Long, long ago somebody asked me about uses for Acanthus (bear's breeches). They had looked far and wide, and found nice photos (like those on my site), but no notes about uses whatsoever.
This was years ago.
A few months ago I mentioned that, in passing, to Chris Hedley, as we were ambling about the order beds of Kew Garden (in London).
He said to use the leaf like Plantago.
I wouldn't use the spiny one, though, cos that might be hurtful.
So there you are, wherever you are.
I haven't seen any Acanthuses at all, up here in Finland, so perhaps it doesn't grow here? Or perhaps I've just been blind to it. It looks like a biennial to me, and those can be dicey to grow here over winter: it's cold, icy, dark, and above all, long. (No problem if there's snow cover, but there isn't always - like right now ... it's all melted over the last few days worth of southern winter storms. Ice, check. Promised frost, check. Those are the killers, not the cold and dark.)
But if you have this large beauty in your garden, or growing as a weed all around you, do make a salve and let me know how that works as a woundhealer.
Or make a tea or syrup and tell me about its efficacy in coughs.