It spreads like crazy once it gets started, so you have to keep an eye on it. I put paths and stuff around mine so it stays where I put it. But it can jump over the path or flowers if they are only one wide. Two wide keeps it in.
I have 9 bamboo plants (1 basket full when I harvest it). I forgot to harvest it this last time and so they sprouted. I let them go and the next day they all wilted. They were either next to the cliff, river bank, a full grown bamboo plant or caddy-corner to another bamboo plant or tree. So bamboo plants follow the same planting rules as trees.