Opuntia
Opuntia, large genus of 150–180 species of flat-jointed cacti (family Cactaceae) native to the New World. Opuntia occurs from the Peace River in western Canada almost to the tip of South America. In the Northern Hemisphere, the brittle prickly pear (O. fragilis) is one of the most northern-ranging cacti. Several species of prickly pear, including the commonly cultivated Indian fig (O. ficus-indica) of Mexico, are grown for their edible fruits and paddles and are invasive species in South Africa, Australia, and elsewhere outside their native range.
Opuntia species are erect or spreading cacti, ranging from small low-growing shrubs to treelike specimens reaching 5 metres (16 feet) or more in height. They are composed of flat joints, with paddlelike cladodes (photosynthetic stem segments) arising one from the end of another. They readily reproduce asexually, and the paddles can be easily rooted for cultivation. In addition to longer spines, the cladodes bear characteristic glochidia—small bristles with backward-facing barbs in the areoles. (These barbs are difficult to remove from human skin.) The showy flowers are commonly yellow, pink, or orange in colour, and many feature stamens that move in response to touch, a trait that is thought to increase the pollen load of insect pollinators. The fruit is typically a reddish berry, often armed with spines.