Hibiscus trionum L.

Hibiscus trionum plant

Family - Malvaceae

Stems - Herbaceous, erect, branching, to -1m tall, terete, sub-hollow, stellate and forked pubescent, also with thin vertical lines of lanose hairs in the internodes (mostly in the upper stems), scabrous due to the swollen bases of the stellate and forked hairs. Hairs branching and clear.

Hibiscus trionum stemStem.

Leaves - Alternate, petiolate, stipulate, deeply divided or trifoliolate. Stipules attenuate, 3-7mm long, 1mm broad at the base, with coarse long cilia on margins. Petioles to +3cm long, pubescent as the stem, with a very shallow adaxial groove (the groove pubescent). Leaf blades divided all the way (or nearly so) to the base. Leaf divisions pinnately lobed, to +5cm long, 2.5-3cm broad. The lobes rounded at the apex. Blades glabrous adaxially, stellate pubescent abaxially.

Hibiscus trionum leaves

Inflorescence - Single axillary flowers along the length of the stems and branches. Peduncles to +/-2.5cm long in flower, slightly longer in fruit, dense stellate pubescent and lanate (in lines). Peduncle with an obvious joint in the apical 1/3. Pubescence after joint becoming long-ciliate and branching as well as stellate. Involucre subtending the calyx of 10 linear-attenuate bracts. Bracts 7-8mm long in flower, to 1cm in fruit, long-ciliate, green.

Flowers - Corolla deeply 5-lobed, pubescent externally, mostly glabrous internally, +/-4cm broad, pale yellow with a wine-colored center. Corolla lobes joined at the base and forming the stamen column. Stamen column to 1.1cm long, wine-colored, glandular. The glands wine-colored. Stamens many. Free portion of filaments to +/-3mm long, sparse glandular. Anthers yellow-orange, 1mm long and broad. Style exserted just beyond the stamen column, glabrous, whitish-translucent, 5-lobed at the apex. Stigmas 5, wine-colored, globose-capitate, +/-1mm in diameter. Ovary green, ovoid, densely antrorse appressed pubescent, 4mm long in flower, 3mm in diameter, 5-locular, many-ovuled. Placentation axile. Calyx 5-lobed. The tube to 3-4mm long in flower. Lobes ovate-triangular, entire, acute, to 1cm long in flower, 7-8mm broad, each with 3 evident veins(nerves) externally (the entire calyx is 20-nerved). Nerves appearing purplish-dotted because of the purple swollen bases of the hairs on them. The hairs forked, long ciliate, clear. Tissue between the nerves translucent-green. Calyx lobes antrorse pubescent internally near the apex, glabrous in the medial portion, and with thickened whitish hairs at the base near the corolla tube. Also with stellate pubescence at the base amongst the thickened white hairs. Calyx inflated in fruit and drying to a brown color. Capsule 5-valved, longitudinally dehiscing, 1.4cm long, brownish-black, ciliate. Seeds dark brown, sparsely tuberculate, 2-2.5mm long, reniform.

Hibiscus trionum calyxCalyx.

Hibiscus trionum flower

Hibiscus trionum fruitFruit.

Flowering - June - September.

Habitat - Waste ground, fields, roadsides, railroads.

Origin - Native to Europe.

Other info. - This striking species can be found throughout Missouri. The plant is commonly called "Flower of an Hour" because the flowers only open fully for an hour or two per day. The plant does well in cultivation and grows from seed. Since it is an introduced species, it should not be willingly spread in the wild.

Photographs taken in Brown Summit, NC., 9-14-02.


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