I doubt this will work. Since the plants have been outside long enough to shift to their natural bloom cycle (late spring), I doubt you could force them to bloom inside this year. I would advise you to buy fresh bulbs this fall and follow the directions given for forcing blooms for the winter. If you want to force them each winter there are directions available for that too, but you will keep the bulbs inside year around.

I think you can force them, but would not count on them for Christmas, but probably January or even February. As they winter over in the garden, I tend to leave them there and enjoy the spring bloom. If you want to force them, I would dig them now and just lay them out on their sides in a cool dark area and they will go dormant. When dormant cut off the dried foliage and keep cool until the middle of November. Pot up with one third of the bulb above the mix which should be kept moist only and in house temperatures in good light. If you are lucky they may bloom in time for the holidays. Al

So, there you go. I would take Al's word over mine any day! :)

And never cut off the thick fleshy roots!