hidden cactus corner:
Allan Gardens Conservatory, Toronto
Authors' Note: Species of plants belonging to the cactus family are native only to America. Although they are generally heat-loving, a few species of the genus Opuntia are sufficiently cold-tolerant to live in parts of Canada. One of these, the eastern prickly pear, Opuntia humifusa, thrives in the US in dry areas such as along beaches on the Atlantic coastline, and some inland areas. At the northern limit of its range, in areas along the Great Lakes in Ontario (located centrally in Canada), this species has been susceptible to territory loss by severe winter storms and is now considered locally endangered. Three other species of low-growing cacti are still flourishing in the prairie provinces of western Canada.
There's a different story in other parts of the globe, where these and related species were relocated by human activities in the sixteenth century. Owing to their edible summer fruit, prickly pears are tolerated as invasives in parts of South Africa, southern Europe, Polynesia, South America, etc. In Australia, however, they spread quickly and vigorously, taking over a huge chunk of grazing and horticultural terrain in Queensland, and are now prohibited.