The Leaves can be trimmed, I let mine flower ,then cut the spent flower stalks right back, leave them alone over the heat of Summer. Then once the days arent so hot, and here in Aust. before "may day" all of mine are lifted, separated, trimmed and replanted ready for next flowering season. This hasnt hurt my plants ability to flower, I actually get more every season this way. The up-side is that you have many plants to either give away or sell each year too.

Cheers, K