Reproducing only by seed.
Stems at first erect but soon much-branched and spreading, 30-50cm high, rough-hairy (Figure 4).
Flowers 2-4cm in diameter with a ring of several linear bracts below the calyx (Figure 4). Calyx of 5 papery-thin united sepals, coarsely hairy on the prominent, purplish, lengthwise veins (Figure 1). Petals are yellowish with a dark or purplish-brown centre (Figure 1). Filaments united into a central column. The seedpod is globular, opening at the top, with many purplish-brown, V-shaped seeds about 2mm long (Figure 5). Flowers from July to late autumn.
Flower-of-an-hour occurs mainly in the southwestern part of southern Ontario where it can be found in row crops, open fields and waste places.
It is distinguished by its low branching habit, bluish-green leaves which are deeply 3-parted and coarsely toothed, yellow flowers with a purplish-brown eye spot, a cluster of linear bracts immediately below the calyx, and the purple-veined papery calyx enclosing the globular seedpod.
Flower-of-an-hour. A. Top of plant. B. Seedling.