New planting zones for canada 2025

canada just updated their planting zone map and there are quite a few changes especially along the southern border.  



I remember first learning about zones and being disappointed we lived in zone 7b. Then it was 8,...and now zone 9a is expanded to include more than our tiny corrner of bc.  

With this new information, I might rethink planting my yuzu trees in the ground instead of keeping them in pots I can move inside if we get a deep frost.

I wonder what else we can grow now I had given up dreaming of having in my garden.

Interesting! Though I'm skeptical of their new zones in areas of the Prairies I know well. They haven't included winter humidity in their calculations, which is a factor in winterkill. They also don't seem to factor in the new winter surprise factor which is multiple rapid swings between almost-thaw temperatures and extreme cold temperatures -- deadly for perennials and tame trees. (None to good for roads and buildings either.)

new winter surprise factor

That sounds like our entire winter 10+C above most day, freezing most night.  I didn't know it had a name.

r ranson wrote:new winter surprise factor

That sounds like our entire winter 10+C above most day, freezing most night.  I didn't know it had a name.

Out here, it's also known as Oh FF sake, not again! Roads, driveways, and sidewalks melt just enough to form sheets of glare ice. Then we get a dump of snow on top as dance wax, and it drops to -35. Although prairie climates have always operated in long cycles, his trend is starting to look like the new normal.

I think I'm with Douglas on this one.

Yes, we appear to be having more warmer weather, particularly in some months. But this is balanced with a cold and damp "Junuary" - what the locals call the crappy weather we get in June after having glorious May weather that makes you think, "of course those tomato plants will do fine in the ground."

We also seem to be having serious cold snaps that are borderline or killers for many of those edge plants like cold hardy oranges.  Despite that, I can't resist trying them, but I need to find ways to have quick and easy protection for the 5 nights of the year that they must have that.

A friend started some avocado seeds for me. I put them in a 24" high raised bed, so the cold air would "fall away" from them. When it got cold, I put a piece of plastic over the top. Most of them looked acceptably happy. Then it snowed, and the snow stayed. Wellll... snow can be an insulator, right? But then it dropped to -5C and did so for several nights and that was that. I was too busy protecting our water system to do any more for the baby avocados and they didn't make it.

Someone I know, plants things against solid fences and puts a glass "roof" over the top. If the forecast is iffy, he can hang cloth quickly and easily down the front edge of the roof. If it's even iffier, he wraps the trees in the old fashioned incandescent Christmas tree lights and plugs them in. He might only need the lights for 5 nights a year, but it saves his edge plants. I need to up my game! (Of course, this means the trees have to be kept small through either rootstock that forces this, or significant pruning, or both, so there's no free lunch.)

Big Overalls Paul has an outdoor rocket stove hugel type thing. If it gets cold, someone can light a fire and the plants get warmed from the ground up. My climate might be too wet in the winter for that to work, but the idea is intriguing.

Freeze thaw causes plants to burn reserves, because respiration starts but photosynthesis does not.
I am chuckling at the optomistic zone for Atlantic coastal Cape Breton, where there are patches of actual tundra...

Jay Angler wrote:... A friend started some avocado seeds for me. I put them in a 24" high raised bed, so the cold air would "fall away" from them. When it got cold, I put a piece of plastic over the top. Most of them looked acceptably happy. Then it snowed, and the snow stayed. Wellll... snow can be an insulator, right? But then it dropped to -5C and did so for several nights and that was that. I was too busy protecting our water system to do any more for the baby avocados and they didn't make it.

I omitted to mention that I'd planted a few seeds in a bin on my front porch. They did nothing - not a single one germinated. So I just ignored the seeds when planting spring lettuce and a tomato plant in that bin this spring, figuring they'd compost in place.

Yesterday I went to dump the bread bowl water (our pipes don't like raw flour, my plant pots are fine with it ) on that bin and surprise surprise - I've got a baby avocado growing!  That location is *much* easier to protect than where the ones that died were. If all I do is put a jug of hot water out and throw a sheet over it, I can probably get it through the next 3 years or so. Then I will have to test it in the ground to determine if it's one of the "mountain avocados" that cope with cold snaps.

However, that does mean that I really should excavate the other area from the weeds and see if there's actually anything that may have died to the ground, but had enough root to regrow.

I think you or I are not understanding or missing something.  If I am not mistaken, the higher the minimum temperatures, the higher the zone number.  So you will not have a problem with your plants freezing more often, but with the summer heat cooking them to death.  I could be wrong or missing something, but I think something is the other way around.

Not quite.  It's more how gentle the climate is.  For our area, 9b, summer highs usually sits in the low to mid 20 C with the occasional 30C days.  Winters low sit above freezing except for a couple of weeks after new years where it could go as low as minus 10C.  

Whereas other places can easily make plus 40C in summer and minus 30C in winter.  

So the high min low in winter almost (but not everywhere) inversely correlate to the summer high when one gets this far north.

Ebo David wrote:I think you or I are not understanding or missing something.  If I am not mistaken, the higher the minimum temperatures, the higher the zone number.  So you will not have a problem with your plants freezing more often, but with the summer heat cooking them to death.  I could be wrong or missing something, but I think something is the other way around.

If I understand correctly, the Canadian zones are calculated using additional factors compared with the USA zone calculations.  More than just minimum winter temperatures are taken into account.  Canada Plant Hardiness Maps has a map linked at the bottom of the page showing how Canada's zones would look using the American minimum temperature process.