Carol, I have several large clumps of Kniphofia rooperi ‘Villa Noailles’ on the top of a hot dry stone wall. I cut them down to about one third on the top and shorter on the sides when the leaves start to flop. Usually in early spring.( I should really be splitting them now as they have been in for 5 years). Mine flowered in Nov- Jan. Always cut the dead flower stems off and you do need to pull out dead leaves while you are doing the cutting. I think they are fabulous. Very majestic, all those colourful stems of pokers in the winter. However, I don't think all Kniphofia are winter flowering so you would need to check that.