Anyone have any experience with these plants? Several of us crazy gardeners here in desert of So Cal have been struggling with this swamp plant. I think I have finally succeeded by planting it in a huge pot and setting it in our pond about 3/4 the way submerged and keeping the leaves misted every few days... it is a gorgeous plant with humongous leaves (over 3-4' across when maturing with the potential for 5-6' across) and bizzare red-brown flowers and petioles covered with bizzare bumps and dull spines. Hope this works since most Gunneras eventually die from the lack of humidity here. But burying one up to it's 'neck' makes them rot... wish me luck.
It is a bog plant, and as long as you can keep the roots wet it will do well, it can be put in full sun and light shade, this plant will grow about 8' tall and like you say have leaves 3' across, i have one, keeping it in a pot will keep it under control, but it may topple over in winds, so get a heavy pot to put it in, if you have a problem with green water in your pond, you will find Gunnera a great help, good luck.