Flower-of-an-hour

Hibiscus trionum, flower-of-an-hour or bladder hibiscus, is a slender, branching annual herb in the family Malvaceae, native to the Old World tropics and subtropics, probably originating in central and southern Africa and naturalised widely across southern Europe, temperate Asia, Australia and North America as a weed of disturbed and cultivated ground. Plants typically grow 20 to 50 cm tall, occasionally exceeding 80 cm, with hispid, much-branched stems and alternate, palmately three- to five-lobed leaves with deeply toothed segments. The solitary axillary flowers, each lasting only a few hours, are 3 to 5 cm wide with five pale cream to yellow petals marked by a deep maroon to purple basal blotch; an inner spectral pattern of fine striations on the petal blotch produces a structural-colour iridescence. After fertilisation the persistent, inflated, papery calyx enlarges to enclose the developing capsule, resembling a tiny five-veined lantern, a feature that gives the species several of its common names.