You don’t need to buy green onions each week…
The next time you buy green onions at the grocery store, chop up the green parts & use them as usual but save the white ends with the roots. Put the white root end into a glass with an inch or two of water, then place them on a sunny window sill. You’ll want to replace the water with fresh water every 2 days, or whenever you find it starts to look murky.
After a day or two, you’ll notice the green shoots sprouting up off the white end, and the roots in the water will get longer. In about one week, they’ll be high enough that you can trim off as much as you need, when you need it.
In this picture, we trimmed them down to the white just yesterday!