How To Regrow Onions. Enjoy them throughout the growing season in stir fries, salads or diced to make savory pancakes. Leave on for at least 15 minutes (longer if you can tolerate the smell) and then wash out using a mild shampoo.

Place the tops in a container of water and new, green tops should begin to grow in a matter of days. To extract the juice, you can use a food processor, a blender, a grater or a juicer. Before you throw out the green onion roots, consider using them to regrow green onions.