String Theory Bluestar - Amsonia

String Theory is a compact selection of threadleaf bluestar, with light periwinkle-blue star flowers above narrow dark-green leaves. It keeps a dense, upright outline, then turns golden-orange in fall ([Walters Gardens cultivar profile](https://www.waltersgardens.com/variety.php?ID=AMSSY)). ## Landscape Use Use it in sunny perennial borders, grouped plantings, containers, or as a small specimen. Walters Gardens lists mature dimensions of 24–30 inches tall by 32–36 inches wide and hardiness in USDA zones 4–9. The compact size distinguishes it from taller, more open *A. hubrichtii*. The cultivar is a Walters Gardens introduction marketed through Proven Winners. Its US plant patent is USPP34419P2, granted July 12, 2022 ([patent record](https://patents.google.com/patent/USPP34419)). ## Seasonal Interest Flowers appear in late spring, with the patent describing a display that typically lasts about three to four weeks. Dense, linear foliage remains dark green through summer before turning golden-orange in fall. Walters Gardens also notes deer resistance and tolerance of heat and humidity. ## Siting Plant in full sun or part shade. Provide average garden soil with drainage and regular moisture while the plant establishes; avoid rich, deeply shaded sites where Amsonia can become loose or floppy. Iowa State Extension notes that the parent species *A. hubrichtii* generally prefers drier soil than *A. tabernaemontana*, so do not keep the root zone saturated. ## Maintenance This perennial needs little routine care. After flowering, cut stems back if the clump becomes floppy or if a shorter outline is wanted; otherwise, let the foliage provide summer texture and fall color. Remove dormant stems near the ground in late winter or early spring without damaging emerging shoots.