Yum, I love green onions. I vaguely remember reading a year or so ago that scallions could be regrown by planting their root stumps after you've chopped them up and eaten the tops. After trying it a few times myself, I'd like to proclaim to the internet world that, yes, it IS possible!
I've actually been getting a kick out of growing scallions indoors. I started bunching onions (aka green onions) by seed in my garden last summer and it took an entire season before they had matured. By purchasing scallions from the store, eating them like I usually would, then growing them from the roots, I basically get two scallions for the price of one. Plus, it only takes two to three weeks for the new plants to reach full length. In addition to sprouts, I can now grow two different veggies at home in the dead of winter.
Regrowing scallions from their root stumps is easy. First, save up a bunch of roots so you plant them all at once. It is possible to save over a month's worth of roots in a dry, sealed plastic bag in the fridge and grow them at a later point. Next, find a potting container that holds about three inches of soil. The deep pot that I used in the above photo is a bit of an over kill as the new scallion roots only grow a few inches deep. Plant the stumps, root down, and cover with a little soil. Water and tend to the scallions like you would a houseplant, although direct sunlight isn't necessary. When the scallions reach a height at which you'd like to eat them, you can snip the tops off, leaving the roots in place, and grow another round. The second round of scallions, however, are rather wimpy and not really worth it. If you don't have soil or a potting container, I've since read that scallion roots can be grown in a glass with a small amount of water. I've yet to try this method though. Scallion roots can also be grown outdoors during the warmer months. I planted a few roots in my Movable Garden last Fall and they grew well.
I think this would be a great project for kids, but its also fun for adults have a some green edibles growing in your kitchen. On a side note, I've also since read that leeks and celery can also be regrown from their roots. I really want to try this! In Montana, growing leeks from seed can take six months, but I imagine that growing them from roots is a lot quicker.
Have you tried growing scallions at home? Do you know of any other vegetables that can easily be grown in your kitchen?