When to whack an Elephant ?

It has been so temperate this winter in my Northern California garden that for the first year that I have had this property ( 5 yrs now ) almost all of my subtropicals did not go dormant.

Normally my cannas , alocasias and colocasias go completely dormant but this year they made it thru the winter with foliage intact.

So the big question is, when and should I whack down the Cannas and the Elephant ears to encourage new seasons growth.

Do those in warmer climates that normally have this dilemma wait until the days grow a little longer or wait until all chances of frost passes ?

When do you whack back the cannas , elephant ears and banana that held on to their foliage, albeit ratty looking foliage ?

I have had all the plants you speak of at one time or another...yes, the foliage may overwinter but look ratty like you said...I always cut back the cannas right to the ground around November...by then they are pretty much "done"...they are a rhizome, so they always come back...they are practically indestructable...
Colocasias, being a tuber, I pretty much treated the same way as Cannas...
Our winters are mild compared to yours, but they both do benefit from being cut back.
I have even mowed them down with a power mower and they return full force.
Since they are both tropicals, I don't think hacking back in fall or winter for you would hurt them...they are very forgiving...!!!!

I too have these plants, but like JapserDale, I'm in SoCal. I've relocated my cannas a couple of times, most recently at the end of November 2005, and am now seeing lots of new leafy growth. I also just removed a bunch of Elephant Ears (taro-type) yesterday, because the previous home owner didn't think about the 70-mile-hour Santa Ana winds and the lack of rainfall when planting these babies. The leaves were always getting shredded or sun burned. From the looks of the roots and buds, though, I'd say these are about a month away from new growth.

My guess is that you could probably still whack your plants, but don't wait too long as they are probably just a few weeks away from new growth in your area. Good luck!