USDA Zone vs Canadian Zone
Almost every gardening article online was written for the United States. The trap: an American “Zone 5” and a Canadian Zone 5 do not mean the same thing. Pick your city to see your real numbers.
Are USDA zones the same as Canadian zones?
No. The USDA system is based on winter minimum temperature alone. Natural Resources Canada’s system factors in seven variables — winter minimum, summer maximum, frost-free period, rainfall, snow cover and wind. So a Canadian “Zone 6” is defined differently from a USDA “Zone 6” even though the number looks identical. We deliberately do not convert one into the other: NRCan already publishes a separate USDA-method map of Canada for cross-border comparison.
Gardening in the US? Find your USDA zone by ZIP code at USGrowersGuide.
Unit converter
For humidity-loving plants like calatheas and ferns, a cool-mist humidifier raises the moisture in dry winter air. Check a hygrometer first: at 45% you may not need one.
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Frequently Asked Questions
What is my USDA zone in Canada?
We do not calculate one, and that is deliberate. Deriving a USDA zone would mean computing an average annual extreme minimum temperature ourselves — original research on published data, which this site does not do. Natural Resources Canada already publishes a separate USDA-method map of Canada for cross-border comparison, and that is the source to use. For anything bought in Canada, use your NRCan zone.
Will a US “Zone 5” plant survive in my Canadian Zone 5?
Not automatically. The two numbers describe different things: the American tag speaks only to winter cold, while the Canadian zone also folds in season length, snow cover and wind. And both are averages — what kills a plant is an extreme, not an average. The practical rule: when in doubt, choose the option rated one zone hardier.
Why don’t US planting dates work here?
Because they are anchored to a frost that is not yours. A US article saying “sow after your last frost, around April 15” is giving a date that is true where it was written. Keep the instruction — “after last frost” — and swap in your own date: the tool above gives it, from Environment and Climate Change Canada normals.
Sources: zones — Natural Resources Canada Plant Hardiness Zone Map (planthardiness.gc.ca); frost dates — Environment and Climate Change Canada climate normals.