Plant Hardiness Zones

How can you tell if a perennial plant will survive a Manitoba winter? You can get an idea from the hardiness zone. Hardiness zones divide Canada, the US and Mexico into 11 zones based on roughly 10 degree Fahrenheit differences in average annual minimum temperature. Plant tags will indicate a range of zones where the plant will be able to survive a typical winter. The lower the zone number, the colder the winter. Zones 0-8 are each divided into sub-zones indicated by an “a” or “b” (where “b” is milder than “a”). Natural Resources Canada publishes maps of Canadian hardiness zones, which are based on a number of factors other than just minimum temperature. However, since most plant tags reference the USDA hardiness zone, that’s probably the best one to use.

Manitoba ranges from Zone 2a in the North to Zone 4a in the Southern parts of the Red River Valley. Winnipeg and the South Interlake area are considered Zone 3b. That said, there are many other factors that can impact a plant’s prospects of winter survival in your yard. Local elevation, the position of buildings, wind patterns, variations in snowfall… all of these can create micro-climates that can make a huge difference to which plants can live in your yard. In these micro-climates, with some extra protection like mulching in the fall and piling on some extra snow in the winter, plants rated Zone 4 or maybe even 5 might be able to survive a Manitoba winter. Conversely, some colder micro-climates might be unsuitable for even Zone 3 plants.

In the Winnipeg and South Interlake area, you can feel confident that healthy, well-established plants rated Zone 3b and lower will be good selections for the casual gardener, and Zone 4a for those who are willing to experiment to expand their options.