Fouquieria (family: Fouquieriaceae) is a genus containing about 11 species of shrubs and small trees, mostly restricted to the Sonoran desert of southwestern USA and northwestern Mexico, including large part of the state of Sonora, and Baja California. This genus named in honor of P.E. Fouquier, a Parisian medical professor.

This beautiful specimen at the University of California, Riverside, Botanic Gardens is the Fouquieria splendens, commonly called the Ocotillo.

Fouquieria is the only plant that forms a spine (midrib) after the leaf abscises. Curiously, this is true of just the first set of leaves.

From a UCLA Botanic Garden newsletter:

"On the rapidly elongating young shoots, each leaf has an unusual type of petiole, in that tissues of the stem cortex become elongated and form the lower portion of the petiole. The tough, fiber-like cells of this stem cortex reinforce this tissue, so that when the leaf abscises (that is, the leaf falls away) the upper side of the petiole peels off and leaves behind a rigid, conical 'fouquieriaceous spine'.

"No other plant family makes spines in this way. The spine usually is the length of the petiole, but may extend a short distance along the midvein of the leaf blade. One might imagine that the spine evolved to protect the stems from being eaten or defoliated by browsing mammals of old, but please don't ask biologists which ones, because there is no way to know what herbivore living millions of years ago could have been responsible for shaping this adaptation!"

Over a period of several months I observed the growth of a new shoot of a Fouquieria splendens from the first leaves to their abscision, leaving the midrib of the leaf which becomes the spine:

Fouquieria columnaris, or "Boojum Tree, Cirio."



Cirio is the Spanish name - meaning candle or taper.

boojum was coined by Lewis Carroll: an imaginary animal, a particularly dangerous kind of snark; Snark, a fictional animal in Lewis Carroll's The Hunting of the Snark When explorer Godfrey Sykes encountered the plants growing on the desolate Sonoran coast in 1922, he was reminded of Carroll's story and dubbed them boojums.