Hibiscus trionum - Flower of an Hour

Flower of an Hour is an annual herb, erect, branching, up to 1 m tall. Stem is round, sub-hollow, velvety, also with thin vertical lines of hairs in the internodes (mostly in the upper stems), scabrous due to the swollen bases of hairs. Leaves are alternate, stalked, stipulate, deeply divided or trifoliolate. Leaf-stalks are up to 3 cm long, velvety as the stem, with a very shallow adaxial groove. Leaf blades are divided all the way (or nearly so) to the base. Leaf divisions are pinnately lobed, up to 5cm long, 2.5-3cm broad. The lobes are rounded at the tip. Blades are hairless above, velvety below. From the axils of the leaves, there develops single flowers from hairy stalks. Each flower is about 2 inches across, consisting of 5 rounded petals that are white or pale yellow, a large calyx that is divided into 5 segments, a pistil with a divided style, and numerous stamens with golden yellow anthers. Each petal is purple at the base. The purple style is divided into 5 short filaments with knobby tips. The segments of the calyx are white and membranous. Each calyx segment has several longitudinal nerves that are purple or green and hairy. At the base of each calyx, there are several spreading bracts that are long and narrow.