blue-green, then transition through tawny colors of gold, orange, red.

Aster oblongifolius 'Raydon's Favorite'.  Blue-violet daisy-ish flowers with cheerful yellow centers bloom from September until frost.  The foliage is aromatic and the flowering is prolific.  If you give it "the Chelsea chop" earlier in the year (May/June), expect a tighter and shorter plant. 

Sedum 'Matrona'.  A clump forming perennial with pale pink umbels from August to October atop burgundy stems and gray-green succulent leaves.  Flower heads are persistent and turn a russet tan color in fall.

Actaea simplex 'atropurpurea' / Black Cohosh or Bugbane.  Its dark hues makes a wonderful backdrop for colorful foliage and flowering shade plants... perfect for a new york city landscape designer that works within a shady, urban environment. In fall, fragrant, cream-colored flowers appear on tall, wandlike stems. 

Anemone hupehensis, A. xhybrida, A. tomentosa /Windflower.  Dark green leaves which are softly pubescent  on tri-parted wiry stems that flow in the breeze. Atop are the 2-3" flowers that range from pure, virginal white to dark pink and purple. These are true fall bloomers