That's an interesting question, and for some plants it's always suggested to remove leaves and stems which are going downhill in their natural cycle after flowering just for appearacne sake, but it's thought for some plants, that allowing the stalks to die back naturally recycles the nutrients from those dieing stalks back to the bulbs or the rhizomes etc. I guess I'll have to further research that question. Oftentimes dieing leaves or stems are also thought to place demands on the roots , when in such a declining state thery're using more nutrients than they can contribute by natural photosynthesis, since the leaves are no longer a healthy green.

good luck in trying to find an answer......I've tried master gardners....home depot managers...and the list goes on....seems like everyone has a different answer.....if you do find out....please keep me in mind.....

thanks