Plant the tip up, plant very shallowly.
Colocasia as a general rule don't actually have a dormant period in nature. They go dormant when they get too cold. You could start them in a pot in the house now, keep damp but not wet, as soon as they sprout put them in a sunny window. Transplant them out when its consistently above 50 at night.

Ours here live year round until the first hard freeze (defined for the purposes of my colocasia as below 28 degrees for over 4-6 hours in a single night). That will usually kill them back, and they start trying to re-emerge in mid- February. If the weather cooperates, they do re-emerge and grow. If it freezes hard again, they go back in the hile til mid-March.

Thanks, that's really helpful - I appreciate it. And luckily enough, that's pretty much how I've planted them!

Hi Ornata, It is always helpful to know where they come from and how they grow there. These are native to the Himalayas and are always dormant there in the winter dry season. They then resprout when the monsoons arrive. While they can be nearly evergreen where it is warm enough I suppose this is not their normal growth habit and this is why it is a perfect species for us guys up north. Best of luck with it :o) Dan

Yep they are evergreen in warm areas, I have some that never freeze back in protected locations in my yard that went through lows of 24F. It also helps them to stay up if they are planted in bogs. Everything around them (Colocasia Black Magic, Black Marble, ALocasia macrorhizza, Xanthosoma) will go down and these little guys just keep on keeping on, like the Energizer Bunny.

Thanks for all the information. Just one worry: when they are dormant in winter (which they would be for me, as we occasionally get a frost down to 18F), don't they just rot in the combination of cold and moisture? We've had an exceptionally dry winter here and are experiencing drought conditions (yes - in London!), but that's by no means the norm. We certainly don't get the dry winters that it would experience in its native Himalayas.

We also generally have extremely dry winters, but ever since we were hit with 2 hurricanes within a week of each other in 2004 and received over 15 inches of rain, we have never dried out. We had a record rainfall in December 2005 of almost 5 inches in one night, and another record rainfall in January 2006, and over the month of February we received 12.9 inches of rain. UNHEARD OF. Our ground is saturated, the water table is only 4-6 inches below the soil, and I have had to dig a dry streambed in the back by the pool to divert water down the hill and keep it from pooling at the back door 4 inches deep. SO, I can say, NO they don't rot. At least mine don't. I also have many other "elephant ears" planted out in the natural bogs on our property (which is 5 acres)...these include Colocasias (Black Magic, Black Marble, Chicago Harlequin, Milky Way, Yellow SPlash, Imperial, fontenesii, and Fallax), ALocasias (New Guinea Gold, Macro Albo variegata, regular green, culculatta, Hilo Beauty, Portodora, Sinuata, Odora...) and Xanthosomas (regular green, Mickey Mouse, Lime Zinger, Jacquinii, etc)...all of these have been growing in water since the hurricanes in Sept 2004 and none have rotted, in fact, their stands have increased greatly.