This is an excellent tip I found on
If you are like me you end up throwing out half the green onion bunch you buy because you simply don't use them enough. Even though they are quite inexpensive to buy it still feels so wasteful. So when I came across this idea for growing your own on a window sill or outdoors I just had to try it. I happened to have some green onions in the fridge that were actually on their last legs and I was pleasantly surprised to find this actually worked perfectly and was very easy to do.
Next time you are chopping up green onions simply keep the bottom inch to 2 inches of the onion ( the part with the roots attached)
Place the cutting, root side down in a small glass or jar (a clear one is best) and fill with a bit of water, enough to cover the roots. Place the jar on your window sill.
Change the water every second day. In about 7-10 days your onions will have grown enough that you can cut off any tops you need to use in your recipes. Leave the roots in the jar and it will grow back again and again.
*if you wish you can plant a few in your garden during the warmer weather months and you should get a nice bunch of green onions growing all summer long. (I have not planted mine outside yet but plan on doing so as soon as all chance of frost is gone...better be soon! lol)
Give this great idea a try!