Amsonia hubrichtii #1 (Thread-leaf Blue Star)

Thread-leaf Blue Star is an uncommon perennial native to the Ouachita Mountains of Arkansas and is most magnificent when planted in masses, where its fine foliage can sway in the breeze. Purple buds open to sky blue flowers in April or May, fading to whitish in the sun. The flowers attract numerous pollinators with their nectar, especially butterflies. It is not picky about soil type but requires well-drained sites and may flop over in part shade. The spectacular, golden fall color is best when planted in full sun and is a striking feature in the autumn perennial garden.

As a member of the Dogbane family (Apocynaceae), its sap produces a milky latex that deters browsing by deer or rabbits. The Snowberry Clearwing moth hosts on members of this family, though a specific host relationship has not been documented since this plant is relatively rare outside its native range.

Sources:
Herbaceous Perennial Plants by Allan M. Armitage
Missouri Botanical Garden
Lady Bird Johnson Wildflower Center