I put a few canna leaves in a bucket of water and weighted them down with a rock with the intention of rotting away the non fibrous material. This process is called retting and is what is used in the process of getting linen fiber from flax.

I’ve read that flax only needs a few days of water retting, so after three days I dumped out the water (which was brown but not smelly) and rinsed the canna. There was no appreciable difference. Hm. It appears that canna needs more time than flax. Not surprising since canna is a much more robust plant than flax. I need that bucket, though, so I will find a different container to attempt to retting again.