My Onions Are Growing

My onions are growing, not at my backyard from my kitchen. I bought bags of onions few weeks ago and when i saw them from the kitchen tray, leaves started to grow. It has no soil or water at all. My daughter was excited as she is learning about how plants grow. But how can i explain to her that these onions grew without soil and water?

So we planted some of them in a big pot with soil, then put it by the kitchen window to get some sunlight so that she can watch them grow. I also gave some to my co-worker for his vegetable garden. Oh my, they grow fast!