Indoor Gardening . . . In The Garage?

This is my Aunt and those are her green onions!  A few weeks ago, she and my Uncle emailed about rescuing these onions from their community garden plot.
Here's what they said:

Dear Kate,

When that first real cold snap came and we were afraid for the green onions in the garden we dug them up along with a lot of their dirt and put them in this tupper ware. We hoped to be able to use them up before they croaked/rotted/whatever, but we found that they continued to grow in the garage. We add a little water periodically, and we're using them up as we need them...Amazing!!...xoxox W

And here is the picture!