Elephant ears (Colocasia) will usually show damage from even a light frost, and a hard frost will destroy the leaves BUT it won't kill the plant. I usually wait until a hard frost kills the foliage, then dig them up, cut off the leaves at the base, and let them dry out in a cool dry place. The bases of the leaves can be pulled off the tuber after they have finished drying out. I store the tubers cool and dry in my attic, and have had no problems (but then again my winter is a lot shorter than yours!).

This applies to the standard big green elephant ears (Colocasia esculenta). I can't comment on 'Portadora' which is an Alocasia--I haven't grown it.

Colocasia 'Black Magic' is a special case, in part because there are 2 completely different plants going around under this name. One is a clumper, and I can't really comment on overwintering it as I haven't grown it. The other is a runner and produces numerous long rhizomes, and has been re-named as 'Black Runner' but I've gotten it under the name 'Black Magic'. This one produces a very small tuber (even on giant plants) and I have never been able to overwinter it as a dormant tuber; it always rots. I have only been able to overwinter it by propagating it from the small plantlets that form at the ends of the runners and keeping them growing indoors over the winter.

I am in zone 5b, and here is my experience:

Bird of paradise (BOP)- can not take frost - keep as a house plant
Giant BOP - same as above.

EE blackmagic - after frost kills leaves, lift and dry tubers, wrap in saran wrap, and keep in a cool, not cold, and dark place. Check every month to make sure it isn't rotting. You can also grow this as a house plant.
aztec lily - sprekelia - I have no experience with this but would think the saran wrap technique would work here, too. I would think it would be like other lilys - allow pot to dry out completely, DO NOT WATER, store in a cool, dark place until spring, then start watering lightly until it begins to grow again.
EE portodora - haven't grown this one.

pregnant onion - this makes a lovely house plant, blooming fragrant white blooms on long stems about mid-winter, if it gets sun. I have always grown this one as an attractive house plant.

Bird Of Paradise NEEDS to come in. If it gets hit by a light frost, it will be a slow recovery - a hard frost will most likely kill it.

Thx so much JohnnieB, reinbeaux and kayjones.

My garden had a mass exodus last night. I'm now landscaping in the livingroom! Trying to figure out how to arrange the plants so hubby and kids can still see the TV!

Oh I forgot about this one--I kept it as a houseplant last winter but do I have to? - EE macrorrhiza. Gees, it was just a tiny trade last fall- It must weigh #40 now!! The leaves are only 12" long tho- is that max size they will get?

Well I put it in the garage for now 'til yah LMK.

Thx again

Karen