Triosteum aurantiacum E. P. Bicknell
Family: Caprifoliaceae
Orange-Fruit Horse-Gentian,  more...
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Morton Arboretum  
Perennial herb to 1.3 m tall Stem: upright, hairy, with hairs up to 3 mm long. Some of the shorter hairs may be glandular. 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: Triosteum angustifolium is similar but has bristly-hairy stems and hairless sepals with bristly margins. Triosteum perfoliatum is also similar but has styles exserted from the corolla and at least three or more pairs of leaves connate at the base.

Flowering: May to 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

Much like no. 1 [Triosteum perfoliatum L.], and not always sharply separable, but the lvs distinct, tapering to a narrow base (seldom 1-3 pairs with undilated connate base 1-2 cm wide), the hairs of the stem mostly over 0.5 mm, the sep ca 2 mm wide, the cor purplish-red, the style about equaling the cor or shortly included, and the fr bright orange-red. Rich woods and thickets; Que. and N.B. to Minn., s. to Ga., Ky., and Okla. May-July, a little after no. 1. Three vars.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.
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Morton Arboretum  
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Morton Arboretum  
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