The effect of leaf and form in landscapes can not be more dramatically demonstrated by any other perennial as with Gunnera manicata (formerly known as Gunnera eliptica, I think…)
They grow quite fast and very easily as long as they have lots of water and sufficient light.
Despite the size the leaves get and the bad press, they are not very intrusive as they keep their young close to their main stem. Keep an eye open for seedlings though.
I have yet to see a situation where a Gunnera went out of control. I love them.