Opuntia

Opuntia, also known as nopales (see below), or Paddle Cactus from the resemblance to the ball-and-paddle toy, is a genus in the cactus family, Cactaceae.

Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider a subgenus of Opuntia. Austrocylindropuntia, Corynopuntia and Micropuntia are also often included in the present genus, but like Cylindropuntia they seem rather well distinct. Brasiliopuntia and Miqueliopuntia are closer relatives of Opuntia.

The most commonly culinary species is the Indian Fig Opuntia (O. ficus-indica). Most culinary uses of the term 'prickly pear' refer to this species. Prickly pears are also known as nopal or nopales, from the Nahuatl word nōpalli for the pads, or nostle, from the Nahuatl word nōchtli for the fruit; or Paddle Cactus (from the resemblance to the ball-and-paddle toy).

Description

Prickly pear cacti typically grow with flat, rounded platyclades that are armed with two kinds of spines; large, smooth, fixed spines and small, hairlike spines called glochids that easily penetrate skin and detach from the plant. Many types of prickly pears grow into dense, tangled structures.

Prickly pear species are found in abundance in the West and Southwest of the United States and throughout much of Mexico. Prickly pears are also the only types of cactus natively found to grow far east of the Great Plains states. Prickly pear species were introduced into Australia in the late 1800s, causing major ecological damage in the eastern states (see www.northwestweeds.nsw.gov.au). They are also found in the Mediterranean region of southern Europe, especially on the island nation of Malta where they grow on cactus found all over the island. Opuntia are the most cold-tolerant of the lowland cacti, extending into western and southern Canada; one subspecies, Opuntia fragilis var. fragilis, has been found growing along the Beatton River in central British Columbia, southwest of Cecil Lake at 56° 17’ N latitude and 120° 39’ W longitude. Prickly Pears also give a fruit that is known as "Tuna" in Mexico. The fruit can be red, wine-red or yellow-orange.

Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen. This movement can be seen by gently poking the anthers of an open Opuntia flower. The same trait has evolved convergently in other cacti (e.g. Lophophora).

Chollas

Chollas, now recognized to belong into a rather distinct genus Cylindropuntia, are distinguished by having cylindrical, rather than flattened, stem segments with the large barbed spines. The stem joints of several species, notably the jumping cholla (Cylindropuntia fulgida), are very brittle on young stems, readily breaking off when the barbed spines stick to clothing or animal skin as a method of vegetative reproduction. The barbed spines can remain embedded in the skin, causing significant discomfort and sometimes injury.