Triosteum aurantiacum var. illinoense (Wiegand) E. J. Palmer & Steyerm.
Family: Caprifoliaceae
Illinois horse-gentian
Triosteum aurantiacum var. illinoense image
Morton Arboretum  
Perennial herb to 1.3 m tall Stem: upright, shaggy-hairy. The hairs are non-glandular and up to 3 mm long. Leaves: opposite, stalkless, 10 - 30 cm long, 4 - 15 cm wide, broadly elliptic with narrowing base and pointed tip, sparsely hairy above, densely soft-hairy beneath. Bases of paired leaves fused (connate), and seemingly pierced by stem. Only up to two pairs of leaves might be connate at the base. Flowers: one to four, in upper leaf axils. Sepals five, 1 - 1.8 cm long, about 1.5 mm wide, linear, elongate, finely hairy (often glandular) on the back and along the margins. Corolla unequally five-lobed, purplish red, to 2 cm long, about 2 mm wide, tubular or bell-shaped, base swollen, crisp-hairy. Stamens five. Style within the corolla. Fruit: berry-like (drupe), dull yellowish orange, hairy, dry, with persistent five-lobed calyx. There are three oblong stones inside each drupe.

Similar species: The variety aurantiacum has some glandular hairs on its stems, and the hairs only grow to 1.5 mm long. The similar Triosteum angustifolium has bristly-hairy stems and hairless sepals with bristly margins. Triosteum perfoliatum is also similar but differs by having styles exserted from the corolla and at least three or more pairs of leaves connate at the base.

Flowering: mid-May to early June

Habitat and ecology: Locally frequent in open, often mesic, woodlands.

Occurence in the Chicago region: native

Etymology: Triosteum comes from the Greek words treis, meaning three, and osteon, meaning "a bone" (in reference to the three stones inside the fruit). Aurantiacum means orange-colored. Illinoense means "of or from Illinois."

Author: The Morton Arboretum

From Flora of Indiana (1940) by Charles C. Deam
This variety occurs throughout the state. Nearly all of our specimens are from rocky, wooded slopes bordering streams. A few are from dry woods. The pubescence of the fruit, stem, and leaves is longer than that in the species.