Patty Laughlin of Lorax Landscaping suggests NO fall clean-up in perennial beds. Patty says that, "The leaves and debris provide a haven for good insects through the winter. Uncut perennials allow better root and crown protection (they catch leaves and snow for their insulation), provide food and perches for birds and add winter landscape interest for you."
I took Patty's advice and I am now enjoying the garden even more this fall. The big bluestem is six feet tall. Loose clumps of silky milkweed seeds hang on to their stalk, at least until the next big wind comes along.