Plants are described as being hardy when they can withstand winter conditions without added protection. When it comes to selecting the best plants for your garden, it’s important to know what hardiness zone you live in.
What is a hardiness zone?
Hardiness zones are given geographical areas defined by different climatic variables. Natural Resources Canada has put together a map of Canada’s hardiness zones, which includes various factors such as temperature, rainfall and snowfall, the number of days above freezing, and wind speed. The map was updated in 2025 and reflects the ongoing effects of climate change.
The Canada Plant Hardiness Zone Map is made up of 10 zones, numbered from 0 to 9. The higher the zone number, the warmer the weather and the longer the growing season.
Each zone is divided into sub-zones a and b, with b being slightly warmer than a. For example, the Island of Montreal is in zone 5b (6a for some areas), whereas the city of Amos is in zone 2a.
To grow plants in a given zone, they must have a hardiness rating that is equal or inferior to that zone. In zone 4, for example, you can grow plants rated for zones 1 to 4. Growing plants rated for hardiness zones 5 or 6 is risky unless they’re planted in a microclimate or are given additional winter protection. Plants with even higher hardiness zone ratings should either be treated like annuals or brought inside for the winter.
What is your municipality’s hardiness zone?
Natural Resources Canada’s website has an interactive map that shows hardiness zones across the country. You can also look up hardiness zones by municipality in each province and territory. The most recently updated hardiness zone is represented in the second column that comes up in the search results.
The effect of microclimates on plant hardiness
On top of your municipality’s hardiness zone, there may be localized climatic conditions in your yard that should be taken into consideration. Several factors can create a warmer or colder microclimate in your garden, such as:
- your yard’s orientation and topography
- your yard’s exposure to prevailing winds
- snow accumulation in your yard (snow is a great insulator!)
- hedges, fences, buildings, etc. that provide shelter from the elements or a nearby body of water
- your garden’s proximity to paved surfaces (concrete, asphalt, etc.) or walls
It’s important to carefully observe your yard so you can select plants that have the best chances of thriving.
What is a plant’s hardiness rating?
Only herbaceous and woody perennial (trees, shrubs, and vines) and biennials have hardiness ratings since true annuals only live for a year or less.
Plant hardiness ratings can be found in books, on gardening websites, and often on plant labels in garden centres. If there is nothing on the label, the plant is most likely an annual or a non-hardy perennial, which is typically treated like an annual.
It’s important not to confuse Canadian and U.S. hardiness zones
Canada’s hardiness zone system is different from the one used in the United States. The hardiness zone map created by the United States’ Department of Agriculture (USDA) is only based on average annual minimum temperature. This results in a difference of roughly one full zone between the two systems, with zone 4b in the U.S. corresponding to zone 5b in Canada.
While other countries have developed different systems, the USDA’s system is the most commonly used, so it’s important to keep that in mind when consulting written work and websites from the U.S., Europe, and other countries around the world.