Posted: 16/12/2014 at 20:59
All the above doubles still produce pollen for the bees. there are forms where the stamen etc have become petaloid and no longer function.
The main reason for removing the old leaves (usually by us in February) is that the plant no longer needs them and they can become infected with various fungi. Removing them does the plant good as it does not have to fight off any pathogens from the leaves.
This of course only applies to the x hybridus types. All the others should only have dead leaves removed as and when you see them, especially H. niger and its cousins.