Triosteum perfoliatum L.

Triosteum perfoliatum plant

Family - Caprifoliaceae

Stems - Single or multiple from the base, erect, herbaceous, fistulose, to 1m tall, simple, with short glandular pubescence and longer non-glandular hairs.

Triosteum perfoliatum stem

Leaves - Opposite, sessile to perfoliate (the lower and middle leaves perfoliate). Blades widest near the apex, acuminate, entire, dull green above, lighter green abaxially, densely short-pubescent abaxially, less pubescent adaxially, to +20cm long, +8cm broad. Veins expressed abaxially.

Triosteum perfoliatum leaves

Inflorescence - 1-6 sessile flowers in the leaf axils.

Flowers - Corolla yellowish to reddish-purple, tubular, glandular pubescent externally, mostly glabrous internally, -2cm long, 5-lobed, gibbous at the base with a small reservoir for collecting nectar. Lobes rounded at the apex, 5-6mm long, 5mm broad. Stamens 5, alternating with the corolla lobes, attached along the entire length on the corolla tube, included. Filaments free for half their length (+/-5mm), pubescent, yellow. Anthers yellow, 4-5mm long. Style exserted, to 2cm long, pubescent, whitish to pale yellow. Stigma capitate, 4-lobed, 2-3mm broad. Ovary inferior, 3-4-locular, 3-4-seeded(?). Calyx lobes 5, spreading, linear, glandular and simple pubescent, typically reddish, accrescent, +/-1.5cm long, +/-2mm broad in flower. Calyx tube green, subglobose, densely glandular and simple pubescent, 3mm in diameter in flower, accrescent.

Triosteum perfoliatum flowers

Triosteum perfoliatum calyxCalyx lobes.

Flowering - May - July.

Habitat - Dry open woods and thickets.

Origin - Native to U.S.

Other info. - This attractive species can be found throughout Missouri except in the extreme southeastern corner of the state. The plant is quite stout and would make an interesting garden specimen. Many flying insects are attracted to the tubular flowers.

Photographs taken in Eminence, MO., 5-23-03.