Glittertrash's Grocery store spring onions
Allium fistulosum

Last year I grew a window-box full of green onions by cutting the bottoms off some from the grocery store and potting them up, roots and all. They shot leaves up quickly, and I had months worth of fresh green onions without having to wait for them to grow from seed (tried that: bugs ate them, months of waiting over in one midnight feast).

I like this method. I harvest them leaf by leaf and don’t have to worry about the last green onions from a grocery store bunch turning to sludge in the fridge.