Most recipes only call for the green part of the green onion. No need to toss the white bulb part of the onion…simply place the bulb root side down into a glass of water, and set in a sunny window. The green onions will regrow! You’ll never have to buy green onions again 🙂
UPDATE: My mom regrows her green onions in a little flower pot with soil. This prevents you from having to change out the water occasionally and they grow much faster and much better in the soil! Moms know best!
The Simple Elements 
What a great idea! I’ll definitely do this the next time I use green onions.