Hail to Canada's hardy cacti

by Ken Hancock

Canadians and our international friends alike seldom link the ideas of Canada and cacti growing in the wild. But from the earliest excursions of Europeans into our country, explorers have commented on our cacti. For example, Archibald Menzies (who sailed in 1791-95 with Captain George Vancouver) was the first botanist to set foot on the islands in the Straits of Georgia in May 1792. His journal records that he "was not a little surprised to meet with the Cactus opuntia (now Opuntia fragilis) thus far to the Northward. It grew plentifully, but in a very dwarf state on the Eastern point of the Island which is low, flat & dry sandy soil."

Flora Shaw, the aristocratic lady reporter of The Times of London reported in June 1898, when crossing the Prairies on the way to the Klondike gold rush, "For a thousand miles the railway track lay through wild roses of every tint from palest cream to crimson. Wild lavender accompanied them in great quantities with red columbine and spiraeas, white and pink. A handsome pale yellow cactus was also abundant and the gaillardia of the English flower gardens grew like buttercups in the grass."

However, we know that long before these records Opuntia fragilis and probably Opuntia polyacantha were used by our First Nations peoples to fix paints on the body, on wood and on buckskin. They also used the spines for fishhooks and for piercing ears.

Today we know that there are at least two genera and four species of cacti, plus a sterile hybrid, that are indigenous to Canada, with two or more occurring in five of our provinces.

Opuntia polyacantha (Many-Spined or Plains Prickly-Pear) - © Ken Hancock
Opuntia polyacantha
(Many-Spined or Plains Prickly-Pear)

It seems likely that the distribution of the various species within Canada is far wider than we currently realize. Unfortunately there are also some locations where our cacti are declining for a number of possible reasons. I hope that this article encourages you to look for our native cacti while, at the same time, conserving them. They can be simply grown in this area in any well-drained rock garden.

The two cacti genera indigenous to Canada are Escobaria (Pin Cushion cactus) and Opuntia (Prickly-Pear cactus). Only one Escobaria species is confirmed, namely Escobaria vivipara (Prairie Pin Cushion).

On the other hand, four species of Opuntia have been located: Opuntia fragilis (Brittle Prickly-Pear), Opuntia humifusa (Eastern Prickly-Pear), Opuntia polyacantha (Many-Spined or Plains Prickly-Pear) and Opuntia x columbiana (proposed species, Bruce Parfitt).

Geographically our cacti extend from the most southernly mainland point of Canada, Pelee National Park in Ontario (only Canadian location of Opuntia humifusa) to the Peace River region of Northern B.C. and Northern Alberta, where Opuntia fragilis have been found.

Travelling west to east, cacti extend from Denman Island, B.C. where Opuntia fragilis are located, to Kaladar, Ontario, the most easterly confirmed location of any cacti (also Opuntia fragilis) and now under protection. Until 1999, that distinction was held by an Opuntia fragilis population in the pine woods off Knoxdale Road in Nepean, which has died off likely from natural causes.

There appears to be no climatic or geographic reason why Opuntia fragilis has not extended its range to favourable locations in Southern Québec. So far there are no confirmed findings, but the writer will be checking one report in the spring.

The acceptance and profusion of our cacti varies greatly across the country. Up to recently Opuntia fragilis and Opuntia polyacantha were legally noxious weeds in Alberta and Saskatchewan, while both, together with Escobaria vivipara, were classified as such in Manitoba. This classification (now rescinded in all three provinces) required eradication of the plants wherever found.

By contrast Opuntia humifusa, which is currently only found in its native state at three sites in south-western Ontario, was assigned the official status of Endangered in Canada in 1985. In the southern areas of Alberta and Saskatchewan both Opuntia fragilis and Opuntia polyacantha are so numerous there have been moves in the past to consider biological and other control methods.

A book by two U.S. biologists (Maw and Molloy) notes that cacti provide food for many birds and mammals, including rabbits, gophers, squirrels and deer. They conclude that the value of cactus in the ecosystem has not always been appreciated. During drought or under heavy grazing, cactus reduces soil erosion. Clumps of cactus conserve moisture by holding snow, and after summer showers, the soil within the clumps remains moist for several hours longer than soil surrounding them."

I and many of my cactus-loving friends grow all of these hardy Canadian plants in our gardens, together with many other hardy cacti, throughout the year on well drained, gravelly soil, in a southern exposure. The reward is bountiful flowers every year.



Previously published in Ottawa Valley Rock Garden & Horticultural Society Newsletter, Volume 11, Number 5, January 2003. Reproduced here with permission. www.ovrghs.ca


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