Night-blooming cactus

My profile states that my experience is limited to zone 6 and colder. I do not believe Cereus to be a wildflower in these zones. According to the American Horticultural Society A-Z Encyclopaedia of Garden Plants, the genus Cereus originates in South America and the West Indies. The descriptions of the species therein, however, describe them all as columnar and treelike. I can think of two explanations: they flop under culture, or the night-blooming Cereus is misnamed and really isn't a Cereus at all.