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, and can be found in enormous numbers in parts of South Africa, where it was introduced from South America. 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.

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.  [1]

There are over 200 species of prickly pear cacti. Most are found in southwestern North America, Mexico, Central America and South America. Opuntia humifusa is native to the United States east of the Rockies, where it grows in dry, sandy soils in open pine woods, prairies and scrub. Prickly pear is easy to grow, rooting readily from pads stuck in the ground, or even just lying on the surface. Grows best in full sun, in dry, sandy soil.

The sweet juicy fruits of the prickly pear, called tunas, are very popular everywhere except the United States. In fact, annual worldwide commercial production of prickly pear tunas is more than twice that of strawberries, avocados, or apricots! The pads, called nopales, are a popular vegetable in Mexico and Central America. They are usually cooked but can be eaten raw. They taste a little like green beans.

Prickly pear spines are easy enough to avoid, but watch out for the glochids, tiny hairlike bristles that occur in little tufts. They are barbed and can cause skin irritation for hours after contact.