Apologies for asking again but I'm still unsure what I can do with this plant.. I feel it's really very congested! I would usually leave it as I love the seed heads but this has just turned into a massive congested look of new and old leaves that are rotting away. I know the plant won't come to any harm to leave it but can I chop this to around 6 inches to let light and air get to it and perhaps divide it? I've seen some small plants of it near by that have self seeded but can I chop and divide it to tidy it up rather than leave until spring?