Perennial herb to 1.3 m tall Stem: upright, sparsely hairy, with hairs up to 1.5 mm long. Some of the shorter hairs are glandular. Leaves: opposite, stalkless, 10 - 30 cm long, 4 - 15 cm wide, broadly elliptic with narrowing base and pointed tip, sparsely glandular-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 illinoense lacks glandular hairs on its stems, and the hairs grow to 3 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: late April to late 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.
Author: The Morton Arboretum
From Flora of Indiana (1940) by Charles C. Deam
Infrequent possibly throughout the state. It is generally found in rather open, dry woods and more rarely in moist, sandy places in a prairie habitat. Wiegand places this species as a variety of the preceding one [Triosetum perfoliatum] on the basis that there are intergrading plants and some plants of the nonperfoliate group are sometimes perfoliate and sometimes the pubescence characters are not constant. It has been observed that, as is shown in Bicknell's description, the leaves of T. aurantiacum are sometimes perfoliate but it is true only of the upper ones, not the middle or principal leaves, while in T. perftoliaturn, it is the middle leaves which are perfoliate and if there is any difference in the leaves, it is the upper ones which are narrowed. The fruit characters, however, their color, shape, and pubescence, the time of flowering and maturing of fruit, and various other combinations of characters are sufficient to separate the two without depending upon the types of leaves although they are helpful when understood.