Tropicals & Tender Perennials: What's the frost hardiest Canna?, 1 by dyzzypyxxy

dyzzypyxxy wrote:
The variety sounds like Red Futurity, or one of those types. You're sure they don't just re-plant them each spring?

I'm of the same opinion as Dale, the issue with cannas being that they have those big fat fleshy rhizomes full of water that must not freeze during winter. They go mushy and rot.

A warm micro-climate may be allowing the cannas to survive through your bitter winters with a deep mulch. Take a look at the exposure. I'll bet the bed they're in is on the south side of a building, and maybe it's close in with windows nearby that let some heat out, or a brick or stone wall that acts as a heat sink to collect solar heat and release it during the nights. If the building has a heated basement adjacent to the canna bed, that really could be keeping the bed warm. If you ever walk by that flower bed in the winter, take note if the snow melts off it quickly etc.

I had just such a situation in a south-facing bed at my house in Salt Lake City. Some very tender plants lived through winters there, at 4500ft. of altitude, and long, cold snowy winters. In fact it was so warm the snow used to melt and I'd have to water a little bit to keep the perennials in that bed from dying from dessication.

In any case, I'd try buying some next year and plant them in your most protected, sunny south-facing spot. Then when the time comes, just lift a couple of rhizomes as insurance. Leave the rest in place, mulch like crazy and see if they come back.