The thread-leaf blue star (Amsonia hubrichtii) is not hardy in all of the north (USDA zone 5 or -10 to -20 degrees F average winter low). Where it does grow this less common perennial, native to the mountains of Arkansas, provides a mound of powdery blue, star-shaped flowers in early summer in the north. Plants form a mound 2 to 3 feet tall and wide. It provides a fine feathery texture with its thread-like leaves that turn gold in fall.
Like other bluestars, this one grows best in full sun in the north, and moist but well-drained soil. It will tolerate dry soil once established. Also it will tolerate some shade, but may flop and have less showy fall color. It is best massed in borders, by itself, native plant gardens, or individually in rock gardens. It combines well with blue woodland phlox (Phlox divaricata).
Recent Perennial Plant of the Year winners that you might consider too include the golden Hakone grass and hellebores (both generally hardy to zone 5), 'Rozanne' perennial geranium, 'Walker's Low' catmint, 'Becky' shasta daisy, 'David' garden phlox, and Japanese painted fern. More on these, and other winners, can be found online (www.perennialplant.org).