The US maps and Canadian maps are a bit different but for the most part quite similar. The CDN one supposedly takes more into account than just the coldest winter temperatures.

I am including a link of the USDA hardiness map. The map extends into Southern parts of Canada. Maybe you can visually find your location on the map?

If not, you might be able to tell what your USDA zone is based on the lowest winter temperature in your location (on average). There is a chart provided. For example, if your lowest winter temperature (weÂre talking temperatures, not windchill) is normally -29 to -32 C (-25 to -20F), then the USDA chart says zone 4B.

In summary though, it's not always 100% clear. Some zone 4 stuff has been known to survive in zone 3, especially a sheltered spot.

Here is a link that might be useful: USDA zone ratings

Thanks Glen. I was just never sure on US zone hardiness compared to ours. I often admire a plant from a posting and wonder if it is hardy in my zone.

I find it easier to learn the plants natural habitat. If you know a plant likes desert conditions, and the soil in your garden is naturally moist to wet, it's probably a poor candidate.
But if I want the plant, and I think I have the right conditions for it somewhere, then I don't let a zone or two get in my way. If I'm feeling really frisky, and the plant is not terribly expensive, or I raised it from seed, I'll often push by as much as three zones.
It's surprising what survives.
Why not join a local horticultural society and ask the members. I'll bet a goodly number zone push.
And why not try to order from Canadian nurseries.

Canadian gardening sources use the U.S. Dept of Agriculture information nowadays.
There really is no reason not to go by the U.S.D.A's zones.