Hi.
I don't know if this would be exactly like the green taro you are looking for, but last year I just bought some taro root from the Asian grocery store. It is eaten as a vegetable. It seems to be the same plant that the gardening stores sell, but it is much, much cheaper at the Asian grocery store. I grew mine in the garden, but I'm pretty sure it grows in water too.
Something else to try from the Asian grocery store is water chestnuts. They look like black-skinned, sort of flattened little balls. They turn into something that looks like a rush. They were maybe 2 feet high. They bloomed, but their bloom isn't exactly what most people would call a "flower."
