Echinocactus grusonii, popularly known as the golden barrel cactus, golden ball or, amusingly, mother-in-law’s cushion, is a well known species of cactus, and is endemic to east-central Mexico.
It is rare and critically endangered in the wild, where it is found near Mesa de Léon in the state of Querétaro, and in the state of Hidalgo. The population was critically reduced in the 1990s, by the creation of the Zimapán Dam and reservoir in Hidalgo. The cactus grows in volcanic rock on slopes, at altitudes around 1,400 metres (4,600 ft).
Photos: Tom Zimmerman