Your question is a little too general.
"Elephant Ears" is a generic term that is, unfortunately very broad and doesn't really lend itself to a brief explanation of your question.

The Black Magic and Illustris that you bought are Colocasias, and you are correct, they don't really form big "bulbs" that you can lift and store for the winter. In fact, I really can't think of a single colocasia that does do that. Fontanessii forms somewhat of a bulb, but not one I would ever try to dig. Usually, colocasia need to either be kept up and going all season, or allowed to go dormant still in the soil and stored in the containers in a cool dry place that won't freeze. Here in North Florida, Colocasias generally start to go dormant about November when the rain really dries up, and they disappear with the first frost altogether. They re-emerge like gangbusters in Spring when water and warmth return. But bear in mind we get no snow, no ice and our ground doesn;t freeze.

The best "elephant ears" for the kind of overwintering you are talking about are probably Alocasias, but even within that group, there are many different species and hybrids and not all are equally cold hardy. The plain old green Alocasia macrorhizza (also called Upright Elephant Ear) is one that makes a really good bulb that can be dug. But some of the other forms of macrorhizza (like the Black Stem, and the albo-variegata) don't do the same thing to the same extent. But Alocasia Odora is completely different, its a trunk former over time and not a bulb former, as is Alocasia culcullata. You can use the ones that they sell in the grocery stores all over now, the shiny ones that are forms of xAmazonica, but these are truly NOT cold hardy in the least and have to be maintained as houseplants in cold weather.

The Xanthosomas are pretty cold hardy (to about zone 7 I think) and they do form tubers that can generally be dug up and stored.

If you like the look of "elephant ears" and don't even want to go to the hassle of overwintering at all, you can replace them every year very very cheaply by going to either your grocery store, the Asian or Indian food market and many health food stores and buying tubers dirt cheap from the produce section. These may be labeled Taro, Eddo, or Malanga. They are none other than...elephant ears!

Thank you so much for your reply. I guess I shouldnÂt have used the name Elephant EarÂs since like you said it was too general. But since I didnÂt care if what was suggested was Alocasias, Colocasias, or Xanthosomas it was the best name I could think of. I guess the best thing I can do is just to add a couple every year and see which ones do the best.

Thanks again,
Jane

Jane,

I'm sure I have a couple of the same EE's (Walmart buy) you have (huge bulbs) - I can't imagine they have any variance. Anyway, I'm also in Z5 and managed to help mine survive a winter in the ground last year. They are right next to my white house and have full south exposure. I mulched them heavily with straw after the first hard freeze and surprisingly enough they came back and flourished this summer.

I would not, however, try that with your Black Magic and Illustris - those definitely need to come indoors.

Cheryl