Thanks for the good info. Would you advise me to start them under lights and keep them growing all winter? It will be inconvenient in my small house, as there are 8 (!) large tubers! But this was a real windfall for me, and I want to give them the best care I can. Would you mind advising a planting mix and pot size? I don't usually grow in pots.

It'll be a matter for you to decide if you want to share your limited house space with these plants, all of my Colocasia are strictly outside. You'll want a very organic type of soil mix and one that drains well. With the size these grow to it would be better to start with a larger pot, just don't over water as they don't need it during the winter. Keep them in the brightest light you can provide.

In the central eastern US my experience with potted Colocasias indoors for the winter is that 1/3 to 1/2 of them die (from mold/fungus...I watered too much) and 100% of them slowly get smaller and thinner with less leaves leading up to spring. Other people have better luck than me. But if they make it to spring and you plant them outdoors they can do great. And possibly much better than ones not overwintered indoors.

For example, In spring 2017 I had a small edible Colocasia corm, planted it outdoors and it grew into a 10" plant with 4 leaves by fall. Then I potted it and brought it indoors for the winter. By spring 2018 it was only 6" with barely 2 thin leaves that were turning yellow. I then planted it in the ground outdoors. Right now it is a clump of 5 larger plants with 5 smaller plants. It is 3'-9" tall by 5ft wide and looks great. I just now measured it. I had a similar experience the previous year with a different Colocasia. It became my tallest EE of 2017.

So maybe try 1 or 2 as indoor plants with low or no expectations. Keep the rest in bags of peat moss in a cool dry but not too dry place over the winter. Just something to think about.

Thanks to Jay and TropicBreeze for your advice. I've had good luck growing colocasias to very large plants outdoors here in Oregon, but have never been in a situation like this with special bulbs late in the season. For now, I put the Jack's Giants in pots outdoors with rich, moist soil and rooting hormone, in bright sun. I won't water them again unless they put out leaves. Then I'll have to make a decision about how many to bring inside. Hope they all live and thrive. Thanks again for your input.

I know I'm late to the party, but just curious if you got them to break dormancy so late in the season? I know a lot of my colocasias won't wake up until the ground temps get high enough.