This is a nifty trick I picked up from my sister-in-law. I almost never buy scallions because 3/4ths of the bunch always ends up rotting in the vegetable bin, but it turns out you can keep scallions alive in water near a window. The more light they get the darker green they'll be, but they aren't that picky. You can even use all of the green part and drop the white root end in the water and it'll grow again. You can pull out that slimy bunch from the fridge, discard all the funk and as long as the root tip is okay, it'll grow back... just make sure the water level is below the greens so they don't rot again. I bought these babies almost 2 months ago and I've harvested them at least 5 times now.