Cactus

The cactus is a family of succulent plants native almost entirely to the Americas, storing water in swollen stems and reduced to spines the leaves that would lose it, so as to survive in desert and drought. That endurance in the harshest country is the root of its symbolism across the New World: the cactus stands for survival, protection and the persistence of life where little else can live, its spines a natural emblem of defence and its rare, brief flowering a sign of beauty wrung from hardship.

The cactus family's desert survival rests on a specific and genuinely remarkable metabolic adaptation, Crassulacean acid metabolism or CAM photosynthesis, in which the plant opens the pores of its skin to absorb carbon dioxide only at night, when the desert air is cool and moist, and keeps them sealed through the heat of the day, drastically cutting water loss compared with an ordinary plant, real plant physiology underlying the folk reading of the cactus as a plant that seems to live on nothing. Many cactus species are also extraordinarily long-lived, the giant saguaro of the Sonoran Desert commonly reaching well over a century and sometimes two, a genuine record of endurance behind the plant's symbolism of persistence.

Sources Plants of the World OnlineRoyal Botanic Gardens, Kew with Cunningham's Encyclopedia of Magical HerbsScott Cunningham

At the centre of Mexican national and religious identity stands a cactus: the Mexica (Aztecs) were told by their god Huitzilopochtli to build their city where they found an eagle perched on a nopal, a prickly-pear cactus, growing from a rock in the lake, the sign they found at what became Tenochtitlan, and the image at the heart of the modern flag of Mexico. The prickly pear itself was sacred and sustaining, its fruit and pads a staple food, and its cochineal insects a treasured dye. In folk practice cacti are grown by doorways as guardians, their spines turning away harm. Endurance, protection and the founding of a nation gather to a spined desert plant.

Modern archaeology has confirmed the historical core of the founding story: excavations of the Templo Mayor in the heart of Mexico City, begun in the 1970s, uncovered the remains of the Aztec sacred precinct built at the very site the chroniclers describe, giving the eagle-on-the-cactus legend a genuine, excavated city beneath it rather than only a painted page. Many wild cactus species face a real and current threat from illegal poaching for the ornamental plant trade, and a large share of cactus species are now assessed as threatened or endangered, with international trade in wild specimens restricted under CITES, a modern regulatory fact that sits alongside the plant's old symbolism of endurance and survival.