, the four-o-clock family, are a group of shrubs, small trees, vines and herbs that produce clusters of flowers from the leaf axils; either spherical, flat-topped or elongated. Leaves are undivided, and oppositely arranged along the stems. Flowers are usually radially symmetric; they lack petals but instead have four or five petal-like sepals, often fused into a trumpet-shaped corolla. There may be just one stamen or up to several dozen. The flower clusters are often subtended by a whorl of bracts. Plants generally inhabit tropical or subtropical regions. The common name refers to the late blooming time of many of the species; flowers tend to open late afternoon, closing during the following morning. The US has just over 100 species, in 15 genera.