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 during and after 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. However, the cochineal insect that feeds on the cactus in Mexico can be ground to produce a valuable brilliant red dye kmown as carmine or cochineal. British colonists established a cactus plantation in New South Wales in the early 1800s to supply a nascent dye industry. With hospitable conditions, sandy warm soil, there and in Queensland, these an other host cactuses spread quickly and vigorously, taking over a huge chunk of grazing and horticultural terrain, and are now prohibited throughout the island continent.