Four o'clock flowers are trumpet shaped, about an inch across at the end and about two inches long. They open in the evening and wilt the next morning. Four o'clocks are leafy, shrublike, multi-branched perennials which bloom throughout summer. The plants are erect and spreading, 2-3 ft tall and just as wide. They have numerous branches and opposite, pointed leaves 2-4 in long. The fragrant flowers are borne singly or in clusters, and can be red, magenta, pink, yellow or white, sometimes with more than one color on the same plant. Like Petunia, bicolored flowers can also be grown. The plants continue to produce new flowers from late spring untill fall. Four o'clocks have large, black carrot shaped tubers that can be a foot or more long. In warm regions, the roots can weigh up to 18 kg or more.