I doubt that you have killed them,remove some of the foliage and dont over water,i am sure they will power on in spring.

Nothing will kill them here, I cut them down to the ground every Autumm.

I ripped up dozen's of them not long ago and they are coming up everywhere already for the next flowering season.

I thought I cut them up small before composting, but they have started coming up in the veggie garden. I can just picture them between the tomatoes

It is still very cold (14 degrees) here and quite windy at the moment. I am worried the wind will blow the big ones over and kill them, but i am also worried about cutting them down. I was told that if you cut them back before they have died back on their own that they wont have enough food to produce flowers or new plants. Does that sound right to you guys. I have planted about 30 in a group 2m x 3m and it is in quite an exposed area. I was hoping this mass planting may protect them somewhat. I have read that some gardens have them planted this way with not much protection.

In my Bulb Express growing guide RE Canna lily

In cooler climates cut all growth back to 20cms above ground level in early Winter.

Here in south of Brissie the overnight temp has been around 5-8 degs we even have frosts, though the days are warmer so I think yours will be ok.

They dont need the old foliage as the new growth comes from the rhizomes under the ground, just put a layer of mulch on top they will be fine.

MM