Artichoke cactus  (Obregonia denegrii)

Classified as Vulnerable (VU - B1ab(v)+2ab(v)) on the IUCN Red List 2002 (1), and listed on Appendix I of CITES (3).

This small cactus is just visible above the surface of the ground, as the heads emerge only slightly from the larger underground root system (2). The distinctive appearance of the head, which has given rise to the common name of 'artichoke cactus', is formed by the spirally arranged, erect tubercles; at the tip of each, there are 3 - 4 flexible spines (2). White flowers emerge from the centre of the whorl of tubercles, and these develop into whitish-brown fruits if cross-pollination is successful (2).

Found only within the Valley of Jaumave in the state of Tamaulipas in eastern Mexico (2).

The artichoke cactus is found in semi-desert and shrubland at elevations of around 600 - 700 metres above sea level (4). It is often found on rocky, gentle slopes in limestone gravel (2).

This striking cactus produces flowers during the summer months. Fruits develop if the flowers are successfully fertilised through cross-pollination; the fruits dry and then split open, allowing the seeds to be washed away (and therefore dispersed) by rain (2).

Artichoke cacti are in high demand for commercial trade and have previously been collected in large numbers (2). Local people use this species to treat rheumatism, and over-collection for this reason is also a threat (1). Habitat destruction, through urban development, road construction and livestock grazing pose further threats to survival; accelerated erosion has been observed at both known sites of this species (2). The total population is thought to have decreased by as much as 50% over the past 50 years; although around 5,000 individuals still remain (1).

International trade in wild-taken plants and seeds of the artichoke cactus is banned by its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3). The species is also protected under Mexican law (5), although illegal collection does still occur (1). It has been suggested that the Valley of Jaumave is a prime candidate for a nature reserve (2), which if created would preserve the future of this appealing cactus amongst various others.