Geohintonia

Geohintonia mexicana is one of the most fascinating and rare cacti in the world.

It was discovered only in 1992 by George Hinton (after whom it is named) in the Mexican state of Nuevo León. It was a remarkable find — an entirely new genus discovered so recently.

It is a solitary, globular cactus with a very distinctive blue-grey to grey-green colour. The body is strongly ribbed (usually 20–25 ribs) and has small woolly areoles with short spines. It looks almost like a living stone. It grows slowly and rarely exceeds about 10–12 cm in diameter. The flowers are pink to magenta and appear from the crown.

It grows exclusively on steep vertical gypsum cliffs in a very narrow canyon area in Nuevo León, Mexico — a micro-endemic habitat of only a few square kilometres. This extreme specificity makes it one of the most geographically restricted cacti in the world.

It is listed as Endangered on the IUCN Red List. The threats are serious — its habitat is tiny, it reproduces slowly, and it has been heavily targeted by illegal collectors. Trade in wild-collected specimens is prohibited under CITES Appendix I.

It is highly sought after by collectors but notoriously difficult to grow. It needs excellent drainage, mineral-rich substrate (ideally with gypsum), full sun, and very careful watering. It is often grafted to speed up growth. Seed-grown plants are available from specialist nurseries.

It belongs to tribe Cacteae in subfamily Cactoideae, and is monotypic — meaning Geohintonia mexicana is the only species in its genus.

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