I have read on the website that it is a good idea to mulch bearded iris with manure. Do I cover the tuber??
No. Keep the tuber clear so that it can get maximum sun.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
The RHS says they are not hungry plants but will appreciate some well-rotted garden compost around but not on their rhizomes. I would have thought manure would be far too rich for them.
Vendée - 20kms from Atlantic coast.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw