We are currently experiencing a particularly cold winter in Eastern North America. While the thermometer indicates –24 °C, I thought it would be rather nice to write a column on cacti. So, I decided to present you a few perennial cactuses that could be planted in your garden next summer. Indestructible cactus, perfectly well adapted to cold climates! On the introduction picture you can see an Opuntia fragilis ‘Feldberg’ flower (photo : Dornenwolf).

Of the four species of cactus native to Canada, the brittle prickly pear (Opuntia fragilis) is undoubtedly the most robust of all. It can grow up to 58º N latitude in Alberta, less than 8° from the Arctic Circle! Several colonies can also be observed in other Prairie provinces and in Eastern Ontario. This is a rather atypical opuntia, since its spherical stems are not flattened like most other species. Its stems form a low and dense mat that nearly covers itself with pretty yellow flowers during a few weeks in early summer.

Spinystar (<em>Escobaria vivipara</em>) (photo : Stan Shebs).

Hang on to your hat, the rest of this story is mind-blowing! Scientists have determined that brittle prickly pear withstands temperatures around –50 °C in its natural habitat. In addition, they submitted O. fragilis to a temperature of –70 °C and immersed it in liquid nitrogen at –196 °C after a slow freezing to –40 °C. 50% of the brittle prickly pear stems have survived to this extreme treatment! Unbelievable, but true! For its part, Opuntia polyacantha can resist to about –40 ° C, while the Eastern prickly pear (O. humifusa) and the spinystar (Escobaria vivipara), two other Canadian native cacti, tolerate temperatures around –35 ° C.

Will cactus be Canada’s floral emblem next summer?

Plains prickly pear (<em>Opuntia polyacantha</em>) (photo : Matt Lavin).