Pretty-by-night and four-o-clock flower are both common names for the flowering herb Mirabilis jalapa, cultivated as an ornamental plant. Both refer to how its flowers open in the evening or at night.
M. jalapa is native to Peru, and is also known more rarely as the "marvel of Peru". It needs a climate that is dry and frost-free, with well-drained soil, to grow well. While it is a perennial, in some colder climates it can be grown as an annual, since it will flower in its first year.