Opuntia robusta
Introduction '''''Opuntia robusta''''', the '''wheel cactus''', '''nopal tapon''', or '''camuesa''',  is a species of cactus in the family Cactaceae. It is native and endemic to central and northern Mexico to within  of the Arizona and New Mexico borders where it grow from  on rocky slopes, open shrub lands, woodlands and mixed with other cactus and succulents.
Description Plants are commonly around  high, though they may grow to over  high when supported.The flattened stem segments are fleshy, round and blue-grey in colour. These are up to  in diameter and have the length of sharp spines up to . Yellow, sessile flowers with a fleshy base are produced on the edges of the upper stem segments. These are followed by barrel-shaped fleshy fruits which are pink or purple and up to  long. ''Opuntia robusta'' has populations that are dioecious, hermaphrodite, or trioecious (containing male, female, and hermaphrodite individuals).
Taxonomy The species was first formally described in 1837 in ''Enumeratio Diagnostica Cactearum hucusque Cognitarum''. It has naturalised in the states of South Australia, New South Wales, Queensland and Victoria in Australia.
Images File:Oputniahmo.JPG|''Opuntia robusta'' flower.File:Opuntia robusta close up.jpg|''Opuntia robusta'' stem segment and immature fruit.
References