Right now I put the scallions in water and cut the green part whenever I need. But I heard you can only do this for a few times before it stops growing and you have to throw it away and buy new scallions and start all over again. Is it right?
How about plant it in soil? What's the differences between planting it in soil vs. in water please? Ideally I don't want to buy scallions ever again and I want it to keep growing year after year. Since I'm in zone 10a so I think I can plant scallions all year round. Do I achieve this if I plant it in soil instead of water?
Scallions will eventually try to form a bulb. If you want green onion flavor from a plant that you can trim forever, you want chives, ideally dividing them in the spring.
I just found this article and yes, the reason you want to plant scallions in the soil is because it will grow indefinitely and you don't have to buy new scallions. If you grow it in water then you have to buy new scallions after a few cuttings.