As described on Desert USA,

One of the strangest plants of the desert, the Night-bloomiing Cereus is a member of the Cactus Family that resembles nothing more than a dead bush most of the year. It is rarely seen in the wild because of its inconspicuousness. But for one midsummer’s night each year, its exqusitely scented flower opens as night falls, then closes forever with the first rays of the morning sun.