Bury it in the ground, in the pot.

Donn has offered about the best advice regarding your situation. I learned this as I tried both avenues of over wintering grasses.

If you were to over winter in an unheated garage you will need to water the plant periodically. Without going into a long diatribe a plant being outside will get moisture from winter snows and or rains.

If anyone lives in an area that gets winter temps below freezing they need to water their plants in the winter when there is a winter thaw cycle.

Not many realize this and make the statement in the spring they lost plants due to the hard winter freeze. DUH !!! In most cases it called lack of moisture.

I must admit it does look rather goofy to see someone watering their lawn, tees, shrubs and grasses in the middle of winter but plants don't really "die", they go dormant.

That's what happens to ornamental grasses that are "cool" season and "warm" season grasses. Cool season grasses will turn shades of green brown in the heat of summer but green up in the fall when temps get cooler.

Jake

Perhaps this will not be well received but another option is to simply compost the removed chunk and try the whole deal again in late spring. Why sweat it really if the parent clump is that massive -- unless of course it was a royal pain in the ass to get that division...which it undoubtedly was. Sounds like the parent clump is due for some more division/reduction in size anyway this coming spring. Is there any dieout or decline in vigor in the center yet?