Amsonia illustris Woods. - Blue Star

Amsonia illustris plant

Family - Apocynaceae

Stems - To -1m tall, erect to ascending, simple or branching near apex, glabrous, glaucous, herbaceous, from thick woody roots, with milky sap.

Amsonia illustris stem

Amsonia illustris sapSap of stem.

Leaves - Alternate, short-petiolate, (becoming sessile below). Petioles to -1cm long. Blades lanceolate to linear-lanceolate, acuminate at apex, to 2cm broad, 12cm long, sparse villous below, shiny green and glabrous above(or with sparse pubescence on midrib).

Amsonia illustris leaves

Inflorescence - Dense terminal cymes which as a whole are cylindrical to subpyramidal in shape. Entire inflorescence to +/-15cm tall.

Flowers - Corolla light blue-purple, 5-lobed, with dense multicellular intertwined hairs at summit internally, with dense retrorse pubescence below point of filament attachment. Corolla tube to 7mm long, glabrous near base externally, pubescent to villous in upper half. Lobes to 9mm long, 3mm broad, narrowly oblong to linear-lanceolate. Stamens 5, alternating with corolla lobes, adnate to corolla tube near apex. Filaments .6mm long. Anthers yellow-orange, -1mm long. Style glabrous, 5mm long. Stigma capitate, winged at base. Carpels 2. Calyx tube to 1mm long, 5-lobed, sparse pubescent. Lobes subequal, to 1.5mm long, slightly scarious margined, acute, pubescent. Follicles to 12cm long, many seeded, drooping at maturity.

Amsonia illustris calyxCalyx and corolla tube.

Amsonia illustris flower

Flowering - April - May.

Habitat - Rocky ground along bluffs and streambanks, gravel bars.

Origin - Native to U.S.

Other info. - This plant is quite striking when in flower and is becoming popular in cultivation. The shiny green leaves and dense flower clusters are very attractive. Another species, A. tabernaemontana Walt., looks similar but has dull leaves which are more broad than A. illustris, loose flower clusters, and calices which are glabrous. You can view this plant in this same section of this website.

Photographs taken at Schumaker Park, Jackson County, MO., 5-12-00, and in Ripley County, MO., 5-15-04.