Many of us might think of cacti as indoor plants, typically displayed on a windowsill or in a greenhouse. While many species thrive in subtropical and tropical climates, there are also several hardy species plus their various cultivars and hybrids, that are well-suited for cold, freezing winters. Some, like Opuntia fragilis (the brittle prickly pear), can even withstand the harshest conditions, growing naturally from British Columbia to northwestern Ontario, and tolerating temperatures as low as Zone 2!