Fouquieria columnaris, the Boojum tree or cirio is a tree in the ocotillo family, whose other members include the ocotillos. Some taxonomists place it in the separate genus Idria. It is nearly endemic to the Baja California Peninsula, with only a small population in the Sierra Bacha of Sonora, Mexico. The plant's English name, Boojum, was given by Godfrey Sykes of the Desert Laboratory in Tucson, Arizona, and is taken from Lewis Carroll's poem "The Hunting of the Snark".

Fouquieria is a genus of 11 species of desert flowering plants, the sole genus in the family Fouquieriaceae. The genus is native to North America and includes the ocotillo and the Boojum tree or cirio. They have semisucculent stems with thinner spikes projecting from them, with leaves on the bases spikes. They are unrelated to cacti and do not look much like them; their stems are proportionately thinner than cactus stems and their leaves are larger.