When you buy scallions at the grocery store, they come in a bundle with the roots still intact at the bottom of the vegetable. These roots are the key to scallions regrowing, over and over again. And all you need is a small clear glass, water, and sunlight. You’ll have sustainable reusable scallions FOREVER.
When using the scallion for cooking, cut at the white part, (to use the green part for food) making sure you leave about 1-2 inches left of the scallion.
Place the white part, roots facing down in a small glass of water. If you have just one it might float around, but once you have a few in there you can rubber band them together to make them stay root down, or crowd them in so they do).
Place the cup on your window sill making sure it gets plenty of sunlight, and then watch your scallions grow! Make sure to swap out the water for clean water every few days. You can recut, and regrow them multiple times!