4. Triosteum L. (horse gentian)
Plants perennial
herbs. Stems erect or ascending, 2–8 mm in diameter, solitary or few to
several, unbranched, sometimes hollow between the nodes, moderately to densely
pubescent with shorter and/or longer, spreading hairs, some of these sometimes
gland-tipped. Leaves sessile or with indistinct, broadly winged petioles,
perfoliate or those of each pair connected by a ridge around the stem. Stipules
absent. Leaf blades simple, unlobed or the largest leaves occasionally
irregularly scalloped, with shallow, rounded lobes, or somewhat fiddle-shaped,
oblanceolate to elliptic, obovate, or oblong-obovate, the margins otherwise
entire. Flowers solitary or in dense clusters of 2–6 in the axils of the upper
leaves, clusters on each side of the stem sometimes with a leaflike bract, the
individual flowers subtended by a pair of leaflike bractlets, these longer than
the ovary. Calyx lobes 7–15 mm long, linear to narrowly triangular or narrowly
lanceolate. Corollas 9–20 mm long, zygomorphic, somewhat funnelform with a
curved tube, a slightly to strongly oblique mouth, and 5 relatively shallow
lobes, these oblong to nearly circular and sometimes somewhat overlapping, the
overall corolla yellow or red. Style 10–23 mm long. Fruits drupes, appearing
berrylike but relatively dry and mealy, 5–10 mm in diameter, more or less
spherical, orangish yellow to orangish red or red and occasionally greenish-tinged
at maturity. Nutlets usually 3, 4.5–9.5 mm long, more or less elliptic in
outline, somewhat 3-angled, with a prominent, blunt keel on the ventral side
and rounded with 4 or 5 prominent, rounded longitudinal ridges on the dorsal
side, the surface appearing somewhat encrusted or fibrous between the ribs, tan
to yellowish brown or reddish brown. Five or 6 (possibly more) species, eastern
North America, Asia.
It should be
noted that some Asian species of Triosteum have terminal inflorescences
and that various non-Missouri species differ in fruit color (Gould and
Donoghue, 2000). Ripe fruits of Triosteum spp. have been dried and
roasted for use as a coffee substitute (Ferguson, 1966a).