If you like to use green onions in your cooking and as a garnish, here is an easy and inexpensive way to grow your own. I set an onion in a mug with some water in the bottom, and you can see what is growing there. When I need some, I just snip off a leaf or two and cut them up. The onion will last for quite a while and when it gets looking pathetic, I will replace it with another one.
Where I live, this time of year, the onions I have grown or purchased are sprouting enthusiastically, so that makes them grow in a mug even faster.
Here is what the roots look like:
I change the water every other day.