2. Amsonia illustris Woodson (shining blue star)

Pl. 215 c–e; Map 896

Stems 60–100 cm long, 5–10 mm in diameter at the base, glabrous, the branches elongating to 10–35 cm after flowering. Leaves alternate or appearing subopposite at some nodes, short-petiolate. Leaf blades mostly 4–12 cm long, 1.5–3.0 cm wide, those of the main stem leaves narrowly lanceolate to lanceolate, the upper surface shiny, the undersurface pale green, glabrous or sparsely hairy along the main veins, occasionally somewhat glaucous. Inflorescences loose, terminal and sometimes also subterminal clusters, 7–12 cm long at flowering, barely surpassing the branches and foliage. Flower stalks 2–8 mm long. Calyces sparsely hairy, the lobes 1–2 mm long, narrowly to less commonly broadly triangular. Corollas densely hairy internally, sparsely hairy externally, the tube 6–8 mm long, about 1.5 mm wide at base, the throat 3.0–3.5 mm wide, the lobes 5–10 mm long, 1.5–3.0 mm wide. Fruits 7–15 cm long, spreading to pendulous at maturity and positioned among the leaves, slightly constricted between the seeds and sometimes breaking between them. Seeds 6–9 mm long, 2–3 mm wide, the surface usually with low, corky ridges and tubercles, dark brown. 2n=22. April–June.

Scattered in the southern half of the state, mostly in the Ozark Division (Missouri and Arkansas west to Kansas, Oklahoma, and Texas). Gravelly banks of streams and rivers, ledges and tops of bluffs, and occasionally glades and openings of dry upland forests.

In general, this species is recognized by the lustrous upper leaf surface, sparsely hairy calyx, and constricted follicles that are drooping at maturity. It is closely related to A. tabernaemontana and could be viewed as a variety of that species. However, the distinctive leaf and flower characters along with the tendency toward a streamside habitat support recognition of this taxon at the species level (Woodson, 1929).