Peniocereus greggii

Peniocereus greggii, known as the Arizona queen of the night, nightblooming cereus and reina de la noche, is a cactus native to the southern United States and Mexico. It grows as a shrub with slender gray green stems about 1.2 cm wide and up to roughly 3 m long, with six to nine ribs and short white and dark spines. Its large white flowers, up to 15 to 30 cm long, smell of vanilla and open only after sundown, usually on a single night in June or July, with every plant in a given area blooming together; by nine the next morning they are gone. The fruit is oval, and the plant grows from a very large tuber that can reach 60 cm in length and 57 kg in weight. It occurs from about 300 to 1500 m in silty soils among desert scrub, and is common in the higher Sonoran Desert near Tucson. George Engelmann first described it in 1848 and the species name honors the explorer Josiah Gregg.