Did you know that a little extra effort can make green onions last up to five weeks after purchase? Here are some step-by-step instructions for how to store green onions the best way: When it comes to making your green onions last, keeping them in a humid environment is key. But first you'll need to line up the green onions and cut the root off. Then cut them in half so that they fit inside a plastic bag. Use a paper towel to pat them down, removing any excess moisture. Then wrap the bundle in paper towels. About 3 sheets per bag is right. Place each bundle in a plastic bag, and date it. Place the bag in the crisper drawer of your fridge. When you're ready to use the onions, pat them down to remove excess moisture.