Opuntia Named for the Greek word "opsis," meaning "appearance," and referring to its resemblance to a specific flowering plant, larkspur (Delphinium), opuntia is a genus of more than 100 species of cacti. The pale green stem segments on some species fold up at night or in cloudy weather, unlike most other cacti, which usually fold up only during the heat of the day. There are many hybrids and cultivars, and some species have yellow, pink, red, or purple flowers. The size and shape of the fruit vary widely among opuntia species: Some look like lollipops; others resemble cornichons or gherkins.
The name prickly pear refers to any one of a number of cactus species including opuntia that have glochids, small bristles with one or more fine spines on the tip, such as the claret cup and Indian fig opuntias.
Native to North America and Asia, prickly pear species are cultivated around the world in warm regions where they make attractive house plants. Historically used by natives of the southwest United States and Mexico, prickly pear cactus fruit is edible, although most species are not sweet enough to be considered palatable.
The term "prickly pear" refers to a large number of opuntia species or hybrids/cultivars that have flat joints along a thick green stem called a cladode, with small spines on the end. The stem joints are known as cladodes, singular: cladode. Prickly pear species grow into different shapes and sizes, but most are columnar, rounded cacti that can reach over 5 meters tall. Unlike some other types of cacti, prickly pears never have spineless varieties but are covered with clusters of spines. Although they are called "prickly pears", almost all species have leaves that can be pulled off to reveal glochid-barbed spines in their place. The stems grow one on top of the other when new growth is formed in the axils of the previous stem. All species of opuntia have flat oval seeds that require extensive dispersal distances to ensure genetic drift from others of its kind.
The glochids often fall off the plant as it moves from location to location, and are a form of very effective adaptation to seed distribution by both attaching themselves to animals and being easily spread in their manure
Opuntia produce flowers that are usually yellow or orange and sometimes brownish or reddish. Because Opuntia leaves are partly photosynthetic, flower colors range from green to white depending on climate and soil conditions. Opuntia flowers may be single or appear in clusters.