I work on removing the old, tatty leaves off the orientalis by New Year- you can often already see the flower buds ready to break by then.
Only this last week have finished removing the spent flower stems off them & the Nigers, plus the odd very tatty leaf off the latter. I grow my Nigers in pots as the only way can keep them in my garden.
The 'Corsican' type- soz cant remember the latest correct name- I remove the old foliage in spring allowing the new shoots to grow- they are the ones that will flower next year, so dont remove those leaves in the winter, or no flowers. Be prepared to stake these big plants too as they grow. The other sorts dont need any staking. J.