I'd say about this well:

Winter of 2009, picture taken on Jan. 26. Low for the winter was -26C (maybe a little less at my location) and the plant is located on the south wall... It is 100% burnt in the picture, and the exposed culm was killed to the ground. It had a diameter of ~1".

<img src=" " alt="winter0809xmas 026">

Same culm in February, showing the damage more obviously:

<img src=" " alt="DSC01857">

Exposure to -23C last winter partially defoliated a culm of similar diameter and did kill the top 6" or so.

This is 'regular' aureosulcata, I feel like the 'alata' form might be more cold tolerant, but I base this on nothing since my plant is still too small to even consider leaving exposed.

II agree, the hardiness ratings ive seen for P areosulcata is something like, -28C - about -32C. Im assuming this is what kills it roots and all, not just leaf damage, leaf loss, and top kill ( should be different temps if im not mistakin). I wont know 100% till I try for myself. A premature guess is that ill have very silimar resuts as you, although the question for me is, will it get top killed, or leaf burn/drop like yours?

Update on a few things too, the passiflora has been frozen, an has finally died back. IT took rain then snow and freezing temps to finish it off. Temp wise were fairly average for night temps, but daytime highes were a bit above average for november, seemed to have averaged out now. IF we get this "typical" winter we are being forcaste to have, a few nights below -25C ( mabey a weeks worth give or take), and -5c for a high. the best is, so far weve gotten somewhat deccent snowfall ( after the wet snow we had melted, then froze 👿 ), and average snow fall here is 2-5 feet, plenty of insulation..

Paul isnt it a bit late for your first har freeze? Your average first frost date is the end of september isnt it?

Jesse- The frist frost date for Toronto is in the middle of October. So the first freeze should be the end of that month. Anyway, winter is now here with a vengeance, we're getting our first real snow of the year (4 centimetres) today. And should hit below -10C this week. I've done a chart of the minimums for all of my location since 1990, so it reflects the warmer years recently, and avoids the all-time lows from 1981. If anything these ratings are a little biased toward warmer years. Toronto airport (pearson) comes out as a USDA 6a; Downtown comes out 6b; and Kingston comes out as USDA 5b (my location would almost certainly be a 5a since the airport is right on the water). I can tally up the years for Tbay if you like. This chart uses only slightly more data than the actual USDA maps.... Previously I had used 30 years of data to get USDA ratings of 5a for K-town; 5b for Pearson; and 6b (but only just) for downtown T.O...

Thats interesting paul.... To be able to grow what we want we hould all have a goo idea of our cities weather, and general climate..

The only thing that i dont like figuring out about hardiness ratings, is that the data we use isnt much at all, say 100 years to figure out a general cold weather map pf the country isnt really much information at all is it? You definelty get a good idea of what to expect, but i would think the less information you use, would give a less " proper" idea of your zone.

That being said, we know climate change is effecting us in canada, so NOT to use recent data would be folly, seeing as it could actualy raise the ratings a bit high ( i think this is the reason enviroment canada ers us to use caution when using then 2000 hardiness map). Im not making light of the hariness system, i jsut ont fully agree with the sytem in use.....

Im not sure if they are still doing it, bu enviroment canadad was aking th epublics opinion and help in updating the hardiness map. You should be able to find it on the service canada website if your interested......