I like the concept of growing something and feeding it to your creatures, making them stronger. But I think that Rice Plant might be the wrong choice. Although thematically it fits perfectly with Flooding, it's also kind of.. lame. I mean we have all kinds of Dragons running around, Rains of Fire, Lightnings and Rice? If you want people to get excited about this idea, you probably need to come up with something cooler, maybe even something magical? Maybe like a tree that bears magical fruit or something, I don't know.
I agree that the switch from
to
was a good move. Makes more sense this way. Not sure about the mechanics though. Maybe you should try what Zblader suggested. Like... generate a copy when the owner plays a
card? Um.. maybe not.